Support
EXAMPLE : R = Running winding S = Starting winding C = Common winding E = Earth terminal
R to C = 3.5 ohms S to C = 10.2 ohms R to S = 13.7 ohms
3.5 + 10.2 = 13.7 ohms
With regards to the second part of your question : The function of a multiple-winding motor is to provide a selection of running torques which , when driving a load such as a blower wheel , will result in varying speeds and thus affects air flow volumes .
Supplied
Multi Speed motor windings .
Note : The resistance of some undamaged windings can be as low as 0.5 ohm . Zero resistance indicates a shorted winding and an infinite or very high resistance indicates an open winding .
Use an insulation tester when checking for a grounded winding . Current is passed through the weakness / breakdown in the insulation material to the other winding or to earth . Unless you have specific information indicating otherwise , any hermetic motor of one horsepower or under can be considered suspect if the resistance between the windings and the housing is less than 0.5 meg-ohm .
Test as follows : E to R = less than 0.5 meg ohm ( Earth to Run ) E to S = less than 0.5 meg ohm ( Earth to Start ) E to C = less than 0.5 meg ohm ( Earth to Common )
If all the readings test correct the compressor can be run . Using a tong tester take the ampere reading while it is running . The amp reading should correspond with the ampere rating on the compressor while under operating conditions .
The above is extremely important , so I would recommend that you check all compressors ( even new ) prior to connecting the power supply . If a fault is found prior to installation of the compressor the warranty claim should be simplified . An incorrectly connected motor can burn out within a few seconds , so double check your connections to safeguard against burning out motors .
The connections shown are for low speed . For higher speeds switch the input from A to B , C or D .
The capacitor in series with the motor windings serves a dual function : it improves starting torques and provides better running efficiency . Of late , Variable Speed Drives with associated controls are becoming more and more common place . ( See previous
RACA Journal issue )
The name plate or data contains all the information required for the installer . You may find some variation between manufactures , so always check .
Meaning of information
Ser . No . Vd 5157 / 74 :
Frame T . E . F . C . / D132S TEFC : D132S :
kW : Volts 380 : Amps12,6 :
RPM : Conn :
Brgs 6208 D :
The serial number of the motor
Totally enclosed fan cooled
Indicates the distance between the mounting and the shaft centre
Indicates total motor output at sea level Working volts of motor
When the motor is at full load current draw is 12.6 amps
1 450 = 1 450 revolutions per minute Star connection or Delta connection Bearing drive end = size / type 6208
6206 ND : Bearing non drive end Duty : S1 C . M . R .
S1 or C . M . R .:
S2 :
Motor can run continuously without having to stop to cool down
Motor can run for up to 60 minutes before stopping to cool down
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RACA Journal I April 2023 www . refrigerationandaircon . co . za