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Liquid Starter |
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 Aug 19 2008, 06:51 PM
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#1
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 Group: Members Posts: 1 Joined: 19-August 08 Member No.: 4,758  |
Dear All
Hope you are all doing well Appreciated your support in the following in our cement plane, while performing an In Rush test on "Cement Mill Main Drive" while starting the current profile was unexpected the starting current was almost 200% FLA and at the END step of the electrolyte "while the short circuit is on" the current reaches 380% FLA, i have noticed between these two events that the current after starting and before the end that the current is almost constant at 80% FLA. I think that the problem is in the Electrolyte but i need an AC Impedance Tester to measure the Impedance and i can not find it your support is kindly appreciated |
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Aug 19 2008, 07:15 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 ahmed osman
Welcome to the forum. The initial start current at 200% is fine. As I understand your post, the current then drops to 80%, and then steps to 380% when the shorting contactor closes. This is due to the resistance of the electrolyte when the shorting contactor closes. As the resistance is increased, the slip at which maximum torque occurs increases, so for a given load, the maximum speed reduces. If you short the rotor at reduced speed, you will get an increase in rotor current. 380% is not too bad, but if you could reduce the resistance before you short the rotor, the current peak would be less. The resistance can be reduced by more immersion of the electrodes, or by increasing the strength of the electrolyte sloution. If you reduce the resistance at start, the initial start current will increase. This is why mulitple stages of resistance are commonly used, or variable resistance liquid starters are used. Best regards, Mark. -------------------- 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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