Fisher & Paykel 635 Active Smart Service Manual page 46

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Step 3 – Check the input frequency of the inverter.
• Switch the multi-meter to the frequency range (if it has one). The frequency input into the Inverter from
the power controller can be measured.
• There are two terminals alongside the edge connector that this measurement can be taken from in the
inverter. How fast the compressor is running will depend on how cold the PC & FC are. Depending on
the compressor and the speed it is running at at the time the reading is taken, the frequency will vary
between about 53Hz and 177 Hz.
• If unable to obtain a frequency reading from the power controller to the inverter, suspect the fault to be in
the power controller.
Meter switched to
Frequency Range (Hz)
Output Voltage
The measurement of an output voltage using a multimeter/voltmeter will not give a valid reading in a no load state,
because once the inverter is unable to "sense" the motor inductance on its output it will cease to operate.
The best method would be to use a current probe connected to an oscilloscope and measure one of the
output phases (blue, black or brown wires) from the inverter, while the inverter is still connected to the
compressor.
While it is appreciated that oscilloscopes and current probes are not commonly available to service
technicians, it is not a valid test to even try to measure the output voltage, and that is one of the reasons why
we have introduced this type of inverter with the built-in LED diagnostic feature.
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