Utility High Leg, Open Delta Phase Converter, and a Motor That Can't Use Either

[ptonsparky]

@ $85,000 the owner can afford the proper arrangement for power source.

 

[tortuga]

. If it wasn't an $85,000 saw

Is it new? Can you post a link to the saw?
There is a 'universal' equipment design standard for the Americas thats settled on 220Y/127
If its new equipment for the North and South Americas market I'd bet a milkshake its 220Y/127
I have had to correct sales people whom refer to this as the imaginary 240Y120 LOL

Equipment labeled 220Y/127 *should* tolerate our 208Y/120 - 240Y/139, even 240 dleta unless it has a VFD internally may not tolerate a open delta as discussed in many old threads.
I would just call and ask your local POCO if there are 3-primaries on the pole to convert the service to 208Y/120.
It may not be possible as 240 open delta is often used where there is not a 3rd primary leg.
Than again I have run across some POCO's that will upgrade old open delta banks for free as it benefits their system somehow to not have them, not sure why this is but there are old thread on here about that also.
If this is a single customer on the transformer bank the POCO may even notch up the tap change 5% for any old 240 motors in the shop, then your at 218Y/126 under full load (fully within spec of 240V )

 

[Hv&Lv]

Not entirely certain that it requires a fully balanced system, but certainly it needs 240V phase to phase and 120V phase to ground max.

This definitely helps fill some of the knowledge gap. Is there no delta configuration in 3 phase that gives 120V to ground on all three legs?

Can you post a picture of the data plate? That would clear up so much confusion.

I’m not understanding why you need all three legs to have 120 to ground either.

 

[Little Bill]

I hooked up a large planner that was 3ph. The specs said if the utility service was Delta with a high leg, or a RPC was used, not to put the high, or mfg, leg on a certain terminal. That terminal obviously was for 120V to neutral/ground.
I would bet the OP's saw is the same way. Just don't put the high leg on the 120V portion of the saw. Other than the 120V portion, the 3ph, 240V portion of the saw would have no idea, or care, that a high leg was being used. All three legs would be 240V line to line.

 

[C4ctus99]

That is physically impossible.

In a balanced system you either get 208V phase to phase and 120V phase to ground, or you get 240V phase to phase and 139V phase to ground.

Another portion of my knowledge gap... I have a basic understanding of transformers but never have had the opportunity to learn about all the different variations and how it affects the voltages.

If this is true, your only choice to use one the previously mentioned wye transformers 240Y/139V (look for a drive isolation transformer) or a 208Y/120V ( a standard transformer but it won't provide 240V).

My guess is that you are not dealing with actual engineering support. The engineering department probably has some suggested method rather than a simple don't do it. The saw is much more than a simply motor, it likely contains several filters for multiple drives and electronics.

My assumption was that it needed to be closer to 120V since they say not to use a high leg. I finally got a sparse schematic from them today and it is originally European (made in Italy), nameplate is 480V, schematics say 400V to motor @50htz. The technician I talked to has some reference material that he did not send me that states "no high leg" and he said a senior engineer told him 245V max for the motor... so I may have another issue as our utilities like to run 245-249V

 

[C4ctus99]

Can you post a picture of the data plate? That would clear up so much confusion.

I’m not understanding why you need all three legs to have 120 to ground either.

The nameplate is incorrect for the machine, they manufacture for 480Y then ship to US and rewire for 240V Delta. Unfortunately they did not swap out tags so I am stuck with the wrong ones. I assumed 120 to ground since they specified no high leg, but must be incorrect.

I would bet the OP's saw is the same way. Just don't put the high leg on the 120V portion of the saw. Other than the 120V portion, the 3ph, 240V portion of the saw would have no idea, or care, that a high leg was being used. All three legs would be 240V line to line.

I assumed the same but the technician said that it specifically stated no high leg for motor.

 

[C4ctus99]

@ $85,000 the owner can afford the proper arrangement for power source.

I've tried a couple times... going to end up costing him more trying to piecemeal it but that is his decision.

Is it new? Can you post a link to the saw?
There is a 'universal' equipment design standard for the Americas thats settled on 220Y/127
If its new equipment for the North and South Americas market I'd bet a milkshake its 220Y/127
I have had to correct sales people whom refer to this as the imaginary 240Y120 LOL

That may very well be what it is... It is an FOM USA Panda 550 upcut saw. No documentation or paperwork on their website I could find and very frustrating. Brand new equipment

Equipment labeled 220Y/127 *should* tolerate our 208Y/120 - 240Y/139, even 240 dleta unless it has a VFD internally may not tolerate a open delta as discussed in many old threads.
I would just call and ask your local POCO if there are 3-primaries on the pole to convert the service to 208Y/120.

Biggest problem is that the high leg is downsized and the service entrance equipment is at least 30 years old. I have tried to convince them two or three times now to just replace the service but I am too nice a guy and like to give people options. The technician did state that the power supply is 220V so it could very well be the case.

 

[C4ctus99]

Here are two screen grabs of the specs he sent me for reference. Everything else is control circuit diagrams. I am going to ask him about the paperwork that says no high leg on the motor. Motor comes from the factor as 400V Wye with a 400V power supply, however nameplate says 480V 3 Phase. it gets rewired to 230V Closed Delta and the power supply gets replaced with a 220V power supply. (Power supply is the term used by the technician)

Maybe the power supplies convert the 480/230 to 400/220 for the motor? And maybe the high leg would mess with the 220V supply?

 

[hillbilly1]

Another portion of my knowledge gap... I have a basic understanding of transformers but never have had the opportunity to learn about all the different variations and how it affects the voltages.

My assumption was that it needed to be closer to 120V since they say not to use a high leg. I finally got a sparse schematic from them today and it is originally European (made in Italy), nameplate is 480V, schematics say 400V to motor @50htz. The technician I talked to has some reference material that he did not send me that states "no high leg" and he said a senior engineer told him 245V max for the motor... so I may have another issue as our utilities like to run 245-249V

The Italians do not rewire their machines for American voltages, you have to get them to send the correct auto transformer for the machine voltages. I have several Italian made CNC machines with 240 delta feeding them, and had to make them send a transformer with it.

 

[C4ctus99]

The Italians do not rewire their machines for American voltages, you have to get them to send the correct auto transformer for the machine voltages. I have several Italian made CNC machines with 240 delta feeding them, and had to make them send a transformer with it.

Initially that is what I thought a week ago however the machine gets rewired in the US. Power supply gets swapped out, a control module gets replaced, and the motor gets rewired from Wye to Delta, I have talked with the technician who did it on the exact machine I am now trying to power up.

 

[jim dungar]

Our industry slang often gets in the way of finding solutions.

Many, but not all, high-leg delta services are created from open-delta transformers. These transformers often result in poor voltage regulation especially on the B-phase. This poor voltage regulation messes with electronics, so many technical service people say "No high-leg sources, when they really mean no open-deltas".

My guess is you will want a 240V closed delta, but I would recommend the 240Y/139 as it gives you the chance to have a grounded secondary.

 

[MTW]

A bit more about what it is. Designed for a 400V Wye, no clue what the vendor did for the conversion.

 

[MTW]

Seems to me that conversion to 480 V wye, @ 60Hz would have been the most practical choice.
The motor will run fine at that. What needs to be done with the control power is unknown.
That's a standard voltage transformer output here. What is unknown is if the site has an open delta service or not.
That could be an issue with voltage stability, depending on service size and other loads connected to the same service transformer bank.
Do you know if the service is supplied open delta ( two transformer pots instead of three) and what size is the service that they have existing ?

 

[winnie]

Ok, that _motor_ (not the machine, just the motor in the machine) is designed with 3 230V 50Hz coils. If those coils are connected in the delta configuration, then the motor requires 230V 50Hz 3 phase power. If the same coils are connected in the star configuration (another word for wye), then the motor requires 400V 50Hz 3 phase power.

The screenshots all say 50Hz. The .pdf sheet gives 50Hz or 60Hz values, but only a 50Hz speed. There may be a VFD/frequency converter involved, but if not then the saw will operate at higher speed on 60Hz. A 50 Hz 2800 RPM motor will spin at about 3360 RPM on 60 Hz.

If the motor is fed by a VFD, or there is frequency conversion involved, then the prohibition on the high leg makes sense. If the motor is directly connected to the incoming 3 phase supply, then it should work correctly with a high leg system.

 

[hillbilly1]

That may very well be what it is... It is an FOM USA Panda 550 upcut saw. No documentation or paperwork on their website I could find and very frustrating. Brand new equipment

Sounds like the Italians are selling the customer a Chinese made machine. My customer has a saw sold to him by the Italians that is made in Hungary, I believe. Took forever to get a wiring diagram out of them, because they didn’t make the machine, they only put their name on it.

 

[kwired]

Unfortunately the tech support does not know the answer either other than "the specs say not to use a high leg." The machine costs $85,000 so I have zero interest in experimenting to find out why


Thanks for the welcome. Seems as though Delta-Wye will be the best solution as I cannot seem to convince them to replace there service


Thank you sir, I will take a look

Is this VFD driven motor or across the line manual/magnetic contactor controlled? As many already mentioned the motor won't care about high leg or even corner grounded systems. VFD's however may not be designed for anything but 120 nominal to ground on all three lines. On board single phase controls?control transformers simply need be connected to the non derived phase if on a rotary converter as that voltage isn't always a stable 240.

If you opt to have a wye source for this, you don't need to replace the service, you just need a 240 delta to 208/120Y transformer sized to the kVA of the unit.

The reason rotary phase converters have a "high leg" is they are basically a delta wound motor, with your incoming 120/240 across one side, some capacitors added between the derived "phase" and one or both the other two lines the input is connected to to create enough phase shift to get it started spinning. Once up to speed the voltage between each corner is 240 volts ideally, reality is the derived phase will vary as loading varies. This could possibly be one reason they don't like rotary phase converters, particularly if they marginally sized that motor for expected load. That voltage imbalance doesn't change the overall load, but does result in high current in some windings and low current in others, the closer the motor is running at it's rated output the more those high currents will cause excessive heating on the portion of the windings that have high currents.

Back to the concept of the rotary phase converter - the voltage between each corner as I mentioned is 240 volts with 120 degree phase angles between each corner. Because the 120/240 supply circuit is grounded at it's mid point, if you draw that source as being in parallel with the side of the delta connected to it, you have 208 volts from that opposite corner to grounded mid point. So it essentially is the same thing as a high leg delta supply, but maybe not quite as stable of voltage on the high leg as a utility supplied delta would have. The larger the idler motor is though the more stable it can be - the flywheel inertia effect will help stabilize it if you don't add too much load too quickly.

Motors in general can take short time unbalances though without causing damages, and unless they are marginally sized to the driven load, they can take even more of such abuse.

Some these commercial wood working machines may never see rated load or at least not for very long at a time if they do in most shops is another thing to think about. But I also understand if it is a new machine, why would you want to do an install that may void any warranty?

If it is a new machine and ordered for where it is being installed, the question might be why did it not get ordered for what the existing supply has, or at least with conversion equipment to work with what is there? 240 volt high leg delta is not that rare of a system in North America. Some areas maybe is more rare than others but you can find these almost everywhere in the US to some extent.

 

[C4ctus99]

Seems to me that conversion to 480 V wye, @ 60Hz would have been the most practical choice.
The motor will run fine at that. What needs to be done with the control power is unknown.
That's a standard voltage transformer output here. What is unknown is if the site has an open delta service or not.
That could be an issue with voltage stability, depending on service size and other loads connected to the same service transformer bank.
Do you know if the service is supplied open delta ( two transformer pots instead of three) and what size is the service that they have existing ?

I agree, but waiting on the manufacturer for more information currently. Pole has 2 pots, if memory serves correctly, the high leg comes off its own pot and the two normal phases are off the second one. Service is 400A fused disconnect. High leg is 210V to ground

Is this VFD driven motor or across the line manual/magnetic contactor controlled? As many already mentioned the motor won't care about high leg or even corner grounded systems. VFD's however may not be designed for anything but 120 nominal to ground on all three lines. On board single phase controls?control transformers simply need be connected to the non derived phase if on a rotary converter as that voltage isn't always a stable 240.

Schematics show thermal magnetic contactor, however I believe there is a power supply between the contactor and motor that converts to 220V. I am beginning to think perhaps the power supply is what cannot handle the high leg.

Back to the concept of the rotary phase converter

Thanks for the more in depth explanation. This converter had 267V phase to ground, significantly higher than the incoming from utility...

If it is a new machine and ordered for where it is being installed, the question might be why did it not get ordered for what the existing supply has, or at least with conversion equipment to work with what is there? 240 volt high leg delta is not that rare of a system in North America. Some areas maybe is more rare than others but you can find these almost everywhere in the US to some extent.

They specified 240V for the machine and it was rewired from 480Y to 240D but apparently cannot have a high leg which makes no sense to me. Once again I am thinking the power supply may have something to do with it. I am waiting on the manufacturer to send the paperwork that specifies it. It may also be an artifact of the 480Y system that made its way into the 240D system since they seem to copy and paste a lot...

 

[MTW]

Pole has 2 pots, if memory serves correctly, the high leg comes off its own pot and the two normal phases lines are off the second one. Service is 400A fused disconnect. High leg is 210V to ground

Two pots is an open delta service. One phase from the larger of the two pots, (two lines L1 & L2), with a center taped coil with the neutral tapped in the middle of that pot coil.

The second pot provides L3, the high leg. The one that gives ~208V to the neutral, of the center tapped pot, and 240V to L1 and L3.

So open delta in reality, only has two phase coils. the third phase is virtual, there is no actual independent coil.
That is why the third line voltage can be varying and weak, and has a higher voltage to neutral and ground.
A lot depends on what the pot sizes are, in relation to how much actual load they each have on them.

The main pot with the center tap, carry's all of the 120V loads as well, that's why it is normally sized larger.



If I were in your shoes, I would likely use a standard 240V delta primary to 480/277V Wye /Star secondary transformer, which is standard equipment here, and have the vendor change whatever is necessary on the control end to match.

A 400V 50Hz motor will work fine on 480V 60Hz as the volts per hertz are the same.
400/50=8 480/60=8
Only real difference is the motor speed will be faster due to the frequency increase.

And since you need to get away from feeding open delta to the machine 480 is closer to 400 and can be well balanced and is standard available equipment. I often told the equipment vendors to cover the cost of the transformer, or I'm not connecting it. The vendor needs to learn to check the system type where they are selling equipment to, not put the burden the customer or contractor.

 

[tortuga]

but I would recommend the 240Y/139 as it gives you the chance to have a grounded secondary.

Yeah thats what I'd quote along with getting a quote from the POCO to either close the delta or if they are a POCO thats getting rid of delta's I might even ask them for a cost esitmate on providing a 220Y/127 service at the customers expense as neither of those involve any changes on the customer side.
I'd rather throw the $$ at the POCO for a transformer upgrade as the customer side transformer losses are forever on the monthly bill.
If they did do a customer owned 240Y/139 it might be worth considering a 240Y/139 panelboard as other equipment gets upgraded it will also probably want that.

and he said a senior engineer told him 245V max for the motor... so I may have another issue as our utilities like to run 245-249V

I doubt that, the EU's Low Voltage Directive (LVD) (2014/35/EU) state for their nominal 230V supply, the permitted voltage variation is +10% and -6%. This means any equipment made for the common market should accept a voltage range from 207V - 253V.
IEC 60038 allows +/- 10% voltage variation under normal conditions.
EN 50160 further defines normal as 95% of the time and does not have a limit for the other 5%.

 

[xformer]

Why not just Buck the Highleg?