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We have a situation where we have a long run of cable feeding some equipment.... the cable drop has reduced the voltage to approximately 510V 3p from 600V (fed from 13800VD - 600Y/347V 1000kVA dry type transformer with a 15A NGR). The equipment is having trouble 250HP)due to the drop and we...

What would be the output voltage of an two 600-120V PT's wired in open delta (b phase grounded) assuming balanced 600V 3p source? Would it be VAB = VCB = VCA = 120VAC or VAB = 120VAC, VCB = 120VAC, VCA = 1.73*120VAC...

Thanks Deltawhy and waross. I do have 150R fuses on the primary (slightly small but seem ok with the inrush points). However, I have received the damage curve from the manufacturer and the fuses protect the transformer ok mechanically however, the thermal portion is really unprotected. I...

To further explain I have read that in the US .... According to NEC® Article 408.36(D), individual protection for the panel-board must be provided on the secondary side of the transformer. The over-current protection device can be installed either ahead of or in the panel-board. However, I was...

To reword; are there any codes requiring a main over-current device be installed in (or in close proximity to) a panel-board regardless of the system supply?

Hello all, Situation: 75kVA 600V-240/120VAC 1P solidly grounded transformer with 200A fusible disconnect c/w TRS150R fuses on the primary, and a 400A 30CCt lighting panel on the secondary. Panel has main lugs only, 3x100A branch circuits, 1x60A branch circuit, 1x15A branch circuit. Items all...

"Hawk-IR" IR windows have been tested in arc resistant gear (or so says their literature). I believe they are owned by fluke now.

It was a simple enough question. I did not ever say that I was designing the system. Sorry for trying to learn a little something along the way. If anyone else feels that they have something to actually contribute it would be appreciated. Else - please keep your comments to your self, this...

Hello All, We have a new system that is fed from a single D-Y transformer. We are now adding an alternate source (a generator). We would like to resitance ground both sources. The questions is can this be done with one NGR? The suggestion was made to place a zigzag with NGR in the secondary...

Thanks Phovnanian....

Anyone have experience with mechanical lugs at 15kV? We have alot of gear with mechanical lugs that are 600V rated used at 15kV- most from along time ago....?

Hey Folks, Does anyone know why cable lugs have a voltage rating? Bare copper bus bars do not.... and that is all a lug is? I would assume it is for tracking distance to the insulation.... However, I am unclear as the use of 600V lugs at 15kV is common practice in industry. Regards, TULUM

Great thanks.

Thanks folks. The reason I asked is that it seems that (a) because the definition for the flash protection boundary itself does not directly mention that you must interact with the system for the PPE to be required (in the standards but not in the definition), most people are under the...

This has been discussed in the past - but the threads are now closed. We have many load centres (unit transformers) that have a HV switch with a dry type transformer and secondary distribution. As we are all aware the secondary transformer bus to the main breaker has a high arc flash...

Call the manufacturer of each piece of gear. They should have the answer.... otherwise start with the biggest heat loss items (such as transformers) and work your way down. Regards, TULUM

as alehman mentioned the 1000A/sq inch rule of thumb is just that a rule of thumb. If your a consultant taking a peak at some switchgear this rule is good..... if you are designing switchgear.... throw this rule out. Regards, TULUM

1.0 kVA/HP - Ind < 100 Hp and 0.8 PF Syn Motors 0.95 kVA/HP - Ind 100 < 999 Hp 0.90 kVA/HP - Ind > 1000 Hp 0.8 kVA/HP - Syn 1.0 PF

Have the contactor manufacturer size the fuses for the rating you are looking for.... most manufacturers have tested combinations they can supply. I have dealt with toshiba on this same issue many times. Regards, TULUM

Hello, I would like to make a PCB circuit that basically is a microchip controlled switch citcuit for a 5V 5.2A purely resistive load. The switch would be activated for 10Seconds maximum and would not have to be operated again for 60secs or more (could be days actually). Can typical PCB traces...