10HP 3Phase Elec. Motor Problem

[Ed Carr]

Went on a call today.Problem, 480 volt motor was wired wrong at the
magnetic starter.The coil was separately fed from a 240 volt source
but the jumper from the motor suuply voltage was not removed.
Apparently the motor was being fed 120 volt on one leg(I think).
I rewired the starter and checked for proper voltage at the motor
safety switch,480 volt.When I closed the switch loud hum from motor
and lost my 480 volt.I then opened the p-head on the motor and
found it had been configured to 440 volts but the jumpers had not been
removed.I removed the jumpers closed the switch the motor started to
run but then tripped the breaker again.The 480 volts are supplied by a generator
while the 120/240 single phase is the utility.Thats how the motor was getting fed
from the starter.The nameplate rating is 15amps at 440 volt and I am feeding
it through a 20 amp breaker.A long post I know,where do I go from here?
Do you think the motor was damaged and how can I tell if it was?

Ed

 

[JacksonburgFarmer]

Do I understand this right???
You have a single phase 120/240 service
You have a 480V 3phase motor
You have a Rotary Phase Convertor to run the 3 Phase motor
System (motor and starter) is operating on 480V

Questions.....from me to you.....
Where are you deriving 480V from??? Your phase convertor will supply the same voltage as its input.....240V

Do you have a transformer in this setup???

I belive here is what you have....240V convertor feeding a 240/480 motor. If this is so.....Hook your motor up 240v, and it should run....do you have a megger to test the motor with????

 

[Besoeker]

Do you think the motor was damaged and how can I tell if it was?

Ed

If the motor smoked and smells bad, it is a very distinctive smell, then it is most likely to have been damaged. Otherwise, possibly or even probably not.
Check the winding resistance and insulation to ground.
And 480V on a 440V motor is a bit high.

Without any further information, it is difficult to comment on your circuit arrangement.

 

[growler]

The coil was separately fed from a 240 volt sourcebut the jumper from the motor supply voltage was not removed.
Apparently the motor was being fed 120 volt on one leg(I think).
I rewired the starter and checked for proper voltage at the motor
safety switch,480 volt.When I closed the switch loud hum from motor
and lost my 480 volt.

You really have to be carefull working on motors out there in the field. It's not that they are all that complicated but the fact that before you get there everyone and his brother may have been tinkering with it.

The first thing is to never try to start a motor until you have checked all connections and make sure it's wired correctly. Then you ask just who all has been working on it and sometimes they will tell you and even the disasterous results they had. Then check out the motor to see if they smoked it while tinkering with it. People will try to blame you for a motor that they fried earlier so don't even try to start until everything has been checked.

With your problem I would take the motor leads loose at the motor and make sure that when the motor starter is engaged that you do in fact have the proper voltage comming to the motor. If one leg is missing it will single phase and draw more power and will also burn the motor up. If the voltage is correct there is nothing but the motor left so check for either a shorted winding or an open winding. If you don't find anything wrong then try to start and use an ammeter to judge current draw.

 

[Ed Carr]

Guys, thanks for your help.The motor did smell burned
and further testing found found continuity from line
side of connections to ground.I am taking it to a local
repair shop in the morning.Hope the fix isn't too pricy
as I'm afraid it was one of my guys that did the damage.
Glad it's Friday!

Ed