Motor Starters Fail

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CCCI

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Orlando, Florida
I replaced a motor starter that has been working for about six years. The new one lasted about 1 week. I replaced it again and it lasted about 4 weeks. This is a 9.2 amp 480v motor going to a pump. It is not on a VFD and every time that I test the power it checks out fine. The amperage loads and tempature are also fine.

This is a Size 1 motor starter with a 120 volt coil.

I am with maintenance and I had a electrical contractor check it out this last time and they could not fine the reason that we are frying motor starters.

The power going to the coil reads 125 to 130 volts. Can the power supply to the coil go out and still read 125-130 volts later?

I read 80 to 100 HZ with a Fluke 189, but an enginneer that works here says that I could be getting wrong readings because we have VFD on other motors in the same MCC.

I believe that it is the motor but another person says that they have checked the motor and it is fine. How can I find out if it is the motor?
Do motors cause problems like this?

Could a bad VFD cause problems with a none VFD in the same MCC?

The 20 Amp breaker has not tripped and the heaters have not blown.

Thank You to anyone that can help. This has cost $600.00 in motor starters and $500.00 for the electrical contractor to do what I have already done.

Michael Hester
Electrician
Campus Crusade for Christ
 
You say that you are "frying" the starters.....

Is it the coil that's getting fried?

Have you checked the amperage draw on the coil itself?

The coil (I believe) should be rated in watts.....what is this number?

You may need to put a correctly sized fuse in the circuit feeding the starter coil.
It won't fix the problem, but it will keep you from frying the coil.

I can visualize how having the starter in the same circuit as a VFD can cause a increase in hz on the starter coil.

I'm not sure exactly what having 80-100hz on the coil will do, but I suspect that it will cause the coil current to increase.

How is the starter controlled....pushbutton?...selector switch?...auxiliary contact?...etc?...

Was the original starter operating in the same scenario?

What brand is the starter?

steve
 
Coil Is Good

Coil Is Good

The coil is good. It is the contactor points that are frying.

The original starter was operating in the same scenario for years.

The coil is 59.9HZ

The 80-100HZ is on the contractor It is the power on the contactor and that may not be a true HZ reading. That is what I am reading with a Fluke 189, but is that a wrong reading or not?

It is a GE CR306C002 NEMA Size 1

It is controlled by auxiliary contacts.
 
It is controlled by auxiliary contacts.

Just something to look for I have had auxiliary contacts that chattered, causing the coil to pull in and out and overheat. May have been what got the first one.
 
hockeyoligist2 said:
It is controlled by auxiliary contacts.

Just something to look for I have had auxiliary contacts that chattered, causing the coil to pull in and out and overheat. May have been what got the first one.
Click to expand...


Good call.
If the power contacts are chattering, it will definitely cause them to burn.
Since it's a new starter that's failing early, I'd look at the control circuit.
Does the starter "buzz" loudly when the motor is running?

steve
 
As this is a pump motor, what is turning it on/off ? A float switch ? How many times an hour is the motor starting/stopping ?

What are the actual amp draws on all phases ? What is the actual running voltages between all phases ?

A size 1 starter can do 27 amps / 10 HP. What is the name plate HP & FLA of the motor ?

We're presumming it's a 460vac motor with a 480vac source.

Is it the same phase contact that is burning up ?

As far as the aux contact, where/how is that wired ?

Has anyone actually looked at the heaters part number and checked the size ?

I thought that this starter has replaceable contacts.
 
motor starter fail

motor starter fail

sometimes pumps will stop or slow down due to bearing ,something in the pump I don"t think your problem is motor more the pump.Just might have to baby sit this pump with a amp.meter,after it warms up or runs for a while amperage will increase ,maybe pump bearing will get hot touch it and check. check all wiring connections ,make sure none are loose it will show up be paitent ,check voltage while pump is running shouldn't change.kirk
 
Is the GE controller a NEMA or IEC design?
Whats changed?
Have you megged the motor?
What does the motor drive, it may be driven load problem. The motor is dumb and will try to run the load regardless....
 
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