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ZAFRUL
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Join Date: Mar 2014
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Chang In Shaft Power When Speed Is Reduced

03/05/2014 7:27 AM

Consider a 50 kW motor operating a variable torque load. What would be the change in shaft power when the speed is reduced by 180 rpm?

a. 10.0 kW

b. 13.5 kW

c. 20.0 kW

d. 36.5 kW

e. None of these answers
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PWSlack
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#1

Re: Chang In Shaft Power When Speed Is Reduced

03/05/2014 8:13 AM

Arrrrrrrrrrrrrroooooooooooooooooooogah! Homework alert!

One wonders what the change would be if the shaft was only doing 180rpm in the first place...

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#3
In reply to #1

Re: Chang In Shaft Power When Speed Is Reduced

03/05/2014 9:05 AM

No hints. That wouldn't be fair to the other cheaters students.

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Mike W
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#5
In reply to #1

Re: Chang In Shaft Power When Speed Is Reduced

03/05/2014 1:40 PM

or 90rpm . . .

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#6
In reply to #5

Re: Chang In Shaft Power When Speed Is Reduced

03/05/2014 2:13 PM

Ohh! That one has to be 'e'!

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Fredski
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#2

Re: Chang In Shaft Power When Speed Is Reduced

03/05/2014 8:22 AM

we dont do your homework here
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Tornado
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#7
In reply to #2

Re: Chang In Shaft Power When Speed Is Reduced

03/05/2014 11:54 PM

We also don't tell your instructor how to form proper questions.

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Tornado
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#4

Re: Chang In Shaft Power When Speed Is Reduced

03/05/2014 11:03 AM

Insufficient information; it depends on what the original rpm was.

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WolfDrago
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#8

Re: Chang In Shaft Power When Speed Is Reduced

08/28/2015 1:39 PM

This question is from the pdf version of the PEM (Professional Energy Manager) exam available through Schneider Electric's Energy University.

The pdf version is missing a key piece of information that the motor was originally running @ 1800 RPM. This number will show up when you take the actual exam online.

Anyway, the right answer is b. 13.5 kW.

(@1620 RPM, the demand will be 36.5 kW, so the change is 50 - 36.5 = 13.5 kW)

Good luck if you're taking the exam!

-WolfDrago-
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Fredski (1); Mike W (1); PWSlack (1); Tornado (2); truth is not a compromise (1); Usbport (1); WolfDrago (1)

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