E6582062
10-9 10. Selection and installation of peripheral devices
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10. 2. 4 Installation of a thermal relay (THR)
Use an electronic thermal protector of the inverter for motor overload protection. Set a motor overload pro-
tection level with a parameter according to the motor rating.
However, in the following cases, install a thermal relay (THR) between the inverter and motor (secondary
side).
• Running multiple motors simultaneously with one inverter.
In this case, install a thermal relay on each motor.
• Running a motor with smaller output than applicable motor output of the standard specification
(When the motor capacity is too small to set with a parameter of the motor overload protection level).
For details on motor overload protection level, refer to [5. 3. 5].
To give sufficient protection for the motor running in a low-speed range, the use of a motor with motor
winding embedded type thermal relay is recommended.
Important
• Be sure to have interlock for the commercial power supply is applied to the inverter output
terminal.
• Do not turn the magnetic contactor (MC) in the secondary circuit ON/OFF during run. It can
cause failure due to rush current flowing to the inverter.
• Install a surge absorber on the exciting coil of a magnetic contactor (MC).
Important
• "Thermal overload relay" is recommended, install it for each motor to be protected. "Thermal
relay with CT" is not available.
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