LDH400P 400W DC Electronic Loads INSTRUCTION MANUAL
Contents 1. Introduction ................................................................................................... 4 2. Specification ................................................................................................. 5 3. Safety ............................................................................................................ 9 4. Installation ...................................................................................................10 4.1 4.2 4.3 4.4 4.
7.17 8. Utilities Menu .................................................................................................................... 26 Analogue Remote Control ........................................................................... 27 8.1 8.2 9. Remote Voltage Control ................................................................................................... 27 Remote Level Select ........................................................................................................
Full operating and programming instructions for this instrument can be found in the appropriate product folder of the accompanying CD-ROM. This information can also be downloaded from the support page of the Aim-TTi website, http://www.aimtti.com/support. This manual is 48511-1830 Issue 1 Français 14. Sécurité ........................................................................................................
1. Introduction This DC electronic load is for use in investigating the behaviour of many different types of high voltage DC power sources such as PFCs, batteries, solar cells, fuel cells or wind generators, as well as electronic power supply units. The load inputs are rated to CAT II (300V). This allows for PFCs and mains connected power supplies to be directly tested using the electronic load without the need for an isolation transformer.
2. Specification Accuracy specifications apply for 18°C – 28ºC, using the rear panel terminals, after 30 minutes operation at the set conditions. Setting accuracies apply with slew rate at the ‘Default’ setting. INPUT Maximum Input Ratings Current: 16 Amps max. through the front and rear panel terminals. Voltage: 500 Volts max. while conducting current. Power: 400 Watts max. up to 28ºC, derating to 360 watts at 40ºC. Minimum Operating Voltage: 10V.
Constant Conductance Mode (CG) Conductance Range: 0·001 to 1 A/V (1 mA/V resolution) Setting Accuracy: ± 0·5% ± 2 digits ± 30 mA (V > 25 Volts). Regulation: < 2% for 90% load power change (V > 25 Volts). Temperature Coefficient: < (±0·04% ± 5 mA) per ºC. (1) Slew Rate Range: 0·1 A/V per s to 10 A/V per ms. (2) Minimum transition time: 150 µs. TRANSIENT CONTROL Transient Generator Pulse Repetition Rate: Pulse Duty Cycle: Setting Accuracy: Adjustable from 0·01Hz (100 seconds) to 10kHz.
CURRENT MONITOR OUTPUT Output Terminals: Output Impedance: Scaling: Accuracy: Isolation: Bandwidth limit (-3dB): BNC (chassis ground) on front panel or terminal block on rear panel. 600Ω nominal, for >1MΩ load (e.g. oscilloscope). 250mV per Amp (4 Volts full scale). ± 0·5% ± 5mV. CATII (300V) to load negative. 40kHz. REMOTE CONTROL Digital Remote Interfaces The unit provides LAN, USB, GPIB and RS232 interfaces for full remote control.
PROTECTION Excess Power: Protection Current: Excess Current: Protection Voltage: Excess Voltage: Temperature: Reverse Polarity: The unit will attempt to limit the power to 430 Watts; if this fails the unit will trip into the fault state at 460 Watts. The input is disabled if the measured current exceeds a user set limit. The unit will trip into the fault state at nominally 20 Amps. The unit is protected by fuses that protect the unit against currents that exceed 20A.
3. Safety This instrument is Safety Class I according to IEC classification and has been designed to meet the requirements of EN61010−1 (Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory Use). It is an Installation Category II instrument intended for operation from a normal single phase supply. This instrument has been tested in accordance with EN61010−1 and has been supplied in a safe condition.
4. Installation 4.1 Mains Operating Voltage The operating voltage of the instrument is shown on the rear panel. Should it be necessary to change the operating voltage from 230V to 115V or vice-versa, proceed as follows: 1. 2. 3. 4. 5. 6. 7. 8. 4.2 Disconnect the instrument from all voltage sources, including the mains and all inputs. Remove the screws which hold the case upper to the chassis and lift off. Unplug all cable connectors from the power supply PCB (don’t pull on the wires).
4.5 4.5.1 Fuses Current Range Fuses The unit is protected by two 10A fuses that protect the unit against currents that exceed 20A. This is primarily as a protection against high power sources with a current capability of >20A being connected to the load with reverse polarity. The replacement fuse must be a 10x38mm 10A 1kVdc rated HRC fuse. To replace a fuse: 4.5.2 1. Disconnect the instrument from all voltage sources. 2. Remove the screws retaining the fan guard. 3.
5. Connections 5.1 Front Panel Connections 5.1.1 Load Input The INPUT terminals for the load circuit on the front panel accept 4mm plugs. Their maximum current rating is 16 Amps. Do not use both the front panel and rear panel terminals simultaneously. The wiring and connection arrangement must be capable of supporting the current required. The load circuit is isolated from ground, with a rating of CATII (300V), but it is essential to observe safe insulation practice.
5.2.2.2 Oscillator Sync Output The SYNC OUTPUT is a TTL/CMOS (5V) output driven by the signal from the internal oscillator; this output is chassis ground referenced. There is a 1kΩ series protection resistor. 5.2.2.3 Remote Control Voltage Input The CONTROL VOLTAGE terminals are used in two operating modes of the instrument: In EXTERNAL VOLTAGE mode an analogue signal applied here sets the level of the load; the scaling is 4 Volts full scale.
6. Initial Operation This instrument provides a controllable DC load (a power sink) intended for testing all forms of DC power supply including PFCs, batteries, photo-voltaic cells, fuel cells, turbines and generators as well as electronic power supply units. 6.1 Organisation of this manual The paragraphs below are intended to briefly introduce the particular features of this instrument and the terminology used in this manual. More technical details are given in later chapters of the manual.
6.6 Voltage and Current Limit Conditions The unit has provision for the user to specify limits on the permitted measured value of voltage or current. If either of these limits is exceeded then the input will be disabled. 6.7 Power Limit The unit continuously monitors the internal power dissipation and varies the speed of the fan accordingly.
6.10 Connecting the Load to the Source The INPUT terminals of the load must be connected to the source to be tested using sufficiently low resistance and low inductance connections. Inductance in the interconnection can have a significant adverse impact on the stability of the source and load combination. The wiring should be as short and as thick as possible.
7. Front Panel Operation In this manual, front panel labels are shown as they appear, in capitals, e.g. LEVEL SELECT. Individual key names are shown in bold, e.g. Transient, and the blue soft-keys are referred to by their present function, as labelled on the bottom line of the display, shown in bold italics, e.g. Limits. Text or messages displayed on the LCD are shown in bold, e.g. Enabled, Utilities. 7.1 Keys and ∆ Adjust The front panel keys are divided into four areas: ① The numeric keys.
7.2 The Display and the Home Screen All parameter settings and meter readings are shown on the backlit liquid crystal display (LCD). At power up the instrument initialises to the home screen, which is the normal display during operation of the unit. This screen displays all of the load meter readings and the most important load parameter settings as described below, and is also the top level of the soft-key driven menu structure.
7.2.4 [D] Soft-Keys The soft-keys are the six blue keys found directly below the LCD. The function of each of these keys changes as the instrument is operated. The available function is shown on the bottom line of the display in a tab above each key. If any of the keys have no functionality in a particular menu then the tab is lowered to show it is inactive.
7.3 General Numeric Entry of Parameters All user modifiable load parameters can be set using the numeric keypad. The desired parameter is first selected from the menu using the soft-keys. The display then changes to show the parameter entry screen which indicates the name of the parameter, its present value prior to editing, and in most cases the entry limits and resolution. A message prompting for the entry of the new value is shown.
Changing the load mode while the input is enabled will trip a fault detector and cause the input to be disabled before the change is implemented. 7.6 Selection of Load Mode The first action in configuring the unit for a particular application is to choose the load mode, which determines how the current drawn by the load varies with the applied voltage (V). The Mode soft-key on the home screen opens a menu offering the various modes listed in the table below.
7.9 Slow Start The purpose of the slow start circuit is to ramp the demand of the load up slowly from zero to the final value. The rate of rise is determined by the Slew Rate setting. The ramp starts either when the Input is Enabled, or when the voltage from the attached source passes the level of the Dropout Voltage setting. When the Input is Disabled the demand will ramp back down to provide a slow stop (assuming, of course, that the source voltage remains active).
7.12 Transient Frequency The repetition rate of the internally timed transients can be set in terms of frequency or period. Pressing the Freq or Period soft-key on the Transient menu opens the Frequency and Period setting menu. A new value can be entered, in the present representation, in the usual manner. Two soft-keys labelled Freq and Period allow the alternative representation to be chosen. Press the Back soft-key to return to the transient menu or the Home key to return to the home screen.
The bandwidth of the power stages of the load is reduced (by changing the compensation networks) when the slew rate is set to less than 0·1% of the maximum slew rate for the given load mode. For example, in constant current mode, the maximum slew rate setting is 500A/ms, so the bandwidth is reduced when the slew rate is set < 500A/s. This change is made even if the transient facilities are not being used, and alters the dynamic behaviour of the unit.
7.16 Store and Recall Facilities The instrument is able to store and recall up to 30 user defined sets of load parameters in non-volatile memory. Each memory location holds all the parameter settings – load Mode, active level, Level A value, Level B value, Dropout Voltage level, transient Frequency, Duty and Slew Rate and the state of Slow start. Both the store and recall menus display a preview of the parameters that are already stored within each memory location.
7.17 Utilities Menu Pressing the Utilities soft-key on the home screen gives access to four sub-menus to configure various instrument settings and preferences. Instruments fitted with Digital Remote Control interfaces have a fifth sub-menu. The selection can be made using either the ▲ or ▼ soft-keys or the knob. Press the OK soft-key to initiate the selection and enter the sub-menu, or press the Back soft-key or the Home key to return to the home screen. 7.17.
8. Analogue Remote Control Two forms of voltage controlled remote operation are available: External Voltage Control, where an analogue voltage fully defines the demanded level of the chosen operating mode, and External TTL Control where an external logic voltage selects between the two levels set as Level A and Level B. The same rear panel control voltage input is used for both of these modes. These terminals are reference to chassis ground. Input impedance 10kΩ.
9. Application Notes This chapter is intended to give helpful information concerning practical applications of the unit. All electronic loads are subject to the impact of source characteristics, interconnection inductance and feedback loop characteristics, which can give rise to unexpected instability or poor dynamic behaviour. The information given here will assist in understanding the factors involved.
9.2 Stability of Source and Load Combinations This instrument is optimised for accuracy under constant load conditions by using a high gain feedback loop. Because of this, the possibility exists for combinations of source, interconnection and load characteristics to give rise to instability.
9.3.1 Source Characteristics The purpose of transient testing is to examine the behaviour of any feedback loops within the source. If the response of the source is under-damped, then in general the use of an active load will accentuate the effect. This is particularly true in the modes where the load responds to changes in voltage. At particular transient frequencies (particularly higher frequencies) the load may excite resonances in L-C filters or match the natural frequency of a feedback loop.
9.5.1 Constant Current Mode As described above, this is the fundamental operating mode of the power stages of this instrument, so it has the simplest feedback loop and the widest bandwidth. The sensed voltage signal is only used for the meters and protection. Constant current mode is normally used in conjunction with low impedance power supplies, and will be quite stable unless there is significant inductance in either the interconnections or the source.
9.5.3 Constant Conductance and Resistance Modes In both these modes, the analogue multiplier-divider is used to derive the current required from the sensed voltage. In Conductance mode the current required is calculated by multiplying the sensed voltage by the specified conductance; in Resistance mode the current required is calculated by dividing the difference between the sensed voltage and the dropout voltage setting by the specified resistance.
10. Remote Interface Configuration The LDH400P model can be remotely controlled via its RS232, USB, GPIB or LAN interfaces. The GPIB interface provides full facilities as described in IEEE Std. 488 parts 1 and 2. The RS232 interface communicates directly with a standard COM port. The USB interface enumerates as a Communications Class device and interacts with application software through a standard virtual COM port device driver on the PC.
10.3 USB Interface and Device Driver Installation The instrument firmware can be updated in the field through the USB port. This does not need the driver described here. It requires a PC software utility provided by the manufacturer, and uses a HID driver that will already be installed on the PC. If that is the only USB functionality required, download the package containing the firmware update together with the PC utility from the manufacturer, and follow the instructions included.
default configuration with DHCP enabled, so the unit will then follow the sequence described in the previous paragraph. Note that resetting the LAN interface removes any password protection.
included as part of the National Instruments Measurement and Automation Explorer package and the Keysight Vee application. 10.4.7 VXI-11 Discovery Protocol The instrument has very limited support of VXI-11 which is sufficient for the discovery protocol and no more. It implements a Sun RPC Port-mapper on TCP port 111 and UDP port 111 as defined in RFC1183. The calls supported are: NULL, GET PORT and DUMP.
11. Status Reporting The standard status and error reporting model described in IEEE Std. 488.2 was designed for the GPIB interface and contains some features intended for use with the Service Request and Parallel Poll hardware capabilities of that interface, and to accommodate its semi-duplex operation. Although those facilities are of little use with other interfaces, this instrument makes the full set of capabilities available to all of the interfaces.
that no longer apply will be cleared; any bit reporting a condition that remains true will remain set. The Input Trip Enable Register provides the mask between the Input Trip Register and the Status Byte Register. If any bit becomes ‘1’ in both registers, then the INTR bit (bit 1) will be set in the Status Byte Register. This enable register is set by the ITE command to a value 0 - 255, and read back by the ITE? query (which will always return the value last set by the controller).
The Standard Event Status Enable Register provides a mask between the Event Status Register and the Status Byte Register. If any bit becomes ‘1’ in both registers, then the ESB bit will be set in the Status Byte Register. This enable register is set by the *ESE command to a value 0 - 255, and read back by the *ESE? query (which will always return the value last set by the controller). On power-up it is set to 0. 11.
11.5 GPIB Parallel Poll (PRE) Complete Parallel Poll capabilities are offered by this instrument as defined in IEEE Std. 488.1. The Parallel Poll Enable Register (which is set by the *PRE command and read by the *PRE? query) specifies which bits in the Status Byte Register are to be used to form the ist local message. If any bit is ‘1’ in both the STB and the PRE then ist is ‘1’, otherwise it is ‘0’. The state of the ist message can also be read directly by the *IST? query.
11.8 LDH400P Status Model 11.
12. Remote Commands 12.1 Remote and Local Operation At power-on the instrument will be in the local state, with normal keyboard operation possible. All remote interfaces are active and listening for a remote command. When any command is received from any interface the instrument will enter the remote state. In this state the keyboard is locked out, the display switches to the home screen, with R E M O T E displayed in place of the soft-key tabs.
12.4 Command Timing There are no dependent parameters, coupled parameters, overlapping commands, expression program data elements or compound command program headers. Note, however, that the MODE command sets standard values for Level A, Level B, Range and the Slew Rate, so these must be explicitly set afterwards. Alternatively it is possible to use the store and recall facilities of the instrument to quickly retrieve a complete set-up of an operating mode and its values.
44 A? Return the set Level of Level A. The response is: A U where the is followed by a unit’s suffix determined by the load mode. B? Return the set Level of Level B. The response is: B U where the is followed by a unit’s suffix determined by the load mode. DROP Set the Dropout Voltage level to , in Volts. DROP? Returns the set Dropout Voltage level. The response is: DROP V where is in Volts.
12.6.2 Common Commands *IDN? Returns the instrument identification. The response is in the form , , , where is the manufacturer's name, is the instrument type, is the interface serial number and is the revision level of the firmware installed. *RST Resets the functional parameters of the instrument to the default settings as listed in the Factory Default Settings section. Does not affect the contents of the Save and Recall stores.
*PRE Set the Parallel Poll Enable Register to the value . *PRE? Report the value in the Parallel Poll Enable Register. The response is . *IST? Returns the state of the ist local message as defined by IEEE Std. 488.2. The response is 0 if the local message is false, or 1 if true. 12.6.4 Interface Management Commands LOCAL Go to local. Any subsequent command will restore the remote state.
13. Maintenance The Manufacturers or their agents overseas will provide a repair service for any unit developing a fault. Where owners wish to undertake their own maintenance work, this should only be done by skilled personnel in conjunction with the Service Guide, which may be obtained directly from the Manufacturers or their agents overseas. 13.1 Cleaning If the instrument requires cleaning use a cloth that is only lightly dampened with water or a mild detergent.
14. Sécurité Cet instrument est conforme à la classe de sécurité 1 de la classification CEI et il a été conçu pour satisfaire aux exigences de la norme EN61010-1 (Exigences de sécurité pour les équipements électriques de mesure, de contrôle et d'utilisation en laboratoire). Il s'agit d'un instrument de catégorie II d'installation prévu pour un fonctionnement à partir d’une alimentation monophasée standard.
15. Sicherheit Dieses Gerät wurde nach der Sicherheitsklasse (Schutzart) I der IEC-Klassifikation und gemäß den europäischen Vorschriften EN61010-1 (Sicherheitsvorschriften für elektrische Mess-, Steue-, Regel- und Laboranlagen) entwickelt. Es handelt sich um ein Gerät der Installationskategorie II, das für den Betrieb von einer normalen einphasigen Versorgung vorgesehen ist. Das Gerät wurde gemäß den Vorschriften EN61010-1 geprüft und in sicherem Zustand geliefert.
16. Sicurezza Questo strumento appartiene alla Categoria di Sicurezza 1 secondo la classifica IEC ed è stato progettato in modo da soddisfare i criteri EN61010-1 (requisiti di Sicurezza per Apparecchiature di misura, controllo e per uso in laboratorio). E’ uno strumento di Categoria II di installazione e inteso per funzionamento con un’alimentazione normale monofase. Questo strumento ha superato le prove previste da EN61010-1 e viene fornito in uno stato di sicurezza normale.
17. Seguridad Este es un instrumento de Clase Seguridad I según la clasificación del IEC y ha sido diseñado para cumplir con los requisitos del EN61010-1 (Requisitos de Seguridad para Equipos Eléctricos para la Medición, Control y Uso en Laboratorio). Es un equipo de Categoría de Instalación II que debe ser usado con suministro monofásico normal. Este instrumento se suministra habiendo sido comprobado según la norma EN61010-1.
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