Becareful with the Hipot as it does stress the insulation and you could pop it. I would start low and work up. I am not in the office at the moment but If you have the PI test results and they look good are you comparing with previous results? 500v DC is like 1000v AC as the electrical stresses...
It looks like you have a brake in your circuit. Look at break wear. The inertia, may have the motor still turning when you change direction. This will cause high current.
I have never tried the Steinmetz connection. I have used the capacitor method but the motor did run hot as it is very inefficient. Here are my notes.
Welcome to the forum. Lots to learn and nice people. I hope to emulate you. Well done. My dad was born in 1919. Survived WW2 and then was...
Sometimes dirt on the pole faces or even rust can cause a chatter but my money is on the fact that it did not fully close. If the former, wipe a small amount of oil across the face with your finger. Also the use of VPCI in the panel would assist to prevent this.
There is a tendancy to move to...
If your access to the circuit is via the power side, you can still run your relay into the power circuit and limit the power relay via your limit switches. You will have to watch the overshoot from the inertia. The activation section may have to be extended to cover the overshoot or it may start...
Hi Sibeen, My English! The inverter has a 400v, 4 wire primary, from a star transformer, 11 000v to 400v, 2 000kVA, DYn11. The primary of the inverter / UPS is indipendant to the output. The inverter runs all the time. It converts the 400v AC to DC on a bus which charges teh Battery backup...
What changed? Has someone laid a new cable or wires near the metering wires? Have you lost the earth screen on the power cables with a bad gland connection. Looking at the imbalnace it is 0.1% That is very small. 40v on a 400v system. Have you lost your reference earth and thus your neutral...
Dear Sibeen, Sorry I travel ad have been away in Swaziland where this problem exists. The transformer feeds into the UPS. Yes the star point is earthed. The UPS runs a system where it charges a DC bus which is then chopped up into three phase AC so the primary and secondary sides of the UPS are...
At an installation there is a 400v, 50Hz, 3 ph,4wire, DB with a Fault Level of 35kA. It is fed from a 1MVA, 11kV to 400v, DYn11 trf. This DB feeds a 40kVA, three phase, UPS device. In the Main DB the breaker feeding the UPS is a 125A thermal magnetic MCB set at the correct levels. No earth...
Dear MasudDU,
I totally agree with Mark about the torque issue if it was wound to be a 400v Delta and you wish to run it in star. I would ask the motor rewind company for their rewind data sheets. They may not mean much to you but if they don’t supply them quickly then there may be some...
Close up of the shaft after they did some polishing. This is what started my investigation on this one.http://files.engineering.com/getfile.aspx?folder=4b82f7a8-52cf-40da-81e5-aa51ae5a5f4b&file=picture_164.jpg
Going for two this time. Top bearing frosting and shaft damage.http://files.engineering.com/getfile.aspx?folder=2d66afb3-5332-4772-b8f1-dcb821884936&file=mvc-006s.jpg
Thrust bearings. This is not a mechanical issue.http://files.engineering.com/getfile.aspx?folder=70872c88-4963-4c18-9309-422d261187e0&file=mvc-005s.jpg
We have had much greater voltages. You should only insulate one side to stop the circulating currents. If you insulate both, as you say, the voltage will build up from static electricity. Now there is only a thin film of lubricating oil electrically insulating your shaft from the ground of the...
If you can’t find the exact transformer voltages look for one with the correct insulation and then the correct turns ratio. If not a more expensive option to run two transformers in series with the correct final output. Depends how desperate you are.
Now I climbed out of the box for this one...
For protection and tripping we look to the AVR. Our preferred AVR has two additional settings. Very high for up to 10 seconds and high up to 120 seconds. The rating is a percentage of the defined excitation current. The high allows you to start the large motor etc., so it will boost the...
[bigsmile]me again. The Siemens document is perfect. Thank you electricpete. I quote.
In the preferred situation, the power factor correction capacitors are sized at or below 90 percent of the no-load kVAR
requirement of the motor. If the capacitors are too large, the motor can be subjected to...
Sorry. I took Warross's comment to mean that he had applied full correction to a motor and that it survived. It only becomes a problem on light load when the kVAr vector drops. In a normal installation, equipment runs flat out and light loads are uncommon. If you are running a light load and...
