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Selection of Electric Motor
The following are the main guidelines for selection of an electric motor :
1.
The HP of the pump should also be the power output of the electric
motor which is called HP of the motor. However, on practical
considerations, the HP of the motor is always kept slightly more than
what is theoretically required for the pump. Increase in motor HP over
that of the pump should be provided at 20% extra over its HP.
2.
The efficiency of the motor, as declared by the manufacturer, should not
be less than the values given below :
Table 6.10 :Minimum Efficiency of electric Motor (NABARD, 1989)
HP of Motor
Minimum Efficiency(%)
2
3
2
74
3
77
5 and above
80
The motor should have ISI Certification Mark.
3.
Motors conforming to IS : 7538 are to be preferred over other types of ISI
certified motors. Such motors can withstand voltage variation of + 6% to
-15% of the rated voltage. This fairly covers the range of voltage
fluctuation in rural power supply systems.
4.
The motor which has a maximum efficiency for a given HP should be
selected from a group of ISI marked motors. This criteria should
override cost considerations.
5.
Motors for which spare parts are easily available should be preferred.
6.
Motors for which after sales service is easily available should be
preferred.
