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MELSEC-Q Series

Insulation monitoring

Insulation monitoring module measuring leakage current

●Insulation monitoring module QE82LG

Leakage current can be measured for safety measures. Risks of electric shock are detected by monitoring leakage current (Io).
The isolated state of equipment can be constantly monitored.
The resistive leakage current (Ior) is measured to constantly monitor the deterioration of equipment insulation.
Two-stage warning is provided for each measurement item. Two-stage warning for each of leakage current (Io) and resistive leakage current (Ior) can be issued via program-less communication. The two-stage warning function can be used to give a warning for calling for attention and a hazard warning.
One module can monitor two circuits. One module can monitor two circuits of power supplies of the same phase/wire type on the same system.
In addition, the parameters can be set easily with GX Works2 (Version 1.91V and higher).

Measurement items
Leakage current (Io) and resistive leakage current (Ior)

Model QE82LG
Phase/wire type Common to single-phase 2-wire and single-phase 3-wire/three-phase 3-wire types
Instrument rating Voltage circuit*1 *2 Single-phase 2-wire
Three-phase 3-wire
Common to 110 V AC and 220 V AC
Single-phase 3-wire 110 V AC (between wires 1 and 2, between wires 2 and 3), 220 V AC (between wires 1 and 3)
Leakage current circuit 1 A AC (ZCT is used. Primary current of ZCT)
Frequency 50/60 Hz (automatic discrimination of frequency)
Number of circuits which can be monitored 2 circuit*3

*1: The module can be connected directly to 110-V and 220-V power supplies. To connect to a 440-V power supply, an external voltage transformer (VT) is necessary. Leakage current cannot be measured if voltage input is not provided.

*2: Resistive leakage current (Ior) can be measured on single-phase 3-wire and three-phase 3-wire delta circuits. On special circuits, such as three-phase 3-wire star circuits, highresistance grounding circuits and capacitor grounding circuits, only Io can be measured.

*3: Leakage current (Io, Ior) measurement on CH1 and CH2 can be performed only on circuits on the same system as the voltage input.

Early detection of insulation deterioration of production equipment

  • The structure directly connected to programmable controller in the control panel saves space and facilitates measurement of leakage current in places close to loads.
  • Failures caused by leakage (earth fault) and insulation of motor loads in production equipment can be monitored. Progression of insulation deterioration is not overlooked.
  • The upper limit warning monitor can be set in two stages. Insulation deterioration and condition can be observed at an early stage, so that preventive measures can be taken before production equipment suddenly stops or goes down.

Early detection of insulation deterioration of production equipment

Ior method realizes constant monitoring of insulation deterioration of equipment

  • With the conventional systems, such as inverter circuits with large capacitive leakage current (loc), it has difficulty for insulation monitoring.
    The module is capable of measuring resistive leakage current (lor), and removes the capacitive leakage current then monitors the accurate leakage current caused by insulation deterioration.
  • Resistive leakage current (Ior) is constantly measured even during operation of equipment. Signs of insulation deterioration can be detected without power interruption.

Leakage current (Io) is affected by capacitive leakage current (Ioc) of entire equipment.
Therefore, resistive leakage current (Ior) measurement is effective in diagnosis of insulation deterioration.

Method of measuring leakage current (Io measurement and Ior measurement)
Method of measuring leakage current (Io measurement and Ior measurement)

  • Capacitive leakage current (Ioc) fluctuates in equipment with long wiring or equipment with inverter devices and filters

Capacitive leakage current (Ioc) fluctuates in equipment with long wiring or equipment with inverter devices and filters

Lineup

Energy measuring Insulation monitoring
2 QE82LG