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Motor calculation for various applications.

1. Pump motor.

Pump motors are calculated using the following equation.

 / 3600 P = W ã = N/m3 Q = m3/h h = m n =

where :

ã stands for the fluid specific weight in  Í/m3 (9810N/m3 for water and  8000 for petroleum).
Q stands for pump flow capacity in  m3/h.
h is the discharge height in m
ç is the motor - pump system total efficiency factor  (0.50 ~ 0.70).

2. Lifts , elevators and cranes.

Motors for these applications are calculated using the following equation

 x 9.81 P = W G = kp v = m/s n =

where :

G is the maximum load to be lifted in  kp (1kp = 9.81N).
v is  the elevation velocity in  m/s.
ç is the motor - pulley system total efficiency factor  (0.50 ~ 0.70).

When calculating  person lifts G we must add  75kg (=kp)  for each person.
If there is a contraweight we must divide the work load by 2.

For a  10 person lift with a contraweight , the load for the equation is
10 x 75kp = 750kp / 2 = 375kp

3. Fan - compressor motors.

Motors for these applications are calculated using the following equation

 x 27.7777 P = W Q = m3/h Dp = bar n =

where :

Q is the air flow in  m3/h.
Dp is pressure raise in  bar =105  Pa (N/m2).
ç is the motor - fan (or compressor)  system total efficiency factor  (0.50 ~ 0.70).

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