208V 3 PH TAPPING 3

[MCBOBRO]

I have a 208v 3 ph wye circuit w/ ground conductor. I am trying to use 2 phases to the inputs of the power supply that is rated for 170-264v input. I have 8 power supplies connect to various phases such as 3 supplies between phases 1-2 and 3 between 2-3 and 2 between 1-3. Only 3 of the 8 supplies work. I think I can not do this and need a neutral.
I think some of these are wokring beacuse of the same phase being connected to the same termainal of 2 suppies which then looks like the wye diagram with the loads connected to a phase and the senter connected together.
Any comments welcome thanks.

 

[wareagle]

MC
I am sure you know that the voltage to neutral from any of the phase conductors is 120 volts. You post says that the equipment is rated to operate at 208 volts. Can you determine what the difference is between the units that work and those that do not? Do you have an equipment grounding conductor install at each unit? Can you express you last sentence a little differently? I am not sure I understand.

 

[Jerry123]

Its sounds like your on the right track. Your load is a phase to phase load, 208volts. Spliting the eight supplies between the phases is a good idea.

I'll just add that since you load is phase to phase you will not need a neutral conductor. A equipment ground conductor you will need.

You also lost me on the last statement.

You can also use a voltmeter and to measure the voltage on the power terminals of the power supplies.

 

[jbartos]

Suggestion to MCBOBRO (Electrical) May 15, 2004 marked ///\\\
I have a 208v 3 ph wye circuit w/ ground conductor. I am trying to use 2 phases
///It is better to refer to "two phase conductor" since one phase will actually be applied.\\to the inputs of the power supply that is rated for 170-264v input. I have 8 power supplies connect to various phases such as 3 supplies between phases 1-2 and 3 between 2-3 and 2 between 1-3. Only 3 of the 8 supplies work. I think I can not do this and need a neutral.
///Yes, it may be done. The neutral will not be needed. However, the equipment ground should connect all conductive metallic surfaces.\\\
I think some of these are wokring beacuse of the same phase being connected to the same termainal of 2 suppies which then looks like the wye diagram with the loads connected to a phase and the senter connected together.
///Somewhat, but not quite. It will more likely be delta rather than wye since the wye has a neutral and delta does not. This is under an assumption that you will use all three phases, i.e. all three phase conductors. However, in case of arcing, your load may be damaged due to transient overvoltages since there will not be any system grounding.\\\

 

[MCBOBRO]

Thanks for the replies,
I just discovered this forum. I mostly do 24vcontrols and devicenet network layouts so power is not exacly my bag.
I am usnig a ground conductor to each enclosure. I am reading 208v at the power supplies that are not working. When I put a working power supply in the enclosure that is not working it works. Another piece of info I shipped three of the 8 supplies first and all these work. Then another 5 were sent which the installer said the package look a little rough and found the supplies rolling around in the enclosure. I don't think all 5 would be bad but I am be wrong. I am not really sure if it is a wye or delta panel it is a customers facilty and they provided 208v three phase with ground. I am not sure how to clarify my last statement but here is a basic idea of what i tried to accomplish. We are installing MPR conveyor 24vdc motorized powered roller There is a power supply every 20ft so instead of using 120 and making several drops I want to use 208v 3ph and connect up to 9 supllies per drop. the supplies are 24vdc @ 20A loaded about 80% so say 350VA plus .75 PF on 208 side. AB 1606-480ep series. I am using the Brad power cables to connect the 208 between boxes so all boxes are made the same.
Into box:
pin1 phase 1
pin2 phase 2
pin3 phase 3
pin4 gnd
out
pin1 phase 3
pin2 phase 1
pin3 phase 2
pin4 gnd

Ex phase 1 comes in to box 1 on pin 1 and phase 2 on pin 2 and leaves box 1 on pin 2 and pin 3 and phase 3 leaves box 1 on pin 1 of the connector. the power supply taps off of pin 1 and 2 for the 208 in each box this remains the same for each box. so the next box on pin 1 is phase 3 and and pin2 is phase 1. This should evenly distribute the power per phase.
Hopefully this helps give you a better picture.
Maybe this will explain how i think it is a y because of the swapping of phase in the enclosures it ties 2 power supplys together and they work. The three closest enclosures to the power drop work and it tees out from the drop so the first 2 enclosures are connected to phases 1-2.
If this is a y and i connect a power supply to 2 legs would it work? I don't think it would. it would need a neutral and i would only get 120v whcih I have done before in control enclosures. So if it does work which i think 1 is working that way it would be a delta and shoudll work for all.
I wish i could draw the circuit for you.
Thanks in advance,
Mcbobro

 

[peebee]

You don't need a neutral, as has been stated a couple times now. And it doesn't matter if your source system is wye or delta -- you will be connecting your supplies in delta, with no neutral, regardless.

Sounds like you have 5 busted supplies which were wired correctly but had internal defects. The beat up boxes were a hint. Swapping out a non-functional supply and having the new one work was the proof.

The only caveat I can think of here -- make SURE that your power supplies are not required to be wired line-to-neutral!!! Other than that, you should be OK with the wiring you've indicated.

 

[jbartos]

Suggestion: Since the schematic and possibly its variations are not possible to post, it would be better to prepare sketches and see an Electrical Engineering Firm, Electrical Professional Engineer or Consultant for a review of your sketches and concept. There might be circulating currents, harmonics, peaks, etc. that would definitely be better to be aware of or have them mitigated.