Toshiba VF-A7 1.4.2 Notes on inverters, Note on the disposal of inverters

A-11
1.4.2 Notes on inverters
Over-current protective function
The inverter has an over-current protective function. The current for this protection is adjusted
to the maximum current rating of the applicable motors by default. Therefore, when the
inverter is used to control a motor with a relativel y small capacity, it is necessary to readjust the
over-current protection level and the electronic thermal protecti ve function. In such a case,
follow the procedure specified in 5.13 to readjust them.
Inverter capacity
An inverter with a small capacity (kVA) must not be used for a motor with a relatively large
capacity even if the motor is operated under a small lo ad. If an inverter is used this way, the
output peak current rises high because of a current ripple, thus causing the m otor to trip easily.
Power factor improving capacitor
No power factor improving capacitor should be connected on the output side of the inverter.
When the inverter is used for a motor equipped with a capacitor for power fac tor improvement,
remove the capacitor from the motor. Connecting such a capacitor causes the inverter to break
down and the motor to trip, or breaks the capacitor itself.
Use of an inverter at a voltage other than the rated one
There is a need to connect it to a power unit supplying a voltage differ ent from the rated
voltage, increase or reduce the supply voltage to the inverter's rated voltage, us ing a
transformer, etc.
Use of a set of inverters, which requires circuit-breaking devices
Circuit-breaking of defective inverter
When two or more inverters are connected to the same power line as shown above, it is
necessary to select a circuit-breaking characteristic ensuring th at, for example, if a short circuit
occurs in INV 1, on ly MCCB2 trips but not MC CB1. If it is difficult to select a proper characteristic,
then insert a breaking fuse between MCCB2 and INV 1 in this case.
Note on the disposal of inverters
Be sure to dispose of inverters as industrial wastes, when they becom e unnecessary.
Remove the power factor improving
capacitor and the surge absorber, if any.
Power factor improving capacitor
U
V
W
Inverter IM
Breaking fuse)