7.OPERATING PRINCIPLE OF MAJOR COMPONENTS, AND INSPECTION METHOD

7-1.Compressor Motor

 

Operating principle

 

 

Inspection method

 

 

The compressor motor, mounted directly to the

1) Measure

the

resistance

of each winding of

the

 

compressor and located inside a sealed steel

compressor.

 

 

 

 

 

 

 

case, has two windings.

a. Disconnect the power cord.

 

 

 

One is a start winding and the other a run winding.

b. Remove the relay from the compressor.

 

 

The windings are connected together internally,

C. Measure the resistance of each winding.

 

 

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 glass-sealed

terminals that extend through the

connected in series.

 

 

 

 

 

 

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.

 

 

Start, Common and Run.

C. The mid-level resistance

 

 

 

 

 

 

 

 

 

 

 

 

 

 

value is the measururement

 

 

 

 

 

of the "start" and "common"

 

 

 

 

 

 

terminals.

 

 

 

 

 

 

 

 

 

B + C = A

 

 

 

 

 

 

 

 

 

2) Measure each terminal and

 

 

 

 

 

 

ground with the ohmmetor

 

 

 

 

 

 

 

set to the highest range.

 

 

 

 

 

 

 

If a winding is found to be

 

 

 

 

 

 

 

either open or shorted to

 

 

 

 

 

 

 

ground, the compressor

 

 

 

 

 

 

 

has failed.

 

 

 

 

 

 

 

 

Compressor Windings

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

7-2 Overload Protector

 

 

 

 

 

 

 

 

 

 

Operating principle

 

 

Inspection method

 

 

The overload protects the compressor motor by

1) Check for continuity with ohmmetor.

 

 

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.

 

 

 

 

 

 

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.

 

 

contact with the compressor case, is connected

 

 

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.

 

 

 

 

 

locked rotor current will cause the bimetal element

 

: An

overload should

NEVER be by-passed

 

to heat which then quickly flex, snapping the

 

 

 

 

contacts open and interruption current flow through

 

in

the circuit ,

not

even

as a temporary

 

the motor.

 

 

measure

until

the proper

replacement can

 

Likewise, if the motor overheate to an unsefe leval,

 

be installed.

 

 

 

 

 

 

the comination of current and temperature will cause

 

 

 

 

 

 

 

 

 

 

the bimetal to snap the contacts open, On cooling,

 

 

 

 

 

 

 

 

 

 

the bimetal flex back and snaps the contacts closed.

 

 

 

 

 

 

 

 

 

 

The motor will continue to cycle on the overload so

 

 

 

 

 

 

 

 

 

 

long as the oriqinal reason for tripping persists

 

 

 

 

 

 

 

 

 

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