True TBC-24-A, Руководство по обслуживанию

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47
15 & 24 INCH SERVICE MANUAL
VARIABLE SPEED COMPRESSOR DIAGNOSIS (SOME MODEL S)
The variable speed compressor is comprised of two components:
1.
The inverter board.
2.
The compressor.
The compressor speed board is supplied power from the AC line cord. This AC power is converted to DC power
on the board. The DC power is sequentially switched to the three motor windings to drive the compressor. By
adjusting the speed at which these three windings are switched the speed of the compressor can be adjusted.
The switching speed is determined by the amp draw of the compressor. As the load increases the amperage
of the compressor goes up the speed board speed up to compensate. As the amperage goes down the speed
board will slows the compressor down. The resulting speed will adjust between 4500 rpm and 1600 rpm.
PLE ASE NOTE: THE VA RIA BLE SPEED COMPRESSOR IS A 3 PHASE DC COMPRESSOR APPLYING LINE
VOLTAGE TO COMPRESSOR WILL DAMAGE IT.
The VCC looks very similar to a standard single speed compressor. The three terminals on the side of the
compressor look the same also. However when taking resistance measurements around the terminals to the
outside of the case do not let the different motor design cause confusion. The first check is still to verify that
there is NO continuity to the case itself. This is the same as with any standard compressor. When checking
between the three terminals, the resistance measurements should be equal regardless of which two terminals
you are checking. There are three identical windings attached to these terminals so the resistance of the
windings should be equal. It should never read 0 or infinity ohms. With the compressor at 77º the windings will
read about 16 ohms each (see example A).
16Ω
16Ω
16Ω
150 VAC.
150 V
AC.
150 V
AC.
Example A Example B