Mitsubishi Electronics FR-S500 Line-to-line leakage currents, Install one NFB per inverter

					Main circuit terminals
(2) Line-to-line leakage currents
Harmonics of		NFB		Thermal relay
leakage currents						Motor
flowing in static	Power		Inverter			IM
capacities between	supply
the inverter output
					Line static
cables may operate					capacitances
the external thermal		Line-to-Line Leakage Current Path
relay unnecessarily.

Countermeasures

•Use the electronic thermal relay function of the inverter.

•Decrease the carrier frequency. Note that motor noise increases. Selection of Soft-PWM (Pr. 70) makes it unoffending.

To ensure that the motor is protected against line-to-line leakage currents, it is recommended to use a temperature sensor to directly detect motor temperature.

Installation and selection of no-fuse breaker

Install a no-fuse breaker (NFB) on the power receiving side to protect the wiring of the inverter primary side. Select the NFB according to the power supply side power factor (which depends on the power supply voltage, output frequency and load). Especially for a completely electromagnetic NFB, one of a slightly large capacity must be selected since its operation characteristic varies with harmonic currents. (Check it in the data of the corresponding breaker.) As an ground leakage breaker, use the Mitsubishi ground leakage breaker designed for harmonics and surge suppression. (Refer to page 10 for the recommended models.)

CAUTION

•Select the NFB according to the inverter power supply capacity.

•Install one NFB per inverter.

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WIRING

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