F
Frosty69
Hi people,
Just been out to a customer who is having problems with a motor. Basically it used to be fed from an old rerwireable db and for about three months it has been blowing the yellow phase about four times over that three months. The old db has now been changed for a wylex three phase db.
The problem
The motor is started and runs fine whilst in star for about five seconds then as soon as it switches over it pops the mcb, the motor is rated at 30kw and when load tested before the db was changed the highest readings were 50A at full speed. The motor is now protected by a 63A t/p type c circuit breaker.
The motor itself is about five years old and never serviced as its in a loft area in a factory that isnt very easily accessed.
All the electrical supply to the motor etc is fine so just wanted the opinion of somebody that works with motors on a regular basis.
I did the following calculations whilst I was there just to check loadings please let me know if im wrong.
1.732x400v=692.8A
30,000/692.8= 43.3A
43.3A/0.8= 54A
Any help would be greatly appreciated, I was going to try a 63A type D but I am worried that I will be spending money on materials that wont cure the original fault that was blowing the rewire able fuse?
They had a guy there today to check the motor and he says its fine although ive found out he never went up to the motor just checked the start stop unit and has told the company it is a loose connection in the new wylex db, which I checked before and the connections are as tight as a nuns!
Thanks
Just been out to a customer who is having problems with a motor. Basically it used to be fed from an old rerwireable db and for about three months it has been blowing the yellow phase about four times over that three months. The old db has now been changed for a wylex three phase db.
The problem
The motor is started and runs fine whilst in star for about five seconds then as soon as it switches over it pops the mcb, the motor is rated at 30kw and when load tested before the db was changed the highest readings were 50A at full speed. The motor is now protected by a 63A t/p type c circuit breaker.
The motor itself is about five years old and never serviced as its in a loft area in a factory that isnt very easily accessed.
All the electrical supply to the motor etc is fine so just wanted the opinion of somebody that works with motors on a regular basis.
I did the following calculations whilst I was there just to check loadings please let me know if im wrong.
1.732x400v=692.8A
30,000/692.8= 43.3A
43.3A/0.8= 54A
Any help would be greatly appreciated, I was going to try a 63A type D but I am worried that I will be spending money on materials that wont cure the original fault that was blowing the rewire able fuse?
They had a guy there today to check the motor and he says its fine although ive found out he never went up to the motor just checked the start stop unit and has told the company it is a loose connection in the new wylex db, which I checked before and the connections are as tight as a nuns!
Thanks