Recent content by Live2learn

Just I thought when I layout HRG low voltage systems I recommend (sometimes)the use of 2kV conductor to deal with the overvoltages. Anybody else do this?

This reference is 20 years older than me. From the industrial power systems data book by GE Dec 21, 1964. Table one on page 1 .32 has a sable 460 v charging current 3Ico - amps/1000kVA of system capacity to be around .1-2.0. that is without andy contribution from surge protective capacitors...

Just checked it. It was the frequency variance. Thanks

I am about to do a load transfer on a UPS and I noticed a "Static Switch Unable" alarm on an old Emerson UPS. I believe we also get alarms on the newer Liebert UPS ("Not OK to Transfer"). I would like to understand why this is happening. When the generators that support the Emerson & Liebert...

yeah it was in the manufactureres instructions and I typically spec ABB so it was probably them.

any problems in particular? I had to remove a screw when I installed my VFD's on an ungrounded delta.

So it is rated for 12kA symetrical with the DC offset and utilizing the x/r ratio we come to 20kA (make and latch). I know LVPCB can have a multiplication factor of up to 1.26 with and 20 x/r ratio and a 5% pf, so does that mean in medium voltage systems it can have a multiplication factor of...

I have attached a Vacuum Interrupter Name plate specs. Type: PM, Style: VSA, BIL: 95kV, Phase: 3, Max Design Volt:15.5, Continuous Current 600A, Interrupt Rating: 12,000A, MOMENTARY (10 CYC.): 40,000A, Make and Latch: 20,000A, Mfr Dat: 1994, Interrupting time: 3 cycles, Weight: 2100 lbs...

yes I do believe you may use that chart only if they are for those circuit breakers listed in those combinations. For your westinghouse circuit breakers I would get in touch with the manufacture to get a hold of the necessary information.

I do not think current limiting fuses will get you there. You also can not ride the fuse curves for current limiting capability. I guess you can if you REALLY have to, but the dynamics of breakers opening and the fuse reaction to it has to be tested and confirmed. That is why when series...

yes xfmr was meant to be transfer - sorry 1. but the service entrance transfer switch is 4 pole with permenant generators and utility 2. the downstream switch has two connections from different swbds within the facility. the 4 pole switch feeds a 3 pole switches with L-N loads. so I have 4...

xfmr switch should have read transfer switch. the two sources for the three pole downstream switch are a portable 4 pole generator transfer switch and a normal source the normal source which is upstream has the 4 pole transfer switch with the utility and permenant generators. so a 4 pole...

I have a system where the generators are a seperatly derived system and the utilty feeds the normal and generator the emergency. From the xfmr switch for a number of reasons it feeds another transfer switch. (all loads are have are 4w+g) So the long and short in a 4W+G system can a four pole...

I have a 4w+G system in which generators and utility feed a common 3P automatic transfer switch. The load then goes to a 3w+G switchboard and then to another 3P transfer switch. The utility is 2000kVA OA, 12470 pri Y 480/277v sec and the Generators are connected Y through a 3 pole transfer...

In my industrial plant I have (4) 480V 4W+G 2000kW .8pf generators that all terminate in paralleling switchgear. From the switchgear we go to closed transition switches and that feeds the loads. Question: I went through the shop drawings which are about 2 years old and noticed know bus...