Mitsubishi Elevator Power Circuit (PS) Troubleshooting Guide

1 Overview

The PS (Power Supply) circuit provides critical power to elevator subsystems, categorized into conventional power systems and emergency power systems.

Key Power Designations

Notes:

• Voltage levels may vary by elevator model (e.g., #79 in machine-room-less elevators matches #420 voltage).

• Always refer to model-specific technical manuals for exact specifications.

Conventional Power Systems

1. Transformer-Based:

   • Input: 380V AC → Output: Multiple AC/DC voltages via secondary windings.

   • Includes rectifiers for DC outputs (e.g., 5V for control boards).

   • Supplementary transformers may be added for high-capacity landing devices or safety lighting.

2. DC-DC Converter-Based:

   • Input: 380V AC → DC 48V → Inverted to required DC voltages.

   • Key Difference:

     • Imported systems retain AC power for landing/car top stations.

     • Domestic systems fully convert to DC.

Emergency Power Systems

• (M)ELD (Emergency Landing Device):

  • Activates during power outages to drive the elevator to the nearest floor.

  • Two types:

    1. Delayed Activation: Requires confirmation of grid failure; isolates grid power until operation completes.

    2. Instant Backup: Maintains DC bus voltage during outages.

Precharge/Discharge Circuits

• Function: Safely charge/discharge DC link capacitors.

• Components:

  • Precharge resistors (limit inrush current).

  • Discharge resistors (dissipate residual energy post-shutdown).

• Fault Handling: See MC Circuit section for regenerative system issues.

Precharge Circuit Schematic

2 General Troubleshooting Steps

2.1 Conventional Power System Faults

Common Issues:

1. Fuse/Circuit Breaker Tripping:

   • Steps:

     1. Disconnect the faulty circuit.

     2. Measure voltage at the power source.

     3. Check insulation resistance with a megohmmeter (>5MΩ).

     4. Reconnect loads one by one to identify the faulty component.

2. Abnormal Voltage:

   • Steps:

     1. Isolate the power source and measure output.

     2. For transformers: Adjust input taps if voltage deviates.

     3. For DC-DC converters: Replace the unit if voltage regulation fails.

3. EMI/Noise Interference:

   • Mitigation:

     • Separate high/low voltage cables.

     • Use orthogonal routing for parallel lines.

     • Ground cable trays to reduce radiation.

2.2 Precharge/Discharge Circuit Faults

Symptoms:

1. Abnormal Charging Voltage:

   • Check precharge resistors for overheating or blown thermal fuses.

   • Measure voltage drop across components (e.g., resistors, cables).

2. Extended Charging Time:

   • Inspect capacitors, balancing resistors, and discharge paths (e.g., rectifier modules, busbars).

Diagnostic Steps:

1. Disconnect all DCP (DC Positive) connections.

2. Measure precharge circuit output.

3. Reconnect DCP circuits incrementally to locate abnormal discharge paths.

2.3 (M)ELD System Faults

Common Issues:

1. (M)ELD Fails to Start:

   • Verify #79 power signal during grid failure.

   • Check battery voltage and connections.

   • Inspect all control switches (esp. in machine-room-less setups).

2. Abnormal (M)ELD Voltage:

   • Test battery health and charging circuits.

   • For systems with boost transformers: Verify input/output voltage taps.

3. Unexpected Shutdown:

   • Check safety relays (e.g., #89) and door zone signals.

3 Common Faults & Solutions

3.1 Voltage Abnormalities (C10/C20, H10/H20, S79/S420)

3.2 Control Board Failure to Power On

3.3 Transformer Damage

3.4 (M)ELD Malfunction

3.5 Precharge/Discharge Circuit Issues

Document Notes:
This guide aligns with Mitsubishi elevator standards. Always follow safety protocols and consult technical manuals for model-specific details.

© Elevator Maintenance Technical Documentation