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Nishant
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Why More Current Carrying when Motor On Load

08/17/2007 3:27 PM

Why More Current Carrying when Motor On Load

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#1

Re: Why More Current Carrying when Motor On Load

08/17/2007 3:39 PM

The current is proportional to the load.

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Nishant
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#2
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Re: Why More Current Carrying when Motor On Load

08/17/2007 3:44 PM

Thank You For Replying

But Sir

What happen on flux/Winding/Rotor so Motor Current Increase ?

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GW
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#4
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Re: Why More Current Carrying when Motor On Load

08/18/2007 12:17 AM

An ac motor running no load with constant AC voltage applied has an inductive magnetizing current with a lagging power factor. The no load losses will give it a small real power loss component. As the motor loads up the power (real power this time) increases and since it is real work the power factor is unity for that component. The total current is the vector sum of the (reactive magnetizing current) plus the orthogonal component of (the work done plus heat losses current).

Very simplified of course.
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#9
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Re: Why More Current Carrying when Motor On Load

08/18/2007 1:31 PM

When the motor spins, it acts as a generator and produces back emf opposing the applied voltage. When it is loaded down, it slows down, producing less back emf. The applied voltage minus the back emf is then greater which drives more current through the windings, which produces more torque from the motor.
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GW
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#3
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Re: Why More Current Carrying when Motor On Load

08/18/2007 12:10 AM

Thats two too's!
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Anonymous Poster
#5

Re: Why More Current Carrying when Motor On Load

08/18/2007 1:25 AM

magnetic flux is permitted to enter the moving portion until it moves or saturates. Thus the apparent reactance of the motor changes. The force on the rotating shaft will rapidly increase. sorry i don't know the difference between stator, rotor, armature, etc.
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#6

Re: Why More Current Carrying when Motor On Load

08/18/2007 4:26 AM

Oh! No!
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#7

Re: Why More Current Carrying when Motor On Load

08/18/2007 7:23 AM

There is no free lunch.

The no load current is what is needed to turn the motor alone, the rest is for when the motor is doing some work eg. its loaded up......seems very logical to me!

You need more gas to the engine when driving a car up hill (load) as when on the level or going downhill......

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ag_okara@yahoo.com
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#8
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Re: Why More Current Carrying when Motor On Load

08/18/2007 9:36 AM

when the motor runing on no load the diferrence is very small between stator field flux (speed=120f/p)and rotor speed so slip will be low as(slip=ns-n/ns*100)where ns=stator field rotating speed and n=rotor speed.

when motor on load the speed of rotor decreaes and slip increases also rate of change of fliux increases so with rate of change of flux increases the current also increaes'

abdul ghaffar

mubashar ahmed
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