Mitsubishi Electric FR-A800, Instruction Manual

Page: 474 / 1042

(H) Protective function parameter Parameters
5 - 294
NOTES The internal accumulated heat value of the electronic thermal relay function is reset to the initial
value by the inverter's power reset and reset signal input. Avoid unnecessary reset and power-
OFF.
Install an external thermal relay (OCR) between the inverter and motors to operate several motors,
a multi-pole motor or a dedicated motor with one inverter. When setting an external thermal
relay, note that the current indicated on the motor rating plate is affected by the line-to-line leak-
age current. (Refer to page 3-1.) The cooling effect of the motor drops during low-speed opera-
tion. Use a thermal protector or a motor with built-in thermistor.
The protective characteristic of the electronic thermal O/L relay is degraded when there is a large
difference in capacity between the inverter and motor, and when the set value is small. In such
case, use an external thermal relay.
A dedicated motor cannot be protected by an electronic thermal O/L relay. Use an external ther-
mal relay.
Set Pr. 9 = "0" for vector-control-dedicated motors (SF-V5RU) because they are equipped with
thermal protectors.
The transistor protection thermal O/L relay is activated early when the Pr. 72 "PWM frequency
selection" is increased.