This workbook contains three short relationships that will help you find the motor power that is required for your application. I have included the following applications:

- Pump motors
- Lift/elevator/crane motors
- Fan/compressor motors

All the relationships are based on a total efficiency factor, which for most of the cases can be considered something between

**0.5 and 0.7**. Of course these relationships do not substitute an analytical calculation, but, could be useful for a quick reference.**Calculations**

The calculations are based on the following relationships:

**1. Pump motors**

where:

P: Pump motor power

γ: Fluid specific weight

Q: Pump flow capacity

H: Discharge height

η: Motor - pump system total efficiency factor

P: Pump motor power

γ: Fluid specific weight

Q: Pump flow capacity

H: Discharge height

η: Motor - pump system total efficiency factor

**2. Lift/elevator/crane motors**
where:

P: Lift/elevator/crane motor power

G: Maximum load to be lifted

v: Elevation velocity

η: Motor - pulley system total efficiency factor

where:

P: Fan/compressor motor power

Q: Air flow

ΔP: Pressure raise

η: Motor - fan (or compressor) system total efficiency factor

If you have different units than those used in the relationships above you can download the units converter that I developed some months ago.

This file can be opened with

P: Lift/elevator/crane motor power

G: Maximum load to be lifted

v: Elevation velocity

η: Motor - pulley system total efficiency factor

**3. Fan/compressor motors**P: Fan/compressor motor power

Q: Air flow

ΔP: Pressure raise

η: Motor - fan (or compressor) system total efficiency factor

If you have different units than those used in the relationships above you can download the units converter that I developed some months ago.

**Download it from here**

This file can be opened with

**Office 2007**or newer. Please, remember to enable macros before using the workbook.**Did you like this post? If yes, then share it with your friends. Thank you!**