Toshiba TOSVERT VF-A7 Instruction Manual page 26

Power
supply
Measures to be taken:
1. Use the electronic thermal function provided for the inverter.
Use parameter , to set the electronic thermal function.
2. Lower the PWM carrier frequency, though this results in an increase in motor magnetic noise.
Use parameter  to lower the PWM carrier frequency.
3. For improvement, connect film capacitors with capacitance of 0.1 to 0.5 F-1000V to the
input and output terminals in each phase of the each thermal relay.
CT and ammeter
When a CT and an ammeter are installed externally to monitor the output current of the
inverter, the ammeter could be burned by the high-frequency elements of a leakage current.
For a model with relatively long cables (longer than 50 m) or a model for motors with small
current ratings (several amperes), especially 400V model with a small capacity (3.7kW or less),
the ammeter can be burned more easily by the high-frequency elements of a leakage current
which flows into it through the external CT because a leakage current can be too large as
compared with the current rating of the motor.
Measures to be taken:
1. For external meters, use the meter output terminals in the inverter's control circuit.
Output currents can also be output to the meter output terminals (AM). Use a 1 mAdc full-
scale ammeter or a 7.5 Vdc-1 mA full-scale voltmeter.
2. Use the monitor function provided for the inverter.
Use the monitor function provided for the inverter to check the output current.
Inverter
U/T1
V/T2
W/T3
A-13
A
IM
IM