Specifications

98
■ Pole Change
Motors
■ Submersible
Motors
■ Explosion-proof
Motors
■ Geared Motors
■ Synchronous
Motors
■ Single-phase
Motors
■Uras Vibrators
■
Motors with Brakes
Select the inverter with a capacity exceeding the rated current of each pole. Pole change should be
made after the motor stops. If a pole is changed while the motor is rotating, the regenerative
overvoltage or overcurrent protection circuit is activated and the motor then coasts to a stop.
Since the rated current of underwater motors is large compared with general purpose motors,
select an inverter with a larger capacity. If the distance between the inverter and the motor is great,
use cables with sufficiently large diameters.
Explosion-proof motors which are applied to an inverter, must be currently rated and approved as
explosion-proof equipment. The inverter and pulse coupler (pulse signal repeater) are not
explosion-proof and should not
be located where explosive gases exist. The PG attached to flame-
proof type inverter is safety explosion-proof type. Be sure to connect an exclusive pulse coupler
when wiring between the PG and inverter.
Lubrication method and continuous rotation limit differ with manufacturers. When oil lubrication is
employed, continuous operation in low speed range may cause burnout. Before operating the
motor at more than 60 Hz you should consult the motor manufacturer.
Synchronous motor is not suitable for inverter control. If a group of synchronous motor is
individually turned ON and OFF, synchronism may be lost.
Single-phase motors are not suitable for variable speed operation with an inverter. If the inverter is
applied to a motor using a capacitor stack, a high harmonic current flows and the capacitor may be
damaged. For split-phase start motors and repulsion start motors, the internal centrifugal switch
will not be actuated and the starting coil may burn out. Therefore, use only 3-phase motors.
Uras vibrator is a vibration motor which gets power from centrifugal force by rotating unbalance
weights on both ends of the shaft. When driving by inverter, select inverter capacity considering
followings. For details, contact your YASKAWA representative.
（1）Uras vibrator should be used at inverter rated frequency or less.
（2）V/f control should be used.
（3）Set acceleration time 5 to 15 because load inertia of uras vibrator is 10 to 20 times of motor
inertia.
Note: When the acceleration time is less than 5 s, select inverter capacity.
Contact your YASKAWA representative for details.
（4）Inverter might not start due to undertorque because eccentric moment torque (static friction
torque at start) is too large.
Use brake-equipped motors with an independent power supply. Connect the brake power supply to
the inverter primary side. When the brake operates (motor stops) it turns the inverter output OFF.
Some types of brakes may make abnormal sounds in low speed range.
Application to Special Purpose Motors