We went into a bldg yesterday for a show. Our 3 phase chain motor controller did not work. We pulled another one and it did not work either, although they both have worked since day one. Voltage in the building was 130 per leg. Ended up getting a generator and everything is fine. Anyone know if that voltage is too high. Or, is there a possibility that the transformer supplying the service to the disconnect could have been single phase and could have sent two legs split at disconnect and one leg straight? Trying to figure if this is a bldg problem or our issue. Thanks
3 phase chain motors
- Thread starternewdaypro
- Start date
One of the crew just metered at the disconnect. 225 across each of the three hot legs.
Yes. 223-225 between each pair. Yes, 129-130 between each hot and n/g. Our feeling is that even though there are three hot legs, it is not necessarily three phase.
Well the meter doesn't lie (well, theres some things a standard meter might not detect properly). Three phase has the legs rotated 120 degrees, single 180 degrees. As there are only 360 degrees possible, theres a limit to the options for "wrong". If it were not three phase, I think you would see differences in the hot-hot voltage between different pairs. I guess you could have something like four-phase (don't think it exists, but could probably be created), but then your hot-hot voltages would be lower than normal, not higher. With less than three phases you wouldn't have the hot-hot voltage between all 3 pairs...
130*(Sqrt 3) = 225.
You do have three phase power. Now why your motor controller didn't work with the building power I have no clue. What brand and model were the hoists and controller?
EDIT: Do you have a meter that can measure the frequency of the source, weather it is 50Hz or 60 Hz? I'm thinking that you may have a slightly hot 127/220V 50Hz Feed, now how or why that was installed if it was is another question that I can't answer.
You do have three phase power. Now why your motor controller didn't work with the building power I have no clue. What brand and model were the hoists and controller?
EDIT: Do you have a meter that can measure the frequency of the source, weather it is 50Hz or 60 Hz? I'm thinking that you may have a slightly hot 127/220V 50Hz Feed, now how or why that was installed if it was is another question that I can't answer.
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David Ashton
Well-Known Member
may just be that your controller has over-voltage protection built in, I had a similar issue with some dimmers which had this protection.
For a few years, I traveled with an ice show where I built the ice rinks on stage. Our chiller required 3 phase power and had a built in phase detector. At one venue, I got 120 from each phase to neutral, on all three connections (cam locks), but the phase detector switch would not set. Finally I discovered that the camlok tails were wired with two of them on the same phase. When I brought this to the attention of the tech director, his comment was that they had never had a problem in the past.
On further discussion, I found out that they had only ever tied in audio or lighting. In these cases all of the devices were only looking for 120 to neutral on each of the three connections, and didn't care about the phase relationship. I pointed out that wired that way, they were over loading the neutral.
When I asked for them to correct it, so that my chiller would work, they were quite offended. I had to show them in the Rider that I could walk away from the venue if not provided with proper power, and the loss of revenue from a cancelled show would be on them. They let me correct it, I think because they didn't have an electrician who understood 3 phase power.
When I went back the next year there was a bit more cooperation.
On further discussion, I found out that they had only ever tied in audio or lighting. In these cases all of the devices were only looking for 120 to neutral on each of the three connections, and didn't care about the phase relationship. I pointed out that wired that way, they were over loading the neutral.
When I asked for them to correct it, so that my chiller would work, they were quite offended. I had to show them in the Rider that I could walk away from the venue if not provided with proper power, and the loss of revenue from a cancelled show would be on them. They let me correct it, I think because they didn't have an electrician who understood 3 phase power.
When I went back the next year there was a bit more cooperation.
BillConnerFASTC
Well-Known Member
When lamps use to all be 120 volts and dimmers always dropped 5-10 volts across the choke and then 100-200 ft of voltage drop, transformers were tapped up. Explains voltage maybe, not why controller doesn't work. Vintage of building?
You're comment is an exact, to the letter, duplication of what we've been through and what we feel the issue is. We could be wrong but want to get it fixed because this is a multi year contract in this venue.
Btw...our controller is a Sjonberg and other is a motion lab. The phase connector light on the motion lab does not light up which had us changing our thoughts in the issue.
Btw...our controller is a Sjonberg and other is a motion lab. The phase connector light on the motion lab does not light up which had us changing our thoughts in the issue.
Jay Ashworth
Well-Known Member
JD
Well-Known Member
As stated prior, 225 would be the correct H-H-H voltage for Wye if the line voltage was 130. Power companies have been creeping up the voltage for years. In our area, norm is about 127 H-N which is only 3 volts lower. Hard to imagine overvoltage protection kicking in at 130, (or 225 H-H) but stranger things have happened. I don't know of any reports of motor kick-offs in the Philly PA area, and we often touch 130. Assigning fault is going to be tricky, but bottom line is they worked on the Gene, so I would stick tight to that subject.
If you suspect two phases are actually one phase which has been bussed out to two "legs", a thorough metering should reveal the problem. Metering X-N, Y-N, and Z-N, as well as X-G, Y-G, and Z-G, you should find ~120V in all cases. Then when you meter X-Y, Y-Z, and X-Z, one of those measurements should come up as 0V, while the others come up as ~225V or so. If you find 0V between any of the hot legs, you know you're not getting the 3-phase power you're shopping for. If that all checks out, I'd further investigate any over-voltage protection mechanisms. Easiest way to pursue this is to give Motion Labs a call and inquire as to what reasons their product wouldn't have some or all of indicator lights fire up after being connected to what appears to be an appropriate power source. If the Motion Labs st
Thanks to all for your help. I have been thoroughly schooled on this issue by many experts. I really appreciate your time. Since we're on the gene everything is running great. However the video group is using bldg power and getting faults on all their gear and power protectors (Unfortunately the gene is not running 24/7 for their editing purposes). Not sure what is going on but we will survive it and deal with it for next year. Not too worried about gene cost/responsibility as all our gear will come out alive.
