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-18
Do Not Use an Electromagnetic Switch
Never connect an electromagnetic switch (MC) between the Inverter and motor and turn it ON or OFF during
operation. If the MC is turned ON while the Inverter is operating, a large inrush current will be caused and the
overcurrent protection in the Inverter will operate.
When using an MC to switch to a commercial power supply, stop the Inverter and motor before operating the
MC. Use the speed search function if the MC is operated during operation. If measures for momentary power
interrupts are required, use a delayed release MC.
Installing a Thermal Overload Relay
This Inverter has an electronic thermal protection function to protect the motor from overheating. If, however,
more than one motor is operated with one Inverter or a multi-polar motor is used, always install a thermal
relay (THR) between the Inverter and the motor and set L1-01 to 0 (no motor protection). The sequence
should be designed so that the contacts of the thermal overload relay turn OFF the magnetic contactor on the
main circuit inputs.
Installing a Noise Filter on Output Side
Connect a noise filter to the output side of the Inverter to reduce radio noise and inductive noise.
Fig 2.9 Installing a noise filter on the output side
Countermeasures against Inductive Noise
As described previously, a noise filter can be used to prevent inductive noise from being generated on the out-
put side. Alternatively, cables can be routed through a grounded metal pipe to prevent inductive noise. Keep-
ing the metal pipe at least 30 cm away from the signal line considerably reduces inductive noise.
Fig 2.10 Countermeasures against Inductive noise
Inductive noise: Electromagnetic induction generates noise on the signal line, causing the controller to malfunction.
Radio noise: Electromagnetic waves from the Inverter and cables cause the broadcasting radio receiver to make noise.
Signal line
Powersupply
3G3PV
3G3IV-PLF
Inverter
AM radio
Controller
Noise
Filter
Radio noise
Inductive noise
Controller
30cm min.
Signal line
Inverter
Power supply
Metal pipe
3G3PV
