Chapter 2 Installation and Wiring
16
output cables and the control signal cables greater than 30 cm, the effect of conduction
interference will obviously decrease too.
Countermeasures to RFI: The input cables, output cables and the inverter itself would
produce RFI. Placing noise filters both at input and output sides, and shielded with metal
shell would reduce RFI.. The cables between the inverter and the motor should be as
short as possible. Measure to reduce RFI is shown as Figure 2-10.
Power
supply
Noise
Filter
Inverter
Noise
Filter
Motor
Metal tube
Metal shell box
Fig. 2-10 Method to Restrain RFI
Distance between the inverter and the motor.
The longer the distance between the inverter and the motor, the higher the carrier
frequency would be, and the greater the high harmonic leakage current of the cables
would be. Leakage current has a negative impact to inverters and equipments nearby, so
reduce leakage current as little as possible.
The relationship of the distance between the inverter and the motor and carrier frequency
is shown as Table 2-7.
Table 2-7 Distance between the inverter and the motor and carrier frequency.
Distance between inverter
and motor
Below 50m Below 100m Above 100m
Carrier frequency Below 8 kHz Below 4 kHz Below 2 kHz
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