Precautions In Running Inverters; Precautions In Using Special Motors - Fuji Electric FRENIC-HVAC User Manual

2.8.2

Precautions in running inverters

Precautions for running inverters to drive motors or motor-driven machinery are described below.
 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.
 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 the carrier frequency of the inverter.
Operation at 60 Hz or higher can also result in higher noise level.
 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. If it happens, do any of the following:
- 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 6 "FUNCTION CODES."
2.8.3

Precautions in using special motors

When using special motors, note the followings.
 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.
 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.
 Geared motors
If the power transmission mechanism uses an oil-lubricated gearbox or speed changer/reducer, then
continuous operation at low speed may cause poor lubrication. Avoid such operation.
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