Old WRIM Motor 2

[petronila]

Dear All,
The question is : One Old WRIM,Westinghouse-100 HP-1165 RPM-230/460 Volts. 242/121 Amps. Rotor: 360 Volts-130 Amps was working in a Hoist Crane, the rotor fails due to slip rings shorted.
The WRIM was sended to one shop and they change the slip rings.But the motor don´t work proper.
Before the slip ring failure, the craine was lifting the
weights drawing by the rotor 130 Amps Max and 70 Amps Min.and 121 Amps by the stator.

Now with the New slip rings and the same rotor´s winding and same above loadding conditions the WRIM drawns in the rotor 230 Amps and works slowly, the rotor current stays stable in this value.
We was tested the rotor windings with megger and Surge tester with 2000 Volts with good results.We was warmed the rotor winding at 100 C and it was tested again with good results too.
We was tested also the Rotor Core inyecting 10 Volts to the shaft 570 Amps circulating. In three minutes the current rise to 627 Amps and the core temperature was : 44-39 y 38 C in differents sectors.

We know the problem is not the control or the resistance starter due to in this moments the crane is working with a other spare WRIM with same name plate.

What think about this problem??

 

[waross]

Are there any other rewind shops in the area?
respectfully

 

[edison123]

Did you do a open circuit test and check the rotor induced voltage ?

 

[taxidi]

Hi,

You say the rotor fail, was the rotor rewound???

If it was, they must have internally connected for Star instead of delta; it would explain the lack of torque and the increase of currant under load.

What kinds of rotor control system do you have, resistor/relay or liquid????

Did you check if the ring short did not damage this control?

Hope this help you, please give me more info, I will found your problem.

Regards

 

[edison123]

How did you measure the rotor current, which is at low frequency ?

 

[Marke]

Hello petronila

I wold certainly recommend measuring the open circuit voltage. If the opencircuit rotor voltage does not equal the rated secondary voltage, then there is a possible problem with the rotor connection. NB the rotor should not develop torque with the rotor open circuit, if it does, then there is a rotor problem which may be in the windings, or the terminations.

Best regards,

Mark Empson

http://www.lmphotonics.com

 

[petronila]

Thanks for the answer,

Answers: 1.The rotor´s current was read with a digital AC clamp at 60 hz 2. The rotor was not rewound due to pass all test. 3. The WRIM was working proper and fails, the shop finds a short circuit in the slip rings, they only disconnect the old slip rings and replaced by a new ones, the rotor is only three leads no chance to mistake in external connections.4. The current data was taken in operation Before the failure, the craine was lifting the weights drawing by the rotor 130 Amps Max and 70 Amps Min.and 121 Amps by the stator.5.The control system is by Resistors and once the WRIM fails we mounted an spare WRIM an it is working proper to weaks ago.

Thanks for the INPUTS.

Petronila

 

[petronila]

Dear All,

The open circuit test don´t indicate any problem.

Thanks Marke and Edison.

We was wondering about the fail and taking acount the only work done was the sliprings replacement so the problem could be centrifugal. We try this test:

The rotor was placed in the lathe and some brushes was riged to slide on the slip rings. We surge test the rotor, unil the rotor was rotate.The rotor was speeded close to high lathe rpm and the test was continue,we find the surge pattern becomes bad at high speed. It indicates that some lead or leads are probably lifting and shorting against the ring .Now the shop is rewinding the rotor and replacing the sliprings.

Thanks again for your help.

Petronila

 

[stardelta]

Thats the type of info that makes things easy for us repair guys and gives you Kudos with the customer. Nice one Petronila...have a star.

 

[edison123]

Petronila

That was a great detective work deserving a star.