Having a moment with motor rotation

Dsg319 said:
What is the purpose of bringing in power CCW vs standard CW supply?
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The parasitic vibrations of three phase cable runs can cause screws to loosen if the phase rotation is backward.

Seriously, I can think of no inherent benefit of CCW vs CW, so the only reason is to maintain consistency with previously installed equipment.

Getting rotation wrong can break stuff, so having an _arbitrary_ standard that you can point to and say 'this is the way it should be under my roof' is useful. Think about screw threading: it is rarely the case that left handed vs right handed screws matter, but we arbitrarily pick right handed screws as the standard way to make them.
 
Dsg319 said:
Funny thing about this. Permanent power supply at this place is a natural gas capstone generator.

The generator was clockwise.
Customer (engineers at the company) like their power to be brought into the facility counter clock wise.

Result. All 9 three phase motors on site had to have phases swapped.

What is the purpose of bringing in power CCW vs standard CW supply?
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Standard rotation where I am CCW from the utility so standard is whatever someone wants it to be. I dont know what it is in Great Britain but I'm sure Besoker will tell us it's simpler.
 
ActionDave said:
Standard rotation where I am CCW from the utility so standard is whatever someone wants it to be. I dont know what it is in Great Britain but I'm sure Besoker will tell us it's simpler.
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Alls I know is if they would have left it alone I would have had to change rotation on 2 motors vs the now 11 lol
 
ActionDave said:
Standard rotation where I am CCW from the utility so standard is whatever someone wants it to be. I dont know what it is in Great Britain but I'm sure Besoker will tell us it's simpler.
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Apparently they are as confused as the rest of us :)

The Liverpool Cross

Power Engineering Consultants Plc, Power System Protection Specialists
www.pecplc.com www.pecplc.com
 
winnie said:
I regularly work with 'high phase order' experimental systems (more than 3 phases). Your choices are CW, CCW, or WTF.
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You can get that third thing with basic single or three phase dual voltage motors if you get say just one winding connected in wrong polarity.
 
kwired said:
Can't say I ever encountered a VFD with bypass, but seems you would need to verify rotation of input as well as output so that it won't want to reverse when the bypass is activated. seems would need to also be either more complex transition or at least an open transition between the drive output and the bypass mode to assure there is no phasing differential being applied simultaneously, which the drive itself probably will not like at all.
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All of the many VFD'S with bypass have at least auxiliary contacts on the M2 drive output contactors & the M3 bypass contactor. This prevents both coils from being energised at the same time. Best is when drive manufacturers combine the interlocking contacts along with side by side contactors with an arm that prevents both contactors from being pulled in at the same time ( like the ones on reversing starters ). Drives we had all had what was called flying start that came in handy during monthly testing of over 75 large ATS switches. If I had a motor running on bypass while working on a drive would turn the selector switch to off for at second or two then turn on drive and usually within a few seconds drive was capable of auto restart and perform a flying start. ( flying start matches the current speed of motor ) On the numerous 60 to 125 HP air handlers ( two per system ) and a return fan all of the return fans had drive bypass and most dual motor supply fans had bypasses. Even had JCI have most handlers be able to open certain return & supply cross over dampers to supply air if both supply fans were down.
 
Dsg319 said:
Funny thing about this. Permanent power supply at this place is a natural gas capstone generator.

The generator was clockwise.
Customer (engineers at the company) like their power to be brought into the facility counter clock wise.

Result. All 9 three phase motors on site had to have phases swapped.

What is the purpose of bringing in power CCW vs standard CW supply?
Click to expand...
Should not matter. At the large progressive hospital that I retired from when we had to back feed a 100 to 400 amp panel that was feed from a different electrical riser we would have to use a rotation meter on the 480 wires even though all were marked BOY ( Brown orange & yellow ) a lot of times they were opposite rotation. Same with 120/208 volt panels. In newest building all panels on the 12 floors with over 150 panels ( normal & emergency ) power appeared to all be phased out the same but still checked with phase rotation meter before back feeding.
 
garbo said:
Should not matter. At the large progressive hospital that I retired from when we had to back feed a 100 to 400 amp panel that was feed from a different electrical riser we would have to use a rotation meter on the 480 wires even though all were marked BOY ( Brown orange & yellow ) a lot of times they were opposite rotation. Same with 120/208 volt panels. In newest building all panels on the 12 floors with over 150 panels ( normal & emergency ) power appeared to all be phased out the same but still checked with phase rotation meter before back feeding.
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Several years ago at a cattle feeding operation I frequently did work for they had three different services at different locations on the place. One was at a far end and was pole top transformers but had aging underground primary conductors running to it. (poco owned/maintained) It was originally full delta and had three coaxial type MV cables. The load was minimal enough at some point this basically became open delta system, and when a fault occurred in a cable (it was getting near needing replaced altogether) they just would swap the bad one with the spare, of course they needed to double check proper configuration of secondary. One the last times it failed before they finally replaced the cables the guys put rotation meter on secondary and confirmed rotation, but neglected to make sure high leg was in the correct position. A majority of the load other than a three phase well that wasn't effected was pole top lights in the feed yard and tank heaters in the cattle water tanks. I replaced quite a few pole lights after that incident. POCO paid me since it was their fault. Bad thing is I had recently went through most of the place and fixed any that were not working not long before this happened which was somewhat of an annual thing to do. I know I replaced a few that were replaced not so long before. This was back when HID luminaires were the norm for something like this and these were all mercury vapor type.
 
Here in Northern Calif., PG&Es system is ACB, a fact that seems to baffle all sorts of people for some reason. For short a while in the 90s, a company I worked for made a solid state motor protector product with phase monitoring built-in, but it only looked for ABC, no way to change that. That was “fun” for about 6 months until I got them to add a freaking switch…
 
Jraef said:
Here in Northern Calif., PG&Es system is ACB, a fact that seems to baffle all sorts of people for some reason. For short a while in the 90s, a company I worked for made a solid state motor protector product with phase monitoring built-in, but it only looked for ABC, no way to change that. That was “fun” for about 6 months until I got them to add a freaking switch…
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ACB is someone's actual designation. They could still arrange the same leads as CBA and it still has same rotation. High leg where applicable ends up on a different bus is really about the only thing that maybe matters with this to the user. A simple three phase motor could care less what you call any of the input leads all that matters is the rotational sequence.
 
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