7.OPERATING PRINCIPLE OF MAJOR COMPONENTS, AND INSPECTION METHOD
7-1.Compressor Motor
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| Inspection method |
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| The compressor motor, mounted directly to the | 1) Measure | the | resistance | of each winding of | the | |||||
| compressor and located inside a sealed steel | compressor. |
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| case, has two windings. | a. Disconnect the power cord. |
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| One is a start winding and the other a run winding. | b. Remove the relay from the compressor. |
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| The windings are connected together internally, | C. Measure the resistance of each winding. |
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| forming a common connection. A lead is connected | A. The highest resistance value is the measurement of | |||||||||
| to each of the | windings, and to the common | |||||||||
| connection. These three leads are then connected | the "start" and | "run" | terminals whose windings | are | ||||||
| to | terminals that extend through the | connected in series. |
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| compressor case. | B. The lowest resistance value is the measurement | of | ||||||||
| The terminals are clustered in al trangle ( pyramid ) | ||||||||||
| pattern and, reading from left to right, are identified: | the "run" and "common" terminals. |
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| Start, Common and Run. | C. The |
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| value is the measururement |
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| of the "start" and "common" |
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| terminals. |
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| B + C = A |
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| 2) Measure each terminal and |
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| ground with the ohmmetor |
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| set to the highest range. |
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| If a winding is found to be |
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| either open or shorted to |
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| ground, the compressor |
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| has failed. |
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| Compressor Windings |
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| Operating principle |
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| Inspection method |
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| The overload protects the compressor motor by | 1) Check for continuity with ohmmetor. |
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| responding to both the temperature and current. | - If the overlosd is tripped, | cheak continuity after | ||||||||
| The overload protector is basically made up of | waiting until it has | cooled, | in the room ambient | |||||||
| a set of the contacts normally closed and the | before checking. |
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| bimetal element. | - Even though the continuity of the overload is | |||||||||
| The overload, mounted externally and in direct | observed it is difficult to confirm that the overload | |||||||||
| is operating within the specification limits. |
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| contact with the compressor case, is connected |
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| If there | is any doubt, replace it with a part with | |||||||||
| in series with both windings of the motor. | ||||||||||
| If the motor fails to start for any reason, the heavy | identical specifications. |
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| locked rotor current will cause the bimetal element |
| : An | overload should | NEVER be | ||||||
| to heat which then quickly flex, snapping the |
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| contacts open and interruption current flow through |
| in | the circuit , | not | even | as a temporary | ||||
| the motor. |
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| measure | until | the proper | replacement can | ||||
| Likewise, if the motor overheate to an unsefe leval, |
| be installed. |
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| the comination of current and temperature will cause |
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| the bimetal to snap the contacts open, On cooling, |
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| the bimetal flex back and snaps the contacts closed. |
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| The motor will continue to cycle on the overload so |
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| long as the oriqinal reason for tripping persists |
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8