1-7
Leakage current
A high frequency current component generated by insulated gate bipolar transistors (IGBTs) switching on/off inside the
inverter becomes leakage current through stray capacitance of inverter input and output wires or a motor. If any of the
problems listed below occurs, take an appropriate measure against them.
Problem Measures
An earth leakage circuit
breaker* that is connected
to the input (primary) side
has tripped.
*With overcurrent protection
1) Decrease the carrier frequency.
2) Make the wires between the inverter and motor shorter.
3) Use an earth leakage circuit breaker with lower sensitivity than the one currently used.
4) Use an earth leakage circuit breaker that features measures against the high frequency
current component (Fuji SG and EG series).
An external thermal relay
was activated.
1) Decrease the carrier frequency.
2) Increase the current setting of the thermal relay.
3) Use the electronic thermal overload protection built in the inverter, instead of the
external thermal relay.
Selecting inverter capacity
(1) To drive a general-purpose motor, select an inverter according to the nominal applied motor rating listed in the standard
specifications table. When high starting torque is required or quick acceleration or deceleration is required, select an
inverter with one rank higher capacity than the standard.
(2) Special motors may have larger rated current than general-purpose ones. In such a case, select an inverter that meets the
following condition.
Inverter rated current > Motor rated current
1.3.2 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 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 5 "FUNCTION CODES."
To Next Page
Loading...
