10-2
10
Inverter Application Precautions
îš‹ Selection
Observe the following precautions when selecting an Inverter.
îš„Installing Reactors
A large peak current will flow in the power input circuit when the Inverter is connected to a large-capacity
power transformer (600 kVA or higher) or when switching a compensating capacitor. Excessive peak current
can destroy the rectifier section. To prevent this, install a DC or AC reactor to improve the power supply
power factor.
DC reactors are built into Inverters of 22kW and more.
If a thyristor converter, such as a DC drive, is connected in the same power supply system, connect a DC or
AC reactor regardless of the power supply conditions shown in the following diagram.
îš„Inverter Capacity in Multiple Motors Applications
When connecting multiple motors in parallel to an Inverter, select the Inverter capacity so that the rated output
current of the Inverter is minimum 1.1 times the sum of all the motor rated currents.
îš„Initial Torque
The startup and acceleration characteristics of the motor are restricted by the overload current ratings of the
Inverter that is driving the motor. The torque characteristic generally is different from those when starting a
motor on the power supply directly. If a large initial torque is required, select an Inverter one size bigger or
increase the capacity of both, the motor and the Inverter.
Power supply
(kVA)
DC or AC reactor re-
quired
DC or AC reactor not re-
quired
Inverter capacity (kVA)
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