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Rotor Failure And Earth Fault |
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 Feb 17 2008, 07:08 AM
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#1
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 Group: Members Posts: 1 Joined: 17-February 08 Member No.: 4,295  |
I amusing a 112kw slip ring induction motot on a crane hoist. The motor failed and upon investigation, we found a damaged cable and the rotor had developed a short circuit between phases.
The dilemma is, we have a short circuit on the rotor, and the supply is tripping on earth fault, instead of overload as I have expected. I cant explain that! |
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Feb 18 2008, 05:54 PM
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#2
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Posting Freak Group: Moderator Posts: 2,336 Joined: 24-April 02 From: Christchurch, New Zealand Member No.: 1 |
Hello emms
Welcome to the forum. It sounds to me as though you have tow faults, one on the stator and one on the rotor. I would not expect a rotor problem to bring up an earth fault unless there is an earth connection in the starter also and the earth fault is derived by monitoring the current flowing in the earth conductor. Best regards, -------------------- Mark Empson administrator
Skype Contact = markempson | phone +64 274 363 067 LMPForum | LMP Tech Warehouse | L M Photonics Ltd | Empson family | Advanced Motor Control Ltd | LMP Software | Mark Empson Website |
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Mar 21 2008, 04:16 AM
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#3
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Junior Member Group: Full Member Posts: 7 Joined: 19-March 08 Member No.: 4,399 |
Dear all
We may consider motor as a rotating transformer , with air gap as the flux tranfer medium Now if a secondary earthfault in a transformer can reflect in the primary , why not in a motor+++ provided the stator winding is star connected ????? Kamath |
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