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VST
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Joined: 9-May 08
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Last Seen: 18th February 2010 - 10:54 AM
Local Time: Mar 16 2010, 02:42 PM
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8 Aug 2009
Recently we have faced some problem in AC drive . Whenever we switched off ac power of the drive, there was a ac voltage generated at input terminals. This voltage was present as long as the DC link was present.and reduced proportinally.All the lamps and other logic contactors were chattering. This drive is having thyristorised rectifier stage.
I am unable to find the exact cause of happening . There is absoultly no other problem with drive. I have not obsrved such things in any other drive. What may be the reasons.?
12 Jun 2009
Dear Experts,
I need your help. We are in process of upgrade of our Motor test set up facility. Our Engineer had given a scheme in wich the Motor will be having Regenrative units connected to it. this will fed energy back to supply grid.But many times we used our Internal D.G set to fed the supply for factory. Unfortunately he has not considered this situation. Can any body put light on this .What will be the generators reaction.What precautions to be taken?
8 Jul 2008
Few months ago while testing a Micro master series AC drive (Siemens Make) I faced following problems.
Unit was powered up successfully. There was no motor connected at Output. As soon as the ON command (Drive Run) was given, Drive tripped with DC Link over voltage fault. The display value of the dc link as well as the Measured Value with Meter both was rising rapidly with On command and causing trip. There was no external reasons like Fast Decelerating, Breaking or an over voltage condition at Input. Subsequently the repair Engineer open the drive and found one support Rod from the Body of drive was touching to the output phase .( Causing Direct short circuit of phase to Earth terminal.) After removal of this short drive worked very well. But the questions remain unanswered
2 Jul 2008
One of the morriss Crane in a factory was retrofitted last year by a contractor. But since then it is been used very rarely. Last month this crane failed four times in the span of 15 Days. All the four times problem was in its Incoming section of rectifier and precharge circuit. Inverter section never went faulty. All the failures were only in Long Travel drive. L.T drive is used to drive four motors parallel. Replacing the defective cards Drive was repaired every time. But reason for the failure was untraceable. The input contactor found short few times. And was replaced. The fourth failure was with Damaged Precharge resistor as well as the welded input Contactor. Interaction with customer has enabled us to think more, following points were enlightened.
We strongly suspect on the operation and installation of this radio receiver. This is mounted just near to L.T panel. And have used many interlock for operation. Mains contactor was also enabled through Radio remote. Hence we suggest to by pass this radio remote temporarily. And simultaneously replaced the Breaking Module. Since then the drive is working very fine. Trials were taken continuously for 1 week And drive never tripped with Under voltage fault. As it was hard to believe for people that radio remote can produce this type of damage to drive, as they had multiple reasons in favor of it. Everyone was suspecting the replaced Breaking Module. The breaking Module (50Kw and 40Amp max) is tested separately and found perfectly ok. I have read somewhere that range of RFI generated by drive is around 7 MHz. And Radio remote is working on 443Mhz.Again it is difficult for me to explain how can these create damage to inverter. Do any one have some inputs for me.
9 May 2008
Dear Sir,
All inverters are specified that Output voltage can be max equal to input voltage(Ac to AC converter). Is their any inverter available, which can provide more output voltage than the supply voltage. Regards, |
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Lo-Fi Version | Time is now: 16th March 2010 - 09:12 AM |
23 Sep 2008 - 12:21