I said I would provide feedback to this thread. The problem was dual in nature. The motor controller would intermittently decide not to connect to Delta and stay in WYE which would cause overcurrent. Plus the rotor is damaged due to old age. It is easy to get a motor stator rewound but hard to...
I neglected to mention two things, there is a new Calco controller and new CT (all three phases have a CT). Someone, burned both out at the last attempt, reguards, and we have a old Calco man who is in charge of it. It is not timing or current. If the circuit breaker is set too low and has a lot...
Thanks PETRONILA, my expertise is with general industrial electrical maintenance but am the one who is called when the refrigeration motors act up. I think that this is due to the valuable assistance provided to me by this forum in the past. I will follow up on your suggestions and when the...
Motor is a Wye/Delta with contactor control. The fault is in the electrical and not the motor load. It intermittently has a problem when transfering from Wye to Delta where it makes a lot of noise and trips the local control 1000A circuit breaker. Motor FLA is 560A. Voltage 480VAC. RPM is 3570...
What side bands do I look for when analyzing a 3600RPM 500HP 480V refrigeration motor. The problem is intermittent but it is an old motor which has been rebuilt at least three times.
Firing angle is determined by which type of coordinates you are using. You have a square which is the most accurate, it is called right angle geometry. Then is that fails you have what is called Coordinate geometry which is two angles and side or two sides and an angle. And if that fails you...
Again I am educated at this forum. I did not know what a vacuum contactor was before. Does not the NEC cover this about a physically lockable disconnect on the motor branch circuit? The user's engineer you mentioned must be right out of an electrical correspondence school and had someone else do...
Question: A 12 wire 500HP refregeration motor which is labeled wye/delta and is really a wyewye/deltadelta motor, once seven seconds have passed and the electronics has determined that there is nothing wrong with the motor it adavnces to deltadelta with a phase reversal. Does the phase reversal...
I thought I would critique the ex-problem I described. The solution was accomplished due to present and past forum responses and it was something I did not anticipate. On larger motors i.e. 400HP and above which are high speed i.e. 3700RPM and the bearings and the stator have been replaced, then...
It has been my experience with three phase motors that when you have two phases pulling close to the same current and one pulling 25% lower then I look for a poor connection either at the peckerhead or the parts feeding the motor. A poor motor starter contact or bucket contact could cause this...
Thanks for the input. I was looking for theoretical answers which you provided. To the meat of the problem. The motor is protected by monitoring all three phases with its seperate circuit. The motor drives a screw compressor. The ammonia screw compressor electronics only monitors one phase...
I think that you all missed my original question. If a motor is pulling 520A on phase A and 550A on phase B and 570A on phase C. What is the average current?
I am having trouble understanding the current of a three phase motor. Say I have a 500HP Y/D refrigeration motor with overload protection. The overload protection is sensed by T1. T1 pulls 520A, T2 pulls 550A and T3 pulls 570A at full load. FLA=570A, 460V with a service factor of 1.5. It seems...
Thanks so much for the info. Either ex post or ipso would apply. Ex post a little more than ipso. We were in a contract where the rules changed all the time. Thanks again, Bob
Sirs, I am going to ask a question which has been bugging me for a long time. Since I have seen Latin used on this post and I could not find a Lawyer's forum, I thought I would give it a try. What is "Expo Facto Law"? I have found that it means "after the fact". This definition is incomplete...
Sirs, Now I am as confused as if I tried to digest the NEC book. The only logical answer I have is that it would be generally prohibited unless UL approved, even though my idea would be structurally and electrically safe.
Thank you all for you input. As to the last responder, when you order the HID lamp assembly, the way I described, this is the way it comes from the factory and the way I have seen it commonly used. The rigid conduit supports the HID lamp fixture. Of course I will always use the NEC code. I wrote...
I did not think that rigid conduit could be used to support anything. How about the HID lights. They are designed to be supported from 3/4" conduit. There is a 3/4" threaded J-box at the top of the ballast where the conduit is to be screwed into and then suspended from the ceiling. The J-box is...
Sirs, I have some long tubular flourscent light fixtures which I need to hang in a difficult area. I have an idea which through a prototype works fine. I have ran 3/4" conduit which is supported by I beams every six feet. I suspended a 100" tubular light fixture from the conduit. This fixture is...
