1.6 Precautions for Using Inverters
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Chapter 1 BEFORE USE
1.6.4 Precautions in running inverters
Precautions for running inverters to drive motors or motor-driven machinery are described below.
îš„ Motor temperature
When an inverter is used to run a general-purpose motor, the motor temperature becomes higher than
when it is operated with a commercial power supply. In the low-speed range, the motor cooling effect will
be weakened, so decrease the output torque of the motor when running the inverter in the low-speed
range.
îš„ Motor noise
When a general-purpose motor is driven by an inverter, the noise level is higher than that when it is driven
by a commercial power supply. To reduce noise, raise carrier frequency of the inverter. Operation at 60 Hz
or higher can also result in a higher noise level.
îš„ Machine vibration
When an inverter-driven motor is mounted to a machine, resonance may be caused by the natural
frequencies of the motor-driven machinery. Driving a 2-pole motor at 60 Hz or higher may cause abnormal
vibration.
• Consider the use of a rubber coupling or vibration-proof rubber.
• Use the inverter's jump frequency control feature to skip the resonance frequency zone(s).
• Use the vibration suppression related function codes that may be effective. For details, refer to the
description of H80 in Chapter 5 "FUNCTION CODES."
1.6.5 Precautions in using special motors
When using special motors, note the followings.
îš„ Explosion-proof motors
When driving an explosion-proof motor with an inverter, use a combination of a motor and an inverter that
has been approved in advance.
îš„ Submersible motors and pumps
These motors have a larger rated current than general-purpose motors. Select an inverter whose rated
output current is greater than that of the motor. These motors differ from general-purpose motors in
thermal characteristics. Decrease the thermal time constant of the electronic thermal overload protection to
match the motor rating.
îš„ Brake motors
For motors equipped with parallel-connected brakes, their power supply for braking must be supplied from
the inverter input (primary) circuit. If the power supply for braking is mistakenly connected to the inverter's
output (secondary) circuit, the brake may not work when the inverter output is shut down. Do not use
inverters for driving motors equipped with series-connected brakes.
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