You are using an out of date browser. It may not display this or other websites correctly.
You should upgrade or use an alternative browser.
You should upgrade or use an alternative browser.
phase to groun fault in big motor.
- Thread starter sahafi
- Start date
- Status
- Not open for further replies.
friebel
Senior Member
- Location
- Pennsville, N.J.
Re: phase to groun fault in big motor.
To:sahafi, you say that you have a 1000 HP motor, 4160 volts, three-phase, and one phase is grounded.
No.1, I would like to see more details. What instrument did you use to check your motor, and what was the reading.
For example, I would check this motor with a megger, and I would use the 5000 volt scale.
Rule of thumb is: one megohm per each thousand volts. This means that that?I want to see at least four megohms to ground.
But, let me also clarify this statement, with that reading of four-megohms, I would allow the motor to run, but I would take the motor out of service as soon as possible and send to a motor shop for a cleaning and possibly a dip in the varnish tank.
Now, if you had been doing a preventive maintenance check of this motor with a megger on a routine basis, you would have been able to make a better decision of what to do.
To:sahafi, you say that you have a 1000 HP motor, 4160 volts, three-phase, and one phase is grounded.
No.1, I would like to see more details. What instrument did you use to check your motor, and what was the reading.
For example, I would check this motor with a megger, and I would use the 5000 volt scale.
Rule of thumb is: one megohm per each thousand volts. This means that that?I want to see at least four megohms to ground.
But, let me also clarify this statement, with that reading of four-megohms, I would allow the motor to run, but I would take the motor out of service as soon as possible and send to a motor shop for a cleaning and possibly a dip in the varnish tank.
Now, if you had been doing a preventive maintenance check of this motor with a megger on a routine basis, you would have been able to make a better decision of what to do.
Re: phase to groun fault in big motor.
Yes, Dear frieble I conducted a megger test by 5000V and I found 0.0 reading and as you know it is star connection winding so it may three phase to ground fault. just before the trip the relay reading recorder say the three phase were 1100amp while the normal reading is 186amp.
Yes, Dear frieble I conducted a megger test by 5000V and I found 0.0 reading and as you know it is star connection winding so it may three phase to ground fault. just before the trip the relay reading recorder say the three phase were 1100amp while the normal reading is 186amp.
friebel
Senior Member
- Location
- Pennsville, N.J.
Re: phase to groun fault in big motor.
To: sahafi: With the readings, that you just gave me, there does not sound like there is any doubt what needs to be done. It sounds like a rewind to me. As I mentioned in my previous thread, I am a big believer in PM,(preventive maintenance).
Taking megger readings on a routine basis and establishing a base line, you may have been able to prevent a rewind, which is certainly going to cost a great deal more than the cleaning and possible dip in the varnish tank.
To: sahafi: With the readings, that you just gave me, there does not sound like there is any doubt what needs to be done. It sounds like a rewind to me. As I mentioned in my previous thread, I am a big believer in PM,(preventive maintenance).
Taking megger readings on a routine basis and establishing a base line, you may have been able to prevent a rewind, which is certainly going to cost a great deal more than the cleaning and possible dip in the varnish tank.
- Status
- Not open for further replies.