Fuji Electric FRENIC-MEGA, Instruction Manual

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1-9
Chap. 1
BEFORE U
S
IN
G
THE IN
VE
R
T
ER
1.3.2 Precautions in running inverters
Precautions for running inverters to drive motors or motor-driven machinery are described below.
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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.
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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 higher noise level.
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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 5 "FUNCTION CODES."
1.3.3 Precautions in using special motors
When using special motors, note the followings.
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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.
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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.
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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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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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Synchronous motors
It is necessary to take special measures suitable for this motor type. Contact your Fuji Electric representative for details.
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Single-phase motors
Single-phase motors are not suitable for inverter-driven variable speed operation.
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High-speed motors
If the reference frequency is set to 120 Hz or higher to drive a high-speed motor, test-run the combination of the inverter and
motor beforehand to check it for the safe operation.