YASKAWA Varispeed F7 Instruction Manual page 53

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.
Inductive Noise:
Radio Noise:
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.
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2
Power
MCCB
supply
Inverter
Electromagnetic induction generates noise on the signal line, causing the controller to malfunction.
Electromagnetic waves from the Inverter and cables cause the broadcasting radio receiver to make
noise.
Fig 2.9 Installing a Noise Filter on the Output Side
Power
MCCB
supply
Fig 2.10 Countermeasures Against Inductive Noise
Noise
IM
filter
Radio noise
AM radio
Inductive
noise
Signal line
Controller
Metal pipe
Inverter
IM
30 cm min.
Signal line
Controller