Basic Training Manual INDUSTRIAL-DUTY AND COMMERCIAL-DUTY PRODUCTS A Regal Brand
Basic Training Industrial-Duty & Commercial-Duty Electric Motors Gearmotors Gear Reducers AC & DC Drives A Publication Of LEESON Electric Grafton, Wisconsin 53024 U.S.A.
Contents I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Electric Motor History and Principles II. General Motor Replacement Guidelines . . . . . . . . . . . 8 III. Major Motor Types . . . . . . . . . . . . . . . . . . . . . . . . . . 15 AC Single Phase AC Polyphase Direct Current (DC) Gearmotors Brakemotors Motors For Precise Motor Control Permanent Magnet (PMAC) Motors Benefits of PMAC Motor IV. Mechanical Considerations . . . . . . . . . . . . . . . . . . . .
Shaft Grounding Devices Faraday Shield Grounding Brush Shaft Grounding Ring Insulated Bearings Torque Speed Characteristics Individual Branch Circuit Wiring Motor Starters Across the Line Starting of Induction Motors Magnetic Starters Reduced Voltage Starters Primary Resistance Starters Autotransformer Starters Wye-Delta Starting Part Winding Starters Reading a LEESON Model Number Reading a Lincoln Motors Model Number Major Motor Components VI. Metric (IEC) Designations . . . . . . . . . . . . . . . . . .
IX. Gear Reducers and Gearmotors . . . . . . . . . . . . . . . . . 75 Right-Angle Worm Gear Reducers Parallel-Shaft Gear Reducers Gearmotors Installation and Application Considerations Special Environmental Considerations Gear Reducer Maintenance X. Adjustable Speed Drives . . . . . . . . . . . . . . . . . . . . . . 84 DC Drives AC Drives “One Piece” Motor/Drive Combinations AC Drive Application Factors Motor Considerations With AC Drives Routine Maintenance of Electrical Drives XI. Engineering Data .
CHAPTER I Electric Motor History and Principles The electric motor in its simplest terms is a converter of electrical energy to useful mechanical energy. The electric motor has played a leading role in the high productivity of modern industry, and it is therefore directly responsible for the high standard of living being enjoyed throughout the industrialized world.
motors, the placement of the phase winding groups in conjunction with the phase sequence of the power supply line produces a rotating field around the rotor surface. The rotor tends to follow this rotating field with a rotational speed that varies inversely with the number of poles wound into the stator. Single-phase motors do not produce a rotating field at a standstill, so a starter winding is added to give the effect of a polyphase rotating field.
The whole structure of the motor must be rigid to reduce vibration and noise. The stator insulation and coil winding must be done in a precise manner to avoid damaging the wire insulation or ground insulation. And mountings musts meet exacting dimensions. This is especially true for motors with NEMA C face mountings, which are used for direct coupling to speed reducers, pumps and other devices. The electric motor is, of course, the very heart of any machine it drives.
CHAPTER II General Motor Replacement Guidelines Electric motors are the versatile workhorses of industry. In many applications, motors from a number of manufacturers can be used. Major motor manufacturers today make every effort to maximize interchangeability, mechanically and electrically, so that compromise does not interfere with reliability and safety standards. However, no manufacturer can be responsible for misapplication.
Much of this information consists of standards defined by the National Electrical Manufacturers Association (NEMA). These standards are widely used throughout North America. In other parts of the world, the standards of the International Electrotechnical Commission (IEC) are most often used.
Physical and Environmental Consideration Usual Service Conditions Motor ratings apply to motors operating under usual service conditions. NEMA and EEMAC (Electrical Equipment Manufacturers Association of Canada) standards specify usual environmental conditions as: 1. Exposure to an ambient temperature in the range of 0º to 40ºC or when water cooling is used, in the range of 10º to 40ºC. 2. Exposure to an altitude which does not exceed 3300 feet (1000 meters) (see MG1-14.04) 3.
2) Operation where: • Excessive departure from rated voltage or frequency exceeding 10% • Unbalanced Voltage between legs by more than 1% 3) Operation of speeds above the highest rated speed 4) Operation in a poorly ventilated room or an inclined position 5) Operation subjected to: • Torsional impact loads • Repetitive abnormal overloads • Reversing or electric braking Enclosure • • The enclosure for the motor should be chosen to protect it from the expected operating environment See Chapter IV for Enclosu
Efficiency and Economics When selecting a motor for a particular application, both its capital cost and the cost of energy for operation should be considered. With today’s EISA mandates that went into affect on Dec. 19, 2010, we have little choice in selecting the efficiency of the motor, especially if the motor is a 140 frame motor or higher and rated over 1 HP. There are no EISA mandates today for 1- Phase motors.
Nameplate Nameplate data is the critical first step in determining motor replacement. Much of the information needed can generally be obtained from the nameplate. Record all nameplate information; it can save time and confusion. Important Nameplate Data • Catalog number. • Motor model number. • Frame. Designates NEMA frame size dimensions • Type (classification varies from manufacturer to manufacturer). • Phase - single, three or direct current. • HP - horsepower at rated full load speed.
• Maximum ambient temperature in centigrade – usually +40°C (104°F). • Duty - most motors are rated continuous. Some applications, however, may use motors designed for intermittent, special, 15, 30 or 60 minute duty. • NEMA electrical design - B, C and D are most common. Design letter represents the torque characteristics of the motor. • Insulation class - standard insulation classes are B, F, and H. NEMA has established safe maximum operating temperatures for motors.
CHAPTER III Major Motor Types Alternating current (AC) induction motors are divided into two electrical categories based on their power source – single phase and polyphase (three phase). AC Single Phase Types Types of single-phase motors are distinguished mostly by the way they are started and the torque they develop. Shaded Pole motors have low starting torque, low cost, low efficiency, and no capacitors. There is no start switch.
Capacitor Start motors are designed in both moderate and high starting torque types with both having moderate starting current, high breakdown torques. Cap start circuit diagram Moderate-torque motors are used on applications in which starting requires torques of 175% or less or on light loads such as fans, blowers, and light-start pumps. High-torque motors have starting torques in excess of 300% of full load and are used on compressors, industrial, commercial and farm equipment.
A heavy-duty polyphase motor with cast-iron frame. AC Polyphase (Three-Phase) Polyphase induction motors have a high starting torque, power factor, high efficiency, and low current. They do not use a switch, capacitor, relays, etc., and are suitable for larger commercial and industrial applications. Polyphase induction motors are specified by their electrical design type: A, B, C, D or E, as defined by the National Electrical Manufacturers Association (NEMA).
-18- Design E Normal locked rotor torque and current, low slip Design D High locked rotor torque and high slip Design C High locked rotor torque and normal locked rotor current Design B Normal locked rotor torque and normal locked rotor current Design A High locked rotor torque and high locked rotor current Polyphase Characteristics 75-190 275 200-285 70-275 70-275 Locked Rotor Torque (% Rated Load Torque) 60-140 NA 140-195 65-190 65-190 Pull-Up Torque (% Rated Load Torque) 160-200 275
Direct Current (DC) Another commonly used motor in industrial applications is the direct current motor. It is often used in applications where adjustable speed control is required. Permanent magnet DC designs are generally used for motors that produce less than 5 HP. Larger horsepower applications use shuntwound direct current motors. DC motors can be operated from rectified alternating current of from low-voltage battery or generator source.
Gearmotors may be either integral, meaning the gear reducer and motor share a common shaft, or they may be created from a separate gear reducer and motor, coupled together. Integral gearmotors are common in sub-fractional horsepower sizes; separate reducers and motors are more often the case in fractional and integral horsepowers. For more on gear reducers and gearmotors, see Chapter IX.
Permanent Magnet (PMAC) Motors The PMAC (Permanent Magnet AC) motor is traditionally of a more complex construction than the standard induction motor. With the new motor type, the design has been simplified by using powerful permanent magnets to create a constant flux in the air gap, thereby eliminating the need for the rotor windings and brushes normally used for excitation in synchronous motors.
CHAPTER IV Mechanical Considerations Enclosures and Environment Open Drip Proof (ODP) motors have venting in the end frame and/or main frame, situated to prevent drops of liquid from falling into the motor within a 15° angle from vertical. These motors are designed for use in areas that are reasonably dry, clean, well-ventilated, and usually indoors. If installed outdoors, ODP motors should be protected with a cover that does not restrict air flow.
Explosion Proof motors meet Underwriters Laboratories or CSA standards for use in the hazardous (explosive) locations shown by the UL/CSA label on the motor. The motor user must specify the explosion proof motor required. Locations are considered hazardous because the atmosphere contains or may contain gas, vapor, or dust in explosive quantities. The National Electrical Code (NEC) divides these locations into classes and groups according to the type of explosive agent.
-24- ¬ Group C Group D - - - Group C Group D - - - - - - Group IIA, Category G Group IIB, Category G Group IIC, Category G ¬ Group IIC, Category G ¬ Group is not applicable to that Division or Zone, or is not defined. Group is not available from LEESON Electric or Lincoln Motors.
-25- T2A 280OC T2(280) ATEX Explosion Proof - Class I, Group D (Group C as noted) Division 1/Zone 1 Class I Area Classification (Flammable Gases, Vapors or Mists) Division 1/Zone 21 Class II Area Classification* (Combustible Dusts) T3C T3(160) T4 T4 * Class II, Division 2 motors are not available from LEESON Electric / Lincoln Motors, Zone 22 groups are not defined by ATEX.
NEMA Frame/Shaft Sizes Frame numbers are not intended to indicate electrical characteristics such as horsepower. However, as a frame number becomes higher so in general does the physical size of the motor and the horsepower. There are many motors of the same horsepower built in different frames. NEMA (National Electrical Manufacturers Association) frame size refers to mounting only and has no direct bearing on the motor body diameter.
Shaded area denotes dimensions established by NEMA standard MG-1. Other dimensions will vary among manufactures.
NEMA Frame Suffixes C = NEMA C face mounting (specify with or without rigid base) D = NEMA D flange mounting (specify with or without rigid base) H = Indicates a frame with a rigid base having an F dimension larger than that of the same frame without the suffix H.
Types of Mounts Rigid base is bolted, welded, or cast on main frame and allows motor to be rigidly mounted on equipment. Resilient base has isolation or resilient rings between motor mounting hubs and base to absorb vibrations and noise. A conductor is imbedded in the ring to complete the circuit for grounding purposes. NEMA C face mount is a machined face with a pilot on the shaft end which allows direct mounting with the pump or other direct coupled equipment.
Application Mounting For direct-coupled applications, align shaft and coupling carefully, using shims as required under motor base. Use a flexible coupling, if possible, but not as a substitute for good alignment practices. Pulleys, sheaves, sprockets and gears should be generally mounted as close as possible to the bearing on the motor shaft, thereby lessening the bearing load. The center point of the belt, or system of V-belts, should not be beyond the end of the motor shaft.
Motor Guidelines for Belted Applications The information contained in this document is intended to be used for applications where LEESON Electric and Lincoln Motors motors are connected to other equipment through the use of a V-belt drive. These are to be used as guidelines only since LEESON Electric and Lincoln Motors does not warrant the complete drive system.
3. Sheave Location Install sheaves as close to the housings as possible to increase the bearing life of the motor and driven equipment. AVOID AVOID DESIRED DESIRED 4. Belt Tension In general, belt tensions are to be kept as loose as possible while still transmitting the required torque without slipping. Belt tensions must be measured with a belt tension gage. These inexpensive gages may be obtained through belt manufacturers, or distributors.
-33- 1200 rpm 1800 rpm 3600 rpm Min. Max. Belt Min. Max. Belt Min. Max. Belt Motor Sheave Belt # Deflected Sheave Belt # Deflected Sheave Belt # Deflected Hp Dia. (in.) Type of Force Dia. (in.) Type of Force Dia. (in.) Type of Force Belts (lbs.) Belts (lbs.) Belts (lbs.) 0.75 2.2 3VX 1 3.4 2.2 3VX 1 2.2 2.2 3VX 1 1.3 1 2.4 3VX 1 4.0 2.2 3VX 1 3.1 2.2 3VX 1 1.6 1.5 2.4 3VX 2 3.1 2.4 3VX 2 2.1 2.2 3VX 1 2.5 2 2.4 3VX 3 2.8 2.4 3VX 2 2.9 2.4 3VX 1 2.7 3 3.0 3VX 2 2.9 2.4 3VX 3 2.9 2.
Notes: 1. Horsepowers are nameplate motor horsepowers, and RPMs are motor (driver) speeds. 2. NEMA minimum sheave diameters are from NEMA MG 1, Part 14, Table 14-1. 3. Consult LEESON Electric for applications utilizing (1) smaller sheaves and/or more belts than specified (2) variable speed applications (3) values outside these recommendations. 4. Selections are based on a 1.4 service factor, 5 to 1 speed ratio and various Power Transmission Manufacturer’s catalogs used as reference. 5.
CHAPTER V Electrical Characteristics and Connections Voltage, frequency and phase of power supply should be consistent with the motor nameplate rating. A motor will operate satisfactorily on voltage within 10% of nameplate value, or frequency within 5%, or combined voltage and frequency variation not to exceed 10%. Voltage Common 60 hz voltages for single-phase motors are 115 volt, 230 volt, and 115/230 volt. Common 60 hz voltage for three-phase motors are 230 volt, 460 volt and 230/460 volt.
Hertz / Frequency In North America 60 hz (cycles) is the common power source. However, most of the rest of the world is supplied with 50 hz power. Horsepower Exactly 746 watts of electrical power will produce 1 HP if a motor could operate at 100% efficiency, but of course no motor is 100% efficient. A 1 HP motor operating at 84% efficiency will have a total watt consumption of 888 watts. This amounts to 746 watts of usable power and 142 watts loss due to heat, friction, etc. (888 x .84 = 746 = 1 HP).
Insulation Class Insulation systems are rated by standard NEMA classifications according to maximum allowable operating temperatures. They are as follows: Class Maximum Allowed Temperature* A 105°C (221°F) B 130°C (266°F) F 155°C (311°F) H 180°C (356°F) * Motor temperature rise plus maximum ambient Generally, replace a motor with one having an equal or higher insulation class. Replacement with one of lower temperature rating could result in premature failure of the motor.
For easy reference, standard NEMA service factors for various horsepower motors and motor speeds are shown in this table. HP 1 /, / / / / 1 1 / up 1 6 1 3 4, 1 3 2 4 1 2 FOR DRIP PROOF MOTORS Service Factor Synchronous Speed (RPM) 3600 1.35 1.25 1.25 1.25 1.15 1800 1.35 1.25 1.25 1.15 1.15 1200 1.35 1.25 1.15 1.15 1.15 900 1.35 1.25 1.15 1.15 1.15 The NEMA service factor for totally enclosed motors is 1.0. However, many manufacturers build TEFC with a 1.15 service factor.
overloaded due to additional weight of product added to the conveyor, the controller should notice a change in pulses from the encoder, for the speed of the conveyor slows down from this additional weight, and the controller will send a signal to the motor to speed up to compensate for this load change. Once the load has been returned to the standard expected load, the control will again see a signal from the encoder and will slow the motor down to the needed speed.
Shaft Grounding Devices Shaft grounding is recommended (NEMA MG1 31.4.4.3) as an effective means of bearing protection for motors operated from inverter power. Shaft voltage occurs in motors powered by variable frequency inverters (VFD) These VFDs induce shaft voltages onto the shaft of the driven motor because of the extremely high speed switching of the insulated gate bipolar transistors (IGBTs) which produce the pulse width modulation used to control AC motors.
Insulated Bearings Insulated or ceramic bearings eliminate the path to ground through the bearing for current to flow. Torque-speed Characteristics of Motors: • The amount of torque produced by a motor generally varies with speed. • This Torque-Speed characteristic depends on the type and design of a motor, and is often shown on a Torque-Speed graph. % RATED TORQUE % RATED SPEED Figure 2.
ual Reset: This line-interrupting protector has an rnal button that must be pushed to restore power to motor. Use where unexpected restarting would be ardous, Individual as on saws, conveyors, and Branchcompressors Circuit Wiring r machinery. varies with the frequency of the pulses introd output voltage.
Chart 2 WIRE GAGE Three Phase Motors - 230 & 460 Volts -43-
Motor Starters As their name implies, motor starters apply electric power to a motor to begin its operation. They also remove power to stop the motor. Beyond merely switching power on and off, starters include overload protection, as required by the National Electrical Code. The code also usually requires a disconnect and short circuit protection on motor branch circuits.
Magnetic Starters • Magnetic starters are used with larger motors or where greater control is desired. The main element of the starter is the contactor, which is a set of contacts operated by an electromagnetic coil. Energizing the coil causes the contacts A to close, allowing large currents to be initiated and interrupted by a control signal.
Reduced Voltage Starters • If the driven load or the power distribution system cannot accept a full voltage start, some type of reduced voltage or “soft” starting scheme must be used. • Typical reduced voltage starters are: primary resistance starters, autotransformers, part winding starters, wye-delta and solid state starters. • These devices can only be used where low starting torque is acceptable.
Autotransformer Starters • An autotranformer is a single winding transformer on a laminiated core with taps at various points on the winding. The taps are usually expressed as a percentage of the total number of turns and thus percentage of applied voltage output. • Three autotransformers are connected in a wye configuration or two in an open delta configuration, with taps selected to provide adequate starting current. • The motor is first energized at a reduced voltage by closing contacts A.
Wye-Delta Starting • Wye-Delta Starting can be used with motors where all six leads of the stator winding are available (on some motors only three leads are accessible). Motor windings Figure 4.5 Wye-Delta Starter • By first closing contacts A and B, the windings are connected in a wye configuration which presents 57% of rated voltage to the motor. • Full voltage is then applied by reconnecting the motor in a delta configuration by closing contacts C and opening those at A.
Part Winding Starters • Part winding starters are sometimes used on motors wound for dual voltage operation such as a 230/460 V motor. These motors have two sets of winding connected in parallel for low voltage, and in series for high voltage operation. • When used on the lower voltage, they can be started by first energizing only one winding, limiting starting current and torque to approximately one half of the full voltage values.
Reading a LEESON Model Number There is no independently established standard for setting up a motor’s model number, but the procedure is typically tied to descriptions of various electrical and mechanical features. While other manufacturers use other designations, here is how LEESON model numbers are configured. EXAMPLE: Position No. Sample Model No. 1 2 A B 3 4 4 5 6 7 C 17 D B 8 1 9 10 A (A-Z) Position 1: U.L. Prefix A— Auto protector. U.L.
NOTES -51-
Reading a Lincoln Motors Model Number There is no independently established standard for setting up a motor’s model number, but the procedure is typically tied to descriptions of various electrical and mechanical features. While other manufacturers use other designations, here is how Lincoln Motors model numbers are configured. EXAMPLE: Position No. Sample Model No. A B C D E F G H SRF 4 S 0.
Position G: Electrical Type (Single Phase Only): [cont’d] Position H: Options/Modifications: (cont’d) Commonly used voltage codes: 60 Hz 61 = 230/460 V 62 = 200/400 63 = 208 64 = 460 65 = 575 66 = 230 67 = 440 68 = 380 69 = 480 6003 = 220/380 6004 = 220/440 6020 = 2300 6021 = 4000 6024 = 2300/4000 6026 = 208-230/460 6027 = 115/230 6028 = 115/208-230 6029 = 208-220/440 Q15_ Q20 Q40 QS10 QS11 QS12 RB T1 T5 TD1,2 TD4 TD6 TP1 TP2 TX1 W_ X_ 50 Hz 51 = 220/380 V 52 = 240/415
Major Components of Rear Endshield Fan Guard** External Fan** Starting Switch* (Stationary) Connection Box Nameplate -54-
an Electric Motor Capacitor Case* * SINGLE PHASE ONLY ** TEFC ONLY Capacitor* Frame Stator Starting Switch* (Rotating) Internal Fan Shaft Front Endshield Cast Rotor Base Bearing End Ring -55-
CHAPTER VI Metric (IEC) Designations and Dimensions The International Electrotechnical Commission (IEC) is a European-based organization that publishes and promotes worldwide mechanical and electrical standards for motors, among other things. In simple terms, it can be said that IEC is the international counterpart to the National Electrical Manufacturers Association (NEMA), which publishes the motor standards most commonly used throughout North America.
KW/HP** Frame Dimensions in Millimeters Assignments 3 Phase – TEFC IEC D E F H U BA N-W NEMA 2 Pole 4 Pole 6 Pole 56 56 45 35.5 5.8 9 36 20 – – – – – – – – – – – – – 63 63 NA – 50 – 40 – 7 – 11 – 40 – 23 – 71 71 42 66.7 56 44.5 45 21.4 7 7.1 14 9.5 45 52.4 30 – .55 3/4 .37 1/2 – – 80 48 80 76.2 62.5 54 50 34.9 10 8.7 19 12.7 50 63.5 40 38.1 1.1 1-1/2 .75 1 .55KW 3/4HP 90S 90 56 88.9 70 61.9 50 38.1 10 8.7 24 15.
IEC Enclosure Protection Indexes Like NEMA, IEC has designations indicating the protection provided by a motor’s enclosure. However, where NEMA designations are in words, such as Open Drip Proof or Totally Enclosed Fan Cooled, IEC uses a two-digit Index of Protection (IP) designation. The first digit indicates how well-protected the motor is against the entry of solid objects; the second digit refers to water entry.
IEC Cooling, Insulation and Duty Cycle Indexes IEC has additional designations indicating how a motor is cooled (twodigit IC codes). For most practical purposes, IC 01 relates to a NEMA open design, IC 40 to Totally Enclosed Non-Ventilated (TENV), IC 41 to Totally Enclosed Fan Cooled (TEFC), and IC 48 to Totally Enclosed Air Over (TEAO). IEC winding insulation classes parallel those of NEMA and in all but very rare cases use the same letter designations. Duty cycles are, however, different.
S8 Continuous operation with periodic changes in load and speed. Sequential, identical duty cycles of start, run at constant load and given speed, then run at other constant loads and speeds. No rest periods. IEC Design Types The electrical performance characteristics of IEC Design N motors in general mirror those of NEMA Design B – the most common type of motor for industrial applications. By the same token, the characteristics of IEC Design H are nearly identical to those of NEMA Design C.
CHAPTER VII Motor Maintenance Motors, properly selected and installed, are capable of operating for many years with a reasonably small amount of maintenance. Before servicing a motor and motor-operated equipment, disconnect the power supply from motors and accessories. Use safe working practices during servicing of the equipment. Clean motor surfaces and ventilation openings periodically, preferably with a vacuum cleaner.
Relubrication Intervals Chart For Motors Having Grease Fittings Hours of Service HP Range Suggested Per Year Relube Interval 5000 1/18 to 7 1/2 5 years 10 to 40 3 years 50 to 100 1 year Continuous Normal to 7 1/2 2 years Applications 10 to 40 1 year 50 to 100 9 months Seasonal Service All 1 year Motor is idle for (beginning of 6 months or more season) Continuous high ambient, high vibrations, or where shaft end is hot 1/8 to 40 50 to 150 6 months 3 mont
-63-
-64- Motor takes too long to accelerate. Verify brush length. Inspect bearings for proper service. Noisy or rough bearings should be replaced. Brushes are worn. Bearings may be defective. Verify that the brushes are properly seated and measure their length against the recommended brush length chart. Brushes may not be seated properly or worn beyond their useful length. The accel trim pot of the controller should be adjusted. Inspect the armature for an open connection.
-65- Replace fuse or reset breaker. Disassemble motor and inspect windings and internal connections. A blown stator will show a burn mark. Motor must be replaced or the stator rewound. Fan guard bent and contacting fan. Fuse or circuit breaker tripped. Stator is shorted or went to ground. Motor will make a humming noise and the circuit breaker or fuse will trip. Motor had been running, then fails to start. Inspect to see that the load is free.
-66- Incorrect wiring. Motor overload protector Load too high. continually trips. Motor runs in the wrong rotation. Voltage too low. Verify that the load is not jammed. If motor is a replacement, verify that the rating is the same as the old motor. If previous motor was a special design, a stock motor may not be able to duplicate the performance. Remove the load from the motor and inspect the amp draw of the motor unloaded.
-67- Test motor by itself. If bearings are bad,you will hear noise or feel roughness. Replace bearings. Add oil if the bearing is a sleeve bearing type or replace bearings. Add grease if bearings have grease fittings. Inspect motor by itself with no load attached. If it feels rough and vibrates but the bearings are good, it may be that the rotor was improperly balanced at the factory. Rotor must be replaced or rebalanced. With the motor disconnected from power turned shaft.
-68- Verify duty cycle. Capacitor manufactures recommend no more than 20, three-second starts per hour. Install capacitor with higher voltage rating, or add bleed resistor to the capacitor. Verify that voltage to the motor is within 10% of the nameplate value. If the motor is rated 208-230V, the deviation must be calculated from 230V. Replace switch. The motor is being cycled too frequently. Voltage to motor is too low.
CHAPTER VIII Common Motor Types and Typical Applications Alternating Current Designs Single Phase * Rigid Base Mounted * Capacitor Start * Totally Enclosed Fan Cooled (TEFC) & Totally Enclosed Non-Vent (TENV) General purpose including compressors, pumps, fans, farm equipment, conveyors, material handling equipment and machine tools.
Wash-Thru and Multiguard Motors Used in applications involving moisture, vibration, dust and some chemical contact. The motor’s windings are impregnated and encapsulated in a thermosetting that protects them from contaminants for long motor life. Automotive Duty Motors Suited for a wide variety of tough applications found in automotive manufacturing facilities and other industries utilizing U-Frame motors. Meets or exceeds General Motors GM-7EH and –7EQ, Ford EM1 and Chrysler NPEM-100 specifications.
Resilient Mounted * Single & Three Phase * Two Speed * Two Winding * Variable Torque: Belted or fan-on-shaft applications. Rigid Mounted * Totally Enclosed Air Over (TEAO) * Single & Three Phase Dust-tight motors for shaft-mounted or belt-driven fans. The motor depends upon the fan’s airflow to cool itself.
Compressor Duty * Single & Three Phase Air compressor, pump-fan and blower duty applications which require high breakdown torque and overload capacity matching air compressor loading characteristics. Woodworking Motors * Single Phase * TEFC High torques for saws, planers and similar woodworking equipment.
Milk Transfer Pump Motor * Rigid Base * Single Phase * TENV Replacement in dairy milk pumps. Grain Stirring Motors * Rigid Base * Single Phase * TEFC Designed to operate inside agricultural storage bins for stirring grain, corn, and other agricultural products during the drying and storage process. Irrigation Drive Motors * C Face Less Base * Three Phase * TEFC For center pivot irrigation systems exposed to severe weather environments and operating conditions.
Direct Current Designs High-Voltage, SCR-Rated Brush-Type * Permanent Magnet Field * C Face With Removable Base * TEFC Generally used for conveyors, machine tools, hoists or other applications requiring smooth, accurate adjustable-speed capabilities through the use of thyristor-based controls, often with dynamic braking and reversing also required. Usually direct-coupled to driven machinery, with the motor often additionally supported by a base for maximum rigidity.
CHAPTER IX Gear Reducers and Gearmotors A gear reducer, also called a speed reducer or gear box, consists of a set of gears, shafts and bearings that are factory-mounted in an enclosed, lubricated housing. Gear reducers are available in a broad range of sizes, capacities and speed ratios. Their job is to convert the input provided by a “prime mover” into output of lower RPM and correspondingly higher torque.
has been shown to result in long life, smooth operation, and noise levels acceptable for industrial environments. The number of threads in the worm shaft, related to the number of teeth in the worm gear, determine the speed reduction ratio. Single-reduction worm gear reducers are commonly available in ratios from approximately 5:1 through 60:1. A 5:1 ratio means that motor input of 1750 RPM is converted to 350 RPM output. A 60:1 ratio brings output RPM of the same motor to 29 RPM.
Gearmotors Three-phase NEMA C face AC motor combined with flanged worm gear reducer results in a “workhorse” industrial gearmotor. This straightforward mounting approach is common with motors ranging in sizes from fractional through 20 HP and larger. An electric motor combined with a gear reducer creates a gearmotor. In sub-fractional horsepower sizes, integral gearmotors are the rule – meaning the motor and the reducer share a common shaft and cannot be separated.
NEMA C flange reducers are of two basic types based on how the motor and reducer shafts are coupled. The most straightforward type, and the most commonly used in smaller horsepower applications, has a “quill” input – a hollow bore in the worm into which the motor’s shaft is inserted. The other type, involving a reducer having a solid input shaft, requires a shaft-to-shaft flexible coupling, as well as an extended NEMA C flange to accommodate the combined length of the shafts.
Reducers having hollow output shafts are usually shaft-mounted to the driven load. If no output flange or secondary base is used, a reaction arm prevents the reducer housing from rotating. Hollow output shaft reducer with reaction arm mounted. This model also has quill input and shallow NEMA C input flange. Do not mount reducers with the input shaft facing down. Other than that, they may generally be mounted in any orientation.
Output Speed and Torque: These are the key criteria for matching a gear reducer to the application needs. Center Distance: The basic measurement or size reference for worm gear reducers. Generally, the larger the center distance, the greater the reducer capacity. Center distance is measured from the centerline of the input shaft to the centerline of the output shaft. Horsepower: A reducer’s input horsepower rating represents the maximum prime mover size the reducer is designed to handle.
continuously based on its ability to dissipate the heat caused by operating friction. In practice, the mass of a cast iron reducer housing and its oil lubrication system provide sufficient heat dissipation so that mechanical and thermal ratings are essentially equal. Aluminum housed or greaselubricated reducers have less heat dissipation mass and therefore require consideration of thermal rating.
Service Factor Conversions for Reducers With Electric or Hydraulic Motor Input Duration of Service (Hours per day) Occasional 1/2 Hour Uniform Load Moderate Shock --* Extreme Shock 1.0 1.25 Less than 3 Hours 1.0 1.0 1.25 1.50 3 - 10 Hours 1.0 1.25 1.50 1.75 1.25 1.50 1.75 2.00 Over 10 Hours --* Heavy Shock * Unspecified service factors should be 1.00 or as agreed upon by the user and manufacturer.
Gear Reducer Maintenance Industrial gear reducers require very little maintenance, especially if they have been factory-filled with quality, synthetic lubricant to a level sufficient for all mounting positions. In most cases, oil change will not be necessary over the life of the reducer. It is recommended that oil be changed only if repair or maintenance needs otherwise dictate gearbox disassembly.
CHAPTER X Adjustable Speed Drives By definition, adjustable speed drives of any type provide a means of variably changing speed to better match operating requirements. Such drives are available in mechanical, fluid and electrical types. The most common mechanical versions use combinations of belts and sheaves, or chains and sprockets, to adjust speed in set, selectable ratios – 2:1, 4:1, 8:1 and so forth. Traction drives, a more sophisticated mechanical control scheme, allow incremental speed adjustments.
There are two basic drive types related to the type of motor controlled – DC and AC. A DC direct current drive controls the speed of a DC motor by varying the armature voltage (and sometimes also the field voltage). An alternating current drive controls the speed of an AC motor by varying the frequency and voltage supplied to the motor. DC Drives Direct current drives are easy to apply and technologically straightforward.
PWM types have three elements. The first converts AC to DC, the second filters and regulates the fixed DC voltage, and the third controls average voltage by creating a stream of variable width DC pulses. The filtering section and higher level of control modulation account for the PWM drive’s improved performance compared with a common SCR drive. AC Drives AC drive operation begins in much the same fashion as a DC drive. Alternating line voltage is first rectified to produce DC.
combined with feedback devices such as tachometers, encoders and resolvers in a closed-loop system, are continuing to replace DC drives in demanding applications. “Sub-micro” drives provide a wide array of features in a very small package. By far the most popular AC drive today is the pulse width modulated type.
Size constraints limit integrated drive and motor packages to the smaller horsepower ranges and require programming by remote keypad, either hand-held or panel mounted. Major advantages are compactness and elimination of additional wiring. One-piece motor and drive combinations can be a pre-packaged solution in some applications. Unit shown incorporates drive electronics and cooling system in a special housing at the end of the motor.
torque applications, including conveyors, positive displacement pumps, extruders, mixers or other “machinery” require the same torque regardless of operating speed, plus extra torque to get started. Here, high overload capacity is required. Smaller-horsepower drives are often built to handle either application. Typically, only a programming change is required to optimize efficiency (variable volts-to-hertz ratio for variable torque loads, constant volts-tohertz ratio for constant torque loads).
Drives, like any power conversion device, create certain power disturbances (called “noise” or “harmonic distortion”) that are reflected back into the power system to which they are connected. These disturbances rarely affect the drive itself but can affect other electrically sensitive components.
Speed Setpoint Drive Status RUN > 56.00 HZ Speed Units Direction (Forward) Percent Load Drive Status RUN > 85% Direction (Forward) Speed Setpoint Drive Status FAULT : OVERLOAD Examples of operating and diagnostic displays in a modern AC drive.
Motor Considerations With AC Drives One drawback to pulse width modulated drives is their tendency to produce voltage spikes, which in some instances can damage the insulation systems used in electric motors. This tendency is increased in applications with long cable distances (more than 50 feet) between the motor and drive and with higher-voltage drives. In the worst cases, the spikes can literally “poke a hole” into the insulation, particularly that used in the motor’s windings.
Constant-speed blower kits can be added in the field, providing additional cooling to motors operated at low RPM as part of an adjustable speed drive system. Routine Maintenance of Electrical Drives Major maintenance, troubleshooting and repair of drives should be left to a qualified technician, following the drive manufacturer’s recommendations. However, routine maintenance can help prevent problems.
CHAPTER XI Engineering Data Temperature Conversion Table Locate known temperature in °C/°F column. Read converted temperature in °C/°F column. °C °C/°F °F °C °C/°F °F °C °C/°F °F -45.4 -50 -58 15.5 60 140 76.5 170 338 -42.7 -45 -49 18.3 65 149 79.3 175 347 -40 -40 -40 21.1 70 158 82.1 180 356 -37.2 -35 -31 23.9 75 167 85 185 365 -34.4 -30 -22 26.6 80 176 87.6 190 374 -32.2 -25 -13 29.4 85 185 90.4 195 383 -29.4 -20 -4 32.2 90 194 93.
Mechanical Characteristics To Find: Use: Torque in Inch-Pounds HP x 63,025 Converting Torque Units Inch-Pounds and Newton Meters Torque (lb. in.) = 8.85 x Nm or = 88.5 x daNm RPM Torque (Nm) = lb. in. Torque (lb. in.) x RPM Horsepower 8.85 63,025 Torque (daNm) = lb. in. 88.5 120 x Frequency RPM Number of Poles Electrical Characteristics To Find: Use: SIngle Phase Or: Three Phase Amperes HP x 746 Knowing HP E x Eff x PF 1.73 x E x Eff x PF Amperes kW x 1000 Knowing kW E x PF 1.
Fractional/Decimal/Millimeter Conversion Fraction Decimal Millimeter Fraction Decimal Millimeter MM Inch 1/64 - .015625 - 0.397 33/64 - .515625 - 13.097 1 - .039 1/32 - .03125 17/32 - .53125 - 13.494 2 - .0790 3/64 - .046875 - 1.191 35/64 - .546875 - 13.891 3 - .1181 1/16 - .0625 9/16 - 14.288 4 - .1575 5/64 - .078125 - 1.984 37/64 - .578125 - 14.684 5 - .1969 3/32 - .09375 19/32 - .59375 - 15.081 6 - .2362 7/64 - .109375 - 2.778 39/64 - .609375 - 15.478 7 - .
CHAPTER XII Glossary Actuator: A device that creates mechanical motion by converting various forms of energy to rotating or linear mechanical energy. Adjustable Speed Drive: A mechanical, fluid or electrical device that variably changes an input speed to an output speed matching operating requirements. AGMA (American Gear Manufacturers Association): Standards setting organization composed of gear products manufacturers and users.
Bearings: Sleeve: Common in home-appliance motors. Ball: Used when high shaft load capacity is required. Ball bearings are usually used in industrial and agricultural motors. Roller: Use on output shafts of heavy-duty gear reducers and on some high-horsepower motors for maximum overhung and thrust load capacities. Breakdown Torque: The maximum torque a motor can achieve with rated voltage applied at rated frequency, without a sudden drop in speed or stalling.
Counter Electromotive Force: Voltage that opposes line voltage caused by induced magnetic field in a motor armature or rotor. Current, AC: The power supply usually available from the electric utility company or alternators. Current, DC: The power supply available from batteries, generators (not alternators), or a rectified source used for special applications. Duty Cycle: The relationship between the operating time and the resting time of an electric motor.
Foot-Pound: Energy required to raise a one-pound weight against the force of gravity the distance of one foot. A measure of torque. Inchpound is also commonly used on smaller motors and gear reducers. An inch-pound represents the energy needed to lift one pound one inch; an inch-ounce represents the energy needed to lift one ounce one inch. Form Factor: Indicates how much AC component is present in the DC output from a rectified AC supply. Unfiltered SCR (thyristor) drives have a form factor (FF) of 1.40.
Hertz: Frequency, in cycles per second, of AC power; usually 60 hz in North America, 50 hz in the rest of the world. Named after H. R. Hertz, the German scientist who discovered electrical oscillations. High Voltage Test: Application of a voltage greater than the working voltage to test the adequacy of motor insulation; often referred to as high potential test or “hi-pot.” Horsepower: A measure of the rate of work. 33,000 pounds lifted one foot in one minute, or 550 pounds lifted one foot in one second.
Insulation: In motors, classified by maximum allowable operating temperature. NEMA classifications include: Class A = 105°C, Class B = 130°C, Class F = 155°C and Class H = 180°C. Input Horsepower: The power applied to the input shaft of a gear reducer. The input horsepower rating of a reducer is the maximum horsepower the reducer can safely handle. Integral Horsepower Motor: A motor rated one horsepower or larger at 1800 RPM.
Mounting: The most common motor mounts include: rigid base, resilient base C face or D flange, and extended through bolts. (See Chapter IV for additional details). Gear reducers are similarly basemounted, flange-mounted, or shaft-mounted. National Electric Code (NEC): A safety code regarding the use of electricity. The NEC is sponsored by the National Fire Protection Institute. It is also used by insurance inspectors and by many government bodies regulating building codes.
PMAC (Permanent Magnet AC): Motors that use magnets imbedded in the rotors and is a synchronous motor, meaning that the rotor spins at the same speed as the motor’s internal rotating magnetic field. This offers greater efficiency and better dynamic performance. Polarity: As applied to electric circuits, polarity indicates which terminal is positive and which is negative. As applied to magnets, it indicates which pole is north and which pole is south.
Reactance: The opposition to a flow of current other than pure resistance. Inductive reactance is the opposition to change of current in an inductance (coil of wire). Capacitive reactance is the opposition to change of voltage in a capacitor. Rectifier: A device or circuit for changing alternating current (AC) to direct current (DC). Regenerative Drive: A drive that allows a motor to provide both motoring and braking torque. Most common with DC drives.
Service Factor for Motors: A measure of the overload capacity built into a motor. A 1.15 SF means the motor can deliver 15% more than the rated horsepower without injurious overheating. A 1.0 SF motor should not be loaded beyond its rated horsepower. Service factors will vary for different horsepower motors and for different speeds. Short Circuit: A fault or defect in a winding causing part of the normal electrical circuit to be bypassed, frequently resulting in overheating of the winding and burnout.
Thermistors: Are conductive ceramic materials, whose resistance remains relatively constant over a broad temperature range, then changes abruptly at a design threshold point, creating essentially a solid-state thermal switch. Attached control modules register this abrupt resistance change and produce an amplified output signal, usually a contact closure or fault trip annunciation. Thermistors are more accurate and faster responding than thermostats.
Transformer: Used to isolate line voltage from a circuit or to change voltage and current to lower or higher values. Constructed of primary and secondary windings around a common magnetic core. Underwriters Laboratories (UL): Independent United States testing organization that sets safety standards for motors and other electrical equipment. Vector Drive: An AC drive with enhanced processing capability that provides positioning accuracy and fast response to speed and torque changes.
IMPORTANT INFORMATION Please Read Carefully This Basic Training Manual is not intended as a design guide for selecting and applying LEESON electric motors, gear drive products, or adjustable frequency drives. It is intended as a general introduction to the concepts and terminology used with the products offered by LEESON. Selection, application, and installation of LEESON electric motors, gearmotors, and drives should be made by qualified personnel.
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