Motor burn outs

[bernard]

Hi

Spoke to someone who was having trouble with2 3-phase motors runing 2 sabroe compressors.Info is limited at this stage but will try and get more during the week.One motor kept tripping breaker so it was rewound but still trips breaker.Now the other motor has gone down to earth.I would think it is caused by voltage surges or phase imbalance,is there an insturment to moinitor the voltage over a period.Or can someone give me a few pointers

Regards Bernard

[bernard]

P.S Star delta contactors have been changed also plus breakers



Regards Bernard

[Andy W]

Where do you start, check the obvious first, voltage on to the motor, then voltage back at the fuse board, is there much of a voltage drop, is the power supply on the factory adequate or do the lights dip when something starts up, are the phases balanced out on the fuse board, have you thought about fitting more sensative thermal overloads on the contactors, do the motors have thermistors, are they connected. Regarding your original question, yes you can hire all kinds of instruments for the monitoring of voltages etc Abacus Instruments I think, but dont ask where as it is going back a few years, but I would check out the above first. I once had a problem where the wrong motors were selected and they would struggle to start a fully loaded compressor, I dont suppose the compressor is "tight" is it and if it is SD do the unloaders work on start up....have had that before!

[benijoseph]

Hi

Spoke to someone who was having trouble with2 3-phase motors runing 2 sabroe compressors.Info is limited at this stage but will try and get more during the week.One motor kept tripping breaker so it was rewound but still trips breaker.Now the other motor has gone down to earth.I would think it is caused by voltage surges or phase imbalance,is there an insturment to moinitor the voltage over a period.Or can someone give me a few pointers

Regards Bernard

MR, Ber.

check for the max amps of the motor and connect SINGLE PHASE preventer . make sure that compressor is not over loading the motor? less chance of surges!
beni joseph.

[Carlo Hansen]

Hi bernard.

If you are looking for a good instrument to measure power
and power failure, take a look at this link.
I use a UMG507 for testing.

http://www.janitza.de/

Best regards
Carlo Hansen

[botrous]

If you are interrested in building your own AC 3 phase protection board i can send you a schematic that i designed my self , it's a full voltage and phase protector , that disconnects the motor for phase loss , voltage drop or voltage raise in any one of the three phases.
nb : you should have a basic knowldge in electronics and electronic components to assemble it.

[bernard]

Hi botrous

Yes please,I have some qualifications in that area.I willsend you my e-mail address.

Regards Bernard

[chemi-cool]

Hi Bernard.
Rule No.1 - Always, when replacing an electric motor of any kind, over 5 HP. Change also, starting contactor and circuit breaker!
Start fresh.

Rule No. 2 - never restart a motor that tripped before you check and find the reason for the problem.

make a habit' to take apart, contactors and circuit breakers to check the contacts inside. You will be amazed by the information you will get from doing it.

I reckon that 0ver 90% of compressor burnouts are related to bad contacts inside contactors and circuit breakers.

It is important to use a CB big enough so the desired currant draw, will be in the middle third of the scale.

Please, let me know the situation of these contacts.

The instrument used by Carlo Hansen is a fine one but it is more of lab instrument then one you throw into the back of the van.

Chemi

[botrous]

ok bernard , I'm waiting for your email adress to send you the diagram.