brake horse power

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Jay Pai

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I have an application (duplex lift station) where there are 2 motors...mechanical specs call for 7.5BHP for each motor. What is the difference between "braking horse power" and "horse power" in terms of full load amps?

Theoritically both pumps can be running at the same time...do I figure 11FLA for each motor...and size the breaker for 30A?

Currently I have specified a 40A breaker to feed the lift station to be on the safe side.
 
Re: brake horse power

In this application you need to take the largest motor at 125% plus the sum of the other motor(s). Since they are the same size, I get 25 amps. If you are using a breaker as the short circuit / GF OCPD, you can size it at 250%.

Most of the lift stations I have put in come with schematics which usually give the MCA or MCOP. If you have those, you need to follow that.
 
Re: brake horse power

Sorry, I didn't answer your question on brake horsepower:

Brake or shaft horsepower is more commonly used to indicate the practical ability of the engine, or the maximum performance, which is the indicated horsepower minus the power lost through heat, friction, and compression.

This is as it relates to engine performance.
 
Re: brake horse power

Originally posted by Jay Pai:

What is the difference between "braking horse power" and "horse power"
Click to expand...
True horse power is what is doing the pulling in this photo.

Breaking horse power is what I am doing to the horse.

holdingthehorse.jpg
 
Re: brake horse power

Please, please, do not answer Bob's question. There are some things that us city slickers just don't want to know! :D
 
Re: brake horse power

"Brake horsepower" comes from the use of a rig known as a Prony brake. A brake shoe is wrapped around a flywheel. The shoe is connected to a scale, and the BHP can be figured from the scale reading, the angular velocity, and the radius of the flywheel.
 
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