Engineering manual - SAB 193-233-283 S A-frame (including ATEX)
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008831 en 2020.10
Technical data
6.6 Selecting electric motor
The IEC electric motor types IP23 or IP54 (55) are the motors normally used to drive the
compressors.
Fig. 67: IP23 Drip-proof motor
When selecting an electric motor, the aspects discussed below should be taken into consideration.
6.7 Motor dimension
The motor size is determined on the basis of power demands of the compressor during the current
operating conditions calculated by the Sabroe COMP1 program. Always choose a motor a little
bigger, however:
a. To ensure that the motor has sufficient driving power both during start-up, at minor devia-
tions from the calculated operating conditions and with regard to mechanical transmission
loss, the calculated power demand should be increased by one of the following factors:
1) Air conditioning plant: factor 1.10
2) Other refrigeration plants: factor 1.15
b. Consider which type of plant the compressor is going to work on. The motor must be di-
mensioned in accordance with the following rules:
• For plants where a high ET may be expected, consequently also a higher CT in the
start-up phase, the motor must be dimensioned to meet the high operating tem-
peratures. Usually, there is no need to incorporate factors 1 and 2.
For booster compressors, special consideration should also be given to the choice
of motors.
• Alternatively, the motor can be connected to a system for ampere limitation, which
reduces the compressor capacity until the planned operating temperatures have
been reached. This element is found in UniSAB III, which must be linked to the
Amp. signal. Also in this case, disregard factors 1 and 2.
Note: Please note that for class F insulation motors (105K) for operating conditions like for class
B (90K), approximately 10% continual overloading of the motor is acceptable in relation to the
marking effect.
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