5. Selection of Motor and
Coupling
5.1 Electrical motor selection
Select an electrical motor with sufficient power margin
regarding the motor rating. The table below will guide you in
this selection
Example:
• Duty point: 100 m3/h
–
30 m
–
pu
mp
eff
i
c
i
ency
78
%
• Pump
shaft
power: 10.5 kW
• Electrical
motor rating (including margin):
10.5 * 1.25 = 13 kW
• IEC
motor power rating available: 15 kW
5.2 Coupling selection
Standard Pin-bush type flexible coupling is used to connect
top / head shaft to motor shaft.
Couplings can be selected with Cast Iron or Forged steel as
standard material. Select the size of the coupling in accordance
with the recommendation of the coupling manufacturer.
Strictly follow the coupling manufacturer’s instructions for
fitting the coupling between pump and motor. Use torque or
power/100 rpm rating to select suitable coupling in suitable
MOC.
Then check if the rated coupling speed is more than pump
speed.
Also check the motor shaft dia. for selected motor is less than
or equal to the max. Shaft dia. mentioned in the coupling
catalogue.
Additional service factor must be considered in coupling
selection for special applications.
(Refer table on coupling details in CI MOC)
Example:
•
Power: 100 hp, Pump speed: 1480 rpm,
Service Factor: 1
(Power/100 rpm) Rating: hp * 100 * SF / rpm
: 100*100*1/1480
: 7
Select coupling with hp /100 rpm rating more than 7.
• For other types of couplings such Metaflex / Spacer-
Membrane type / Rigid threaded type kindly consult WILO
Mather and Platt.
• Care should be taken to consider and maintain gap between
motor and pump half side of the coupling.
Notes:
• For Forged Steel / Cast Steel MOC kindly contact WILO Mather
and Platt.
• Specified gap to be maintained between pump and motor half
coupling.
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