M54125L データシートの表示（PDF） - MITSUBISHI ELECTRIC

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M54125L

EARTH LEAKAGE CURRENT DETECTOR

MITSUBISHI ELECTRIC  

MITSUBISHI <CONTROL / DRIVER IC>

M54125L/P

EARTH LEAKAGE CURRENT DETECTOR

LEAKAGE DETECTION FUNCTION

When leakage current current Ig appears on the primary side of

zero-current transformer, ZCT, leakage signal voltage VILK appears

on the secondary side and is input at ILK with bias VB as the

reference. In the half cycle when VILK is negative, capacitor CMM

connected to MM charges until VILK reaches the DC trip voltage.

If the voltage at MM does not reach the MM positive threshold

voltage, when the charging phase is completed, capacitor CMM

discharges at a small current. The output OUT is reset to the off

state (in which output current flows in) when VMM descends to the

MM negative threshold voltage.

Earth-leakage currents are detected when the amplitude of input

voltage VILK exceeds the DC trip voltage VLKT for longer than the

detection time tMM. The output OUT turns on for time tOUT. The

output current is used to turn on the thyristor that opens the

breaker contacts.

ABNORMAL VOLTAGE DETECTION FUNCTION

Normally VIBL, fixed amplitude AC supply that has been rectified

and divided by a resistor, is input to abnormal voltage input IBL.

When a fault occurs in the neutral line N, successive peaks of VIBL

become alternately small and large, with the levels determined by

the load on the AC power lines A and B.

When the amplitude of VIBL exceeds the abnormal voltage trip

voltage VBLT, capacitor CWF connected to pin WF discharges. After

the discharge shase is completed, charging begins again.) When

voltage VWF at WF drops below the WF threshold voltage,

capacitor CTD at TD charges, and after delay time tTD, when

voltage VTD at TD reaches the TD threshold voltage, output OUT

turns on, activating the circuit breaker. To avoid misoperation due

to the effect of repeated one-shot noise that brings VIBL above

VBLT, the voltage drops to the initial value only after time tWF.

This abnormal voltage detection circuit is enabled only when an

external resistor RX is connected to pin RX to enable the current

flow.

WAVEFORM DIAGRAM

1) Voltage waveform when earth leakage is detected.

ILK

VB

VB

VILK

MM 0

OUT 0

VMM

IMM

(3ms)

VLKT

MM positive direction threshold voltage

Note: Values in the parentheses are for reference only.

MM negative direction threshold voltage

tOUT(45ms)

2) Voltage waveform when abnormal voltage is detected.

VISL Noise

VBTL(3.9V)

IBL 0

VWF

WF threshold voltage

WF 0

TD 0

OUT 0

tWF(55ms)

VTD

tTD(300ms)

TD threshold voltage

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