Appendix A Trouble-free Use of Inverters (Notes on electrical noise)
Excerpt from technical material of
the Japan Electrical Manufacturers’ Association (JEMA) (April 1994)
A.1 Effect of inverters on other devices
Inverters have been and are rapidly expanding its application fields. This paper describes the effect that inverters
have on electronic devices already installed or on devices installed in the same system as inverters, as well as
introducing noise prevention measures. (Refer to “A.3 [ 3 ] Noise prevention examples“ for details.)
[ 1 ] Effect on AM radios
Phenomena If an inverter operates, AM radios may pick up noise radiated from the inverter. (An
inverter has almost no effect on FM radios or television sets.)
Probable cause The noise radiated from the inverter may be received by a radio.
Measure Inserting a noise filter on the power supply side of the inverter is effective.
[ 2 ] Effect on telephones
Phenomena If an inverter operates, nearby telephones may pick up noise radiated from the
inverter in conversation so that it may be difficult to hear.
Probable cause A high-frequency leakage current radiated from the inverter and motors enters
shielded telephone cables, causing noise.
Measure It is effective to commonly connect the grounding terminals of the motors and return
the common grounding line to the grounding terminal of the inverter.
[ 3 ] Effect on proximity switches
Phenomena If an inverter operates, proximity switches (capacitance-type) may malfunction.
Probable cause The capacitance-type proximity switches may provide inferior noise immunity.
Measure It is effective to connect a filter to the input terminals of the inverter or change the
power supply treatment of the proximity switches. The proximity switches can be
replaced with superior noise immunity types such as magnetic types.
[ 4 ] Effect on pressure sensors
Phenomena If an inverter operates, pressure sensors may malfunction.
Probable cause Noise may penetrate through a grounding wire into the signal line.
Measure It is effective to install a noise filter on the power supply side of the inverter or to
change the wiring.
[ 5 ] Effect on position detectors (pulse encoders)
Phenomena If an inverter operates, pulse encoders may produce erroneous pulses that shift the
stop position of a machine.
Probable cause Erroneous pulses are liable to occur when the signal lines of the PG and power lines
are bundled together.
Measure The influence of induction noise and radiated noise can be reduced by separating
the PG signal lines and power lines. Providing noise filters at the input and output
terminals is also an effective measure.
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