unstable ampere in motor 3300 V 1250 HP

[martense]

Hi Guys,
i have a trouble with my motor with name plate bellow :
Voltage : 3300 V
RPM : 3000
Ampere : 180 Ampere
HP : 1250 HP

the problem is when i each time i start the motor the ampere is not stabel for about 15 second around 17-24-40 ampere and after that the ampere is stable 25 ampere (No Load). and for the 15 second the motor sound rought.
this motor using metal bearing.
need opinion non this..
thank you

regards,
Marten

 

[jraef]

Bearing issues would not show up as a severe phase current imbalance like that. It sounds more like you have a problem in your motor starter that is causing a partial phase voltage loss: for instance high resistance in one phase because of a bad contact. The current imbalance will create negative sequence currents with a high DC content, essentially making the motor fight itself as it tries to accelerate.

Check your starter very thoroughly before you do some serious damage to that motor.


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[electricpete]

What is the motor driving?
How long does it take to get up to speed?


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[electricpete]

By the way - does 17-24-40 represent a reading of each of three phases, or three sequential readings of a single phase?

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[martense]

the three phases ampere is balance but the ampere is up and down for 10second for first start...17 24 40 24 40 17 sequential

 

[waross]

Please describe the bearings in more detail. Is the motor on turning gear before being started?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[edison123]

25 amps no-load on a 180 amps machine ? That's too low. Was the motor rewound ?

 

[martense]

the motor not rewound but just being overhaull... do you know the no load standart for 180 amp machine 3,3 kv?
the bearing is metal bearing not ball bearing...
what could be the possible the cause of the first start up and down ampere for first 10 second and the rought sound?

 

[Skogsgurra]

You say 3000 RPM sharp. Is this a synchronous machine?

If so, the excitation is usually high at start and does sometimes make the pole angle oscillate.

First question: Is it synchronous?

Second question: Has anything been done to the excitation system?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

Is there a pressure lubricating system or do the bearings use oil rings or oiling chains to carry lube oil up to the bearings? A large motor with oil rings or chains should be rotated slowly either on turning gear or manually until the bearings are well lubricated before being started. The friction is very high and the bearings may be damaged if such a motor is started without being "Rolled over" first.
I remember a startup that involved manually rolling four, 3000 HP motor generator sets each night before starting them. They took a crew of from four to six men to roll them over until the oil worked into the bearings.

Bill
--------------------
"Why not the best?"
Jimmy Carter