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2. Installation and wiring 2-70
2
9
â– Influence of leakage current across lines (in case of CT and ammeter)
If a CT and ammeter are connected externally to detect inverter output current, the leak current's
high frequency component may destroy the ammeter. If the wires are long (50 m or more) or in case
of models with motors of low rated current (several A (ampere) or less), especially the 480 V class
low capacity (4.0 kW or less, 5.5 kW or less with ND) models, it will be easy for the high frequency
component to pass through the externally connected CT and be superimposed on and burn the
ammeter, because the ratio of leakage current against the motor's rated current will increase.
Here are some examples of measures against leakage current across lines.
• Connect the ammeter to the terminal [FM] and terminal [AM] of the inverter.
For how to connect the meter and how to set parameters, refer to [5. 3. 6].
• Check the current value with the monitor function.
For details, refer to [8. 1. 1].
• Set <F300: Carrier frequency> to 5 kHz or less.
However, this may increase noise on the motor side.
For details, refer to [6. 14].
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