Toshiba VF-A7 instruction manual Power supply

Power supply

Inverter

IM

A

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 0.5μF-1000V to the input and output terminals in each phase of the each thermal relay.

U/T1

V/T2

W/T3

IM

②CT 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.

A-13