# Motor Power

2 replies to this topic

### #1 Rzn

Rzn

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Posted 13 October 2006 - 02:52 AM

Dear All,

We have a vacuum blower working at a corrugated machine. It has an eddy current motor 400vac, 50HZ, 15KW and 1390RPM. Vcc blower is driven through V belts. The size of both pulleys is same. Now the life of vcc blower is over and we want to replace it. I want to increase the rpm of blower up to 20% by decreasing the size of its pulley. What is the formula for calculating the desired KW of motor? Someone told to me that this new application requires more than 50% more power of motor (22.5KW). Is it true? I want to know the proper formulas.
Any help will be highly appreciated.

### #2 jOmega

jOmega

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Posted 13 October 2006 - 02:34 PM

The vacuumn blower is undoubtedly a centrifugal load type device.

As such, POWER is proportional to the cube of the speed.

In your case, you want to increase the speed by 20% : from 1390 rpm to 1688 rpm.

Here's the math:

1688 ÷ 1390 = 1.2

1.2 ^3 = 1.728

15 kW x 1.728 = 26 kW

A 30 kW motor should handle the additional power requirements without any concern.

NB!
Verify that the Eddy Current Coupling is rated for the additional speed and power transmission.

### #3 Rzn

Rzn

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Posted 14 October 2006 - 02:20 AM

Dear jOmega,

Thanks for your useful information. I would apply and inform members in this forum for this kind of experience.
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