A 240v, 3 phase, 3 wire, balanced feeder to motor?

[Cartoon1]

I have an elevator motor that says exactly 'furnish a balanced, 3 phase, 3 wire electrical feeder system. I have a 240v, 3 phase feeder system in this building, a 3 phase high delta system tend to be unbalanced. Am I reading too much into this?? Does this need to be operated on voltages that can be balanced like 208. Even a 208v system can possibly be very unbalanced in some scenarios.

 

[Hv&Lv]

So you have a two pot bank or a 3 pot bank?
If you have a lot of load the delta really needs to be closed by adding a third transformer

 

[Cartoon1]

So you have a two pot bank or a 3 pot bank?
If you have a lot of load the delta really needs to be closed by adding a third transformer

Two pot

 

[TX+ MASTER#4544]

I have an elevator motor that says exactly 'furnish a balanced, 3 phase, 3 wire electrical feeder system. I have a 240v, 3 phase feeder system in this building, a 3 phase high delta system tend to be unbalanced. Am I reading too much into this?? Does this need to be operated on voltages that can be balanced like 208. Even a 208v system can possibly be very unbalanced in some scenarios.

2023 NEC
Section 430.24 Several Motors or a Motor(s) and Other Load(s) (1) (2) (3) (4)

You can use 208 volt motors but you need 208 volt system. They balance same way.

A three phase 240 volt3 wire delta system is what you describe. It has no neutral conductor.
How many motors do you have?

It means that you must balance the motors on each line or "group" (phase).
You do not want to put the 208 volt motors on a 240 volt feeder or vise versa,110.4 Voltages.
Need compatible voltage for them.

Since they are all three phase motors then it will be easy to balance them.
Draw 3 horizontal lines and connect each motor to each line (phase).

Assume no other loads, only motor loads.

Use T.430.250 for 3 phase motors amperages.

Take the largest motor amperage times 125 % and the remaining motors at 100 % amperage.

Add them all up to determine the feeder conductors. Size per T.310.16 75 degree terminals for ampacity.
After adding them all you must round down to determine the OCPD per T.240.6 (A)

For an example like this one I should sketch it out on paper for a better and more complete example.
For this reason I will not consider the required size of OCPD for the motors, which is unknown.

Thanks for reading.
TX+MASTER#4544

 

[LarryFine]

To me, the question is about present current load and additional capacity, not voltage, which is clearly a 240v high-leg open delta.

 

[Cartoon1]

To me, the question is about present current load and additional capacity, not voltage, which is clearly a 240v high-leg open delta.

I think the same, the load for this facility is low. The load for this facility at highest peak per utility is 35kw in the past 2 years, and their service is a 600a 240v/120v 3 phase. So the the facility has a low load in general. Adding this elevator adds maybe another 50A.

Of course the high leg usually tends to be sized smaller and I'm not sure how small or how much amperage pull is happening on the high leg.

 

[Cartoon1]

I think my question wasn't clear, I need to do a better job haha.
What I'm trying to say is basically: if the load on this facility is not an issue. I can still plug the elevator 240v 3phase even though the cut sheet says 'furnish a balanced, 3 phase, 3 wire electrical feeder system' and even though that the high leg service system on this property will not be a balanced system. Correct? Assuming the elevator motor is capable of doing 240v 3phase.

 

[kwired]

They probably mean symmetrical voltages to ground more so than how much loading is on the system. Basically means wye system instead of a delta system.

Surge protection incorporated in this may only be selected for say 150 -180 volts to ground before it starts clamping, which would be fine on a 208 wye system but on a high leg delta the high leg would burn out the one portion in short time as it operates above clamping voltage. A corner ground would burn out protection on both ungrounded legs as they are operating at full line to line voltage.

 

[electrofelon]

They probably mean symmetrical voltages to ground more so than how much loading is on the system. Basically means wye system instead of a delta system.

That's what I was thinking. It's poor/incorrect wording of course. Perhaps clarification with the manufacturer would be prudent.

 

[Hv&Lv]

I think my question wasn't clear, I need to do a better job haha.
What I'm trying to say is basically: if the load on this facility is not an issue. I can still plug the elevator 240v 3phase even though the cut sheet says 'furnish a balanced, 3 phase, 3 wire electrical feeder system' and even though that the high leg service system on this property will not be a balanced system. Correct? Assuming the elevator motor is capable of doing 240v 3phase.

With that loading you should be OK, unless the bank is something like a 35kVA bank.
Current imbalance shouldn’t be that big of a deal at the service.
Voltage imbalance is far more critical on any three phase motor. It causes excessive heating and can damage the motor with as little as 3% voltage imbalance
If your voltage readings under load are something like 242, 240, and 233 your going to have trouble..
How close are all your voltages now?

 

[TX+ MASTER#4544]

I think my question wasn't clear, I need to do a better job haha.
What I'm trying to say is basically: if the load on this facility is not an issue. I can still plug the elevator 240v 3phase even though the cut sheet says 'furnish a balanced, 3 phase, 3 wire electrical feeder system' and even though that the high leg service system on this property will not be a balanced system. Correct? Assuming the elevator motor is capable of doing 240v 3phase.

2023 NEC
430.24 (1)(2)(3)(4) Several Motors or a Motor and Other Load(s)

A 3 phase delta system with a high leg will not make any difference.
line to line is 240 volts including the wild leg which will be about 208 volts to ground but still you will have 240 volts between the phases.
240 volts x 1.732 = 208 volts to ground.
So, you still have 240 line to line and that's what you want.
You still have a balanced motor load.
I don't know anything about their current load or what's available for other motor loads.

An open delta may have to be replaced with a closed delta for additional capacity.

If some or all of these motors run at different times, use Section 430.23 (E) and the T.430.22(E) Duty Cycle Service
There is an elevator motor listed in the second row with minute rated motors and there percentages.
Article 100 Definitions with deferent duty types defined therein.

Thanks for reading.
Comments accepted.
TX+MASTER#4544

 

[Cartoon1]

With that loading you should be OK, unless the bank is something like a 35kVA bank.
Current imbalance shouldn’t be that big of a deal at the service.
Voltage imbalance is far more critical on any three phase motor. It causes excessive heating and can damage the motor with as little as 3% voltage imbalance
If your voltage readings under load are something like 242, 240, and 233 your going to have trouble..
How close are all your voltages now?

This is an existing facility and I don't think they have voltage issue. As far as what will happen once this motor gets connected then I don't know. What I do know is that the high leg is sized smaller than the others which is typical. Also what I know is that a peak is 35kw this facility has experienced, but I'm not sure how much that high leg is pulling in amperage since the only three phase motors on the facility are A/C.

 

[Cartoon1]

2023 NEC
430.24 (1)(2)(3)(4) Several Motors or a Motor and Other Load(s)

A 3 phase delta system with a high leg will not make any difference.
line to line is 240 volts including the wild leg which will be about 208 volts to ground but still you will have 240 volts between the phases.
240 volts x 1.732 = 208 volts to ground.
So, you still have 240 line to line and that's what you want.
You still have a balanced motor load.
I don't know anything about their current load or what's available for other motor loads.

An open delta may have to be replaced with a closed delta for additional capacity.

If some or all of these motors run at different times, use Section 430.23 (E) and the T.430.22(E) Duty Cycle Service
There is an elevator motor listed in the second row with minute rated motors and there percentages.
Article 100 Definitions with deferent duty types defined therein.

Thanks for reading.
Comments accepted.
TX+MASTER#4544

Good points, thank you. The voltage now seems okay. The high leg size worries me a little since the voltage could have issues once this extra load gets added to the system.