10
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Inverter Application Precautions
This section provides precautions for selecting, installing, setting, and handling Inverters.
Selection
Observe the following precautions in selecting an Inverter.
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 phase advancing capacitor. Excessive peak cur-
rent can destroy the convertor section. To prevent this, install a DC or AC reactor (optional) to improve the
power supply power factor.
DC reactors are built into 200 V Class Inverters of 22 to 110 kW and 400 V Class Inverters of 22 to 300 kW.
If a thyristor convertor, 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.
Fig 10.5
Inverter Capacity
When connecting special motors or multiple motors in parallel to an Inverter, select the Inverter capacity so
that the rated output current of the Inverter is 1.1 times the sum of all the motor rated currents.
Applications with Repetitive Loads
Applications with repetitive loads (cranes, elevators, presses, washing machines, etc.) using Inverters require
derating for the repetitive load [reducing carrier frequency and current (changing accel/decel timing, increas-
ing the frame size of the Inverter)]. Contact your Yaskawa representative for details.
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 characteristics are generally less than those required when start-
ing using a normal commercial power supply. If a large initial torque is required, select an Inverter with a
somewhat larger capacity or increase the capacity of both the motor and the Inverter.
Emergency Stop
Although the Inverter's protective functions will stop operation when a fault occurs, the motor will not stop
immediately. Always provide mechanical stop and protection mechanisms on equipment requiring an emer-
gency stop.
Power supply
capacity (kVA)
DC or AC reactor
Required
DC or AC reactor
Not required
Inverter capacity (kVA)
