10-10NoiseNoise varies with the carrier frequency. At high carrier frequencies, the noise is almost the same when themotor is operated with a commercial power supply. Motor noise, however, becomes louder when the motor isoperated at a speed higher than the rated speed (60 Hz). Using the Inverter for Special MotorsObserve the following precautions when using a special motor.Pole-changing MotorThe rated input current of pole-changing motors differs from that of standard motors. Select, therefore, anappropriate Inverter according to the maximum input current of the motor to be used. Before changing thenumber of poles, always make sure that the motor has stopped. Otherwise, the overvoltage protective or over-current protective mechanism will be actuated, resulting in an error.Submersible MotorThe rated input current of submersible motors is higher than that of standard motors. Therefore, always selectan Inverter by checking its rated output current. When the distance between the motor and Inverter is long, usea cable thick enough to connect the motor and Inverter to prevent motor torque reduction.Explosion-proof MotorWhen an explosion-proof motor is to be used, it must be subject to an explosion-proof test in conjunction withthe Inverter. This is also applicable when an existing explosion-proof motor is to be operated with the Inverter.Since the Inverter itself is, however, not explosion-proof, always install it in a safe place.GearmotorThe speed range for continuous operation differs according to the lubrication method and motor manufacturer.In particular, continuous operation of an oil-lubricated motor in the low speed range may result in burning. Ifthe motor is to be operated at a speed higher than 60 Hz, consult with the manufacturer.Synchronous MotorA synchronous motor is not suitable for Inverter control. If a group of synchronous motors is individuallyturned ON and OFF, synchronism may be lost.Single-phase MotorDo not use an Inverter for a single-phase motor. The motor should be replaced with a 3-phase motor. Power Transmission Mechanism (Speed Reducers, Belts, and Chains)If an oil-lubricated gearbox or speed reducer is used in the power transmission mechanism, oil lubrication willbe affected when the motor operates only in the low speed range. The power transmission mechanism willmake noise and experience problems with service life and durability if the motor is operated at a speed higherthan 60 Hz.
