1.3 Precautions for Using Inverters
1-11
1.3.4 Noise reduction
If noise generated from the inverter affects other devices, or that generated from peripheral equipment causes the
inverter to malfunction, follow the basic measures outlined below.
(1) If noise generated from the inverter affects the other devices through power wires or grounding wires:
- Isolate the grounding terminals of the inverter from those of the other devices.
- Connect a noise filter to the inverter power wires.
- Isolate the power system of the other devices from that of the inverter with an insulated transformer.
- Decrease the inverter's carrier frequency (F26). See Note below.
(2) If induction or radiated noise generated from the inverter affects other devices:
- Isolate the main circuit wires from the control circuit wires and other devices wires.
- Put the main circuit wires through a metal conduit pipe, and connect the pipe to the ground near the inverter.
- Install the inverter into the metal panel and connect the whole panel to the ground.
- Connect a noise filter to the inverter power wires.
- Decrease the inverter's carrier frequency (F26). See Note below.
(3) When implementing measures against noise generated from peripheral equipment:
- For inverter's control signal wires, use twisted or shielded-twisted wires.
When using shielded-twisted wires, connect the shield of the shielded wires to the common terminals of
the control circuit.
- Connect a surge absorber in parallel with magnetic contactor's coils or other solenoids (if any).
Note: Running a permanent magnet synchronous motor (PMSM) at a low carrier frequency may heat the permanent
magnet due to the output current harmonics, resulting in demagnetization. When decreasing the carrier
frequency setting, be sure to check the allowable carrier frequency of the motor.
1.3.5 Leakage current
A high frequency current component generated by insulated gate bipolar transistors (IGBTs) switching on/off inside
the inverter produces leakage current through stray capacitance of inverter input and output wires or a motor. If any
of the problems listed below occurs, take an appropriate measure against them.
An earth leakage circuit breaker* that is
connected to the input (primary) side has
tripped.
* With overcurrent protection
1) Decrease the carrier frequency. See Note below.
2) Make the wires between the inverter and motor as short as
possible.
3) Use an earth leakage circuit breaker with lower sensitivity than
the one currently used.
4) Use an earth leakage circuit breaker that features measures
against the high frequency current component (Fuji SG and EG
series).
An external thermal relay was falsely
activated.
1) Decrease the carrier frequency. See Note below.
2) Increase the current setting of the thermal relay.
3) Use the electronic thermal overload protection built in the
inverter, instead of the external thermal relay.
Note: Running a permanent magnet synchronous motor (PMSM) at a low carrier frequency may heat the permanent
magnet due to the output current harmonics, resulting in demagnetization. When decreasing the carrier
frequency setting, be sure to check the allowable carrier frequency of the motor.
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