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malec
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Join Date: Sep 2012
Posts: 11

Shorting Resistor

09/17/2012 2:42 AM

What is the method or formula for finding the right capacity of shorting resistor for a wound rotor motor having a frame voltage of 1,073Volts, Short circuit current of 307Amperes and Steps required is 5 steps.

thanks, malec
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PWSlack
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#1

Re: Shorting Resistor

09/17/2012 3:22 AM

Ohm's Law.

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Joshi
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#2

Re: Shorting Resistor

09/17/2012 4:15 AM

Provide some clarity to your post. Where do you use a shorting resistor on a motor? Any sketch you can post?
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TonyS
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#5
In reply to #2

Re: Shorting Resistor

09/17/2012 12:46 PM

"What is the method or formula for finding the right capacity of shorting resistor for a wound rotor motor having a frame voltage of 1,073Volts, Short circuit current of 307Amperes and Steps required is 5 steps.

thanks, malec"

One of these

Connected to one of these

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lyn
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#3

Re: Shorting Resistor

09/17/2012 9:06 AM

1. Find text book.

2. Open text book.

3. Read chapter on shorting resistors

4. Read it again.

5. Look for new job.
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Ried
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#9
In reply to #3

Re: Shorting Resistor

09/17/2012 11:30 PM

Pbbbbth!

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Yahlasit
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#4

Re: Shorting Resistor

09/17/2012 9:59 AM

Yeah, use Ohm's law. Is it a permanent magnet DC motor? Somehow I suspect it is a generator... or are you working on a braking application?

Exactly where do you want your five steps? On a tight rope, being thrown overboard, on the development of the formula, or an accel/decel ramp for you motor?

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Ried
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#10
In reply to #4

Re: Shorting Resistor

09/17/2012 11:32 PM

Double Pbbbth!

At least TonyS had some intelligence for a reasonable answer to a legit question.

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Joshi
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#11
In reply to #10

Re: Shorting Resistor

09/18/2012 12:36 AM

Not reasonable answer but very good answer. I missed wood for the jungle! Wondered where does one use a shorting resistor in a motor. I did not look at the motor starter. My vision got fixed on the motor.
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malec
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#13
In reply to #4

Re: Shorting Resistor

09/21/2012 2:26 AM

Hi! Mr. Layahsit, thanks for your answer for my question but I wanted to know the proper computation on how to find out the exact resistance value of a shorting resistor to be use for a specific wound rotor motor were its application are to regulate speed of a motor due its heavy load.
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Wal
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#14
In reply to #13

Re: Shorting Resistor

09/21/2012 3:28 AM

Have you checked out the link in #6 yet?

It explains very well the mode of operation using shunt resistors on the rotor via sliprings for speed control. It also offers software at a cost that can calculate the resistor values for different operating conditions.

Although it does not detail the computational method, the description it offers may be enough for you to craft your own tool, or at the very least, provide you with further avenues for research in order to find such on the internet.

I'm not sure why you call it a shorting resistor. A shorting resistor by definition is zero ohms which is the value required once the motor has spun up to maximum speed at "zero" slip(I think).

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malec
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#15
In reply to #14

Re: Shorting Resistor

09/24/2012 11:10 PM

your correct, that's why we have steps on resistor resistance apply to a wound rotor motor to regulate its speed not to force all over protective device to trip because of high starting current during starting. gradual rotation will obviously noticed until they reach their full speed at zero % slip.

thanks, malec
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TonyS
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#6

Re: Shorting Resistor

09/17/2012 12:56 PM

Look here http://www.lmphotonics.com/slipring.htm

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Joshi
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#7
In reply to #6

Re: Shorting Resistor

09/17/2012 1:27 PM

Thank you, so very much. Glad to have met you.
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Ried
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#8
In reply to #6

Re: Shorting Resistor

09/17/2012 11:29 PM

Great answer! Not many people know about wound rotor motors (I know I don't!). Your weblink gives some decent information.

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Wal
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#12
In reply to #6

Re: Shorting Resistor

09/18/2012 6:35 AM

Thanks Tony, easy reading. Learned a lot from that.

So, its done with Electrical Calculations software. and will cost $22.

There has to be a place where the method is shown......

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Users who posted comments:

Joshi (3); lyn (1); malec (2); PWSlack (1); Ried (3); TonyS (2); Wal (2); Yahlasit (1)

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