Recent content by unclebob

You need a zigzag transformer that will provide you a neutral that you will connect through a grounding resistor. The size of this resistor will determinate the size of the zz transformer.

As the project manager couldn't find anything wrong with the motor or the distribution system, he decided to replace the VFD. His company has several across the country, so they'll try another one.

Adding more details here: Motor has been tested and is in good shape. The drive however is burning parts on the control board: MOV, capacitors.... The newer drive installed 2 weeks ago is already showing signs of burning. Application is using 47 Hz, its not at full speed. I've been asked to...

I would use, at a minimum, a 12-pulse drive.

What happens if you try to use a 500 hp motor, rated at 440 V , with a 6-pulse drive, rated at 600 A?

Along with the currents readings, can you show us the phase angles of said currents?

There are times when you have to re-use your old laptop with Windows98 installed and a DB9 connector.

Field testing of some Eaton closed transition ATS's gave paralleling delays in 80-90 msec time window. An alarm is set at 100 msec that stops the process, if need be.

You would have to disconnect all 3 coils at neutral ends. At this power, these should be welded.

You could add a piece of bus bar with the required holes for the CT and for the lugs.

A_B_C_A_B_C_N_N _C_A_B_C_A_B_N_N A_B_C_N That looks good? Found that too... http://www.advcablebus.com/downloads/advancedcablebuscatalog.pdf

DSP MKII is a ground fault relay. It comes with a grounding resistor. It's the vintage model of the I-gard. If you have feeder modules, it will tell you which phase is grounded and on which feeder. It leaves you live with one occurring ground fault (Alarm). If you get a second ground fault on a...

67 V where? Power supply? Check fuses.

This SDP module should be installed right into the switchgear. 8 feet distance is too large and protection is lost. Our manufacturer states a max cable length of 14 in! And we use 30 A breakers. Not much current flows into this, only high voltage transient surges.

Fault current will use all provided ground paths to return to its source, the A Trafo, assuming it's secondary is wye and the neutral is grounded.