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Anonymous Poster

How many units are consumed in KW/h ?

01/09/2010 1:47 AM

Hello Proffesionals,

How many units are consumed by 60 HP, three phase 460 volt motor at full load per hour?

your answer are very precious for me .. :)

Thank in advance..for your valuable time.

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Anonymous Poster
#1

Re: How many units are consumed in KW/h ?

01/09/2010 1:59 AM

45 KWH

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Anonymous Poster
#2

Re: How many units are consumed in KW/h ?

01/09/2010 6:24 AM

mechanical:

1 HP = 0.746 KW

60 HP = 60*0.746 KW

Electrical Power

= mech power/ motor η

But that depends on the motor loading. It is highly unlikely (unless it is homework) that 60HP motor is loaded at 60HP

Units consumed in KWH (not KW/H) = KW * no of hours (1 for you)

= KW calculated as above.

- You must know motor loading,

- Efficiency at that load.

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Anonymous Poster
#3

Re: How many units are consumed in KW/h ?

01/10/2010 2:07 AM

Don't forget the utility's premium for starting and running it!

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Guru
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#4

Re: How many units are consumed in KW/h ?

01/10/2010 4:45 AM

It depends upon how much of the motor's 60hp capacity is utilised.

Say it is fully loaded. 1hp ≈ 746W, which comes out at ~45kW, and there will be a bit more to account for motor losses, say 10%, which comes out at approaching 50kW. So the maximum it could be is around 50kW = 50kWh per hour = 50 "units" per hour, though it does rather depend upon how well loaded it is: if it is spinning freely and not doing much work then it will be far less than this though one might want to switch it off to save a bit on the tariff, particularly if there is a low power factor penalty on it.

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Anonymous Poster
#5

Re: How many units are consumed in KW/h ?

01/10/2010 6:03 PM

At 60 HP, (60 x 0.75) / Power Factor would be the no of units consumed per hour at full load.

I.e., if the power factor you can maintain at abot 0.9,

60 x 0.75

--------

0.9

= 50 KWH power consumption,

i.e. 50 units per hour would be consumed.

Regards,

Ashok Shukla

Delhi

9810145598

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#6
In reply to #5

Re: How many units are consumed in KW/h ?

01/11/2010 7:26 AM

Hello Ashok - what you wrote would be correct if you substitute efficiency for power factor.

Changing power factor does not change the no of units (kWh) consumed. Depending on the tariff, it might change the amount you pay the electric supplier, but that's another story.

On the other hand, efficiency does affect it. I don't think any other poster has mentioned it, but a 60 HP motor produces 60 HP shaft power (at rated load). The input electrical power is greater. Of course, as others have said, it may not be operating at rated load.

Cheers.........Codey

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Anonymous Poster
#7
In reply to #6

Re: How many units are consumed in KW/h ?

01/11/2010 8:02 AM

Missed me at #2

Electrical Power

= mech power/ motor η

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#8
In reply to #7

Re: How many units are consumed in KW/h ?

01/11/2010 10:15 AM

Yes, you're right, I did. Sorry!

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Anonymous Poster
#9
In reply to #8

Re: How many units are consumed in KW/h ?

01/11/2010 1:00 PM

Never mind This is the reason the the GAs are important in a post as I have stressed many times. It keeps away the redundant (not the OTs of course) from the ones that one should read before adding a new aspect.

But unfortunately still GAs are given on names and not posts.

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