Specifications
95
Application of Peripheral Unit
■ Installing a Ground
Fault Interruptor or an
MCCB
■ Use of Power Supply
Side Magnetic
Contactor
■ Use of Motor Side
Magnetic Contactor
■ Motor Thermal Over
Load Relay Installation
Be sure to install an MCCB or an ELCB that is recommended by Yaskawa at the power
supply side of the drive to protect internal circuitry.
The type of MCCB is selected depending on the power supply power factor (power supply
voltage, output frequency, load characteristics, etc.). Sometimes a fairly large MCCB may be
required due to the affects of harmonic current on operating characteristics. If you do not
use a recommended ELCB, use one fitted for harmonic suppression measures and designed
specifically for drives. A malfunction may occur due to high-frequency leakage current, so
the rated current of the ELCB must be 30 mA or higher per drive unit. If a malfunction
occurs in an ELCB without any countermeasures, reduce the carrier frequency of the drive,
replace the ELCB with one that has countermeasures against high frequency, or use an
ELCB which has a rated current of 200 mA or higher per drive unit.
Select an MCCB or an ELCB with a rated capacity greater than the short-circuit current for
the power supply. For a fairly large power supply transformer, a fuse can be added to the
ELCB or MCCB in order to handle the short-circuit current level.
Use a magnetic contactor (MC) to ensure that power to the drive can be completely shut off
when necessary. The MC should be wired so that it opens when a fault output terminal is
triggered. Even though an MC is designed to switch following a momentary power loss,
frequent MC use can damage other components. Avoid switching the MC more than once
every 30 minutes. The MC will not be activated after a momentary power loss if using the
operator keypad to run the drive. This is because the drive is unable to restart automatically
when set for LOCAL.
Although the drive can be stopped by using an MC installed on the power supply side, the
drive cannot stop the motor in a controlled fashion, and it will simply coast to stop. If a
braking resistor or dynamic braking unit has been installed, be sure to set up a sequence
that opens the MC with a thermal protector switch connected to the braking resistor device.
In general magnetic contactors on the output of the inverter, for motor control should not be
used. Starting a motor with the inverter running will cause large surge currents and the
inverter overcurrent protector to trigger. If an MC is used for switching to commercial
power supply, switch MC after the inverter and the motor stop. To switch during motor
rotation, use the speed search function. (See P40.)
Although the drive comes with built in electrothermal protection to prevent damage from
overheat, a thermal relay should be connected between the drive and each motor if running
several motors from the same drive. For a multipole motor or some other type of non-standard
motor, Yaskawa recommends using an external thermal relay appropriate for the motor. Be
sure to disable the motor protection selection parameter (L1-01 = 0), and set the thermal relay
or thermal protection value to 1.1 times the motor rated current listed on the motor nameplate.
Notes