Sharing neutrals in lighting circuits

[don_resqcapt19]

Roger,
As Jon has shown the power from the supply system does not change based on the internal motor windings. The power requirement for a 3 phase 10 hp motor is the same for either type of internal connection. It is also the same for either voltage. Look at the current ratings for a dual voltage motor. The current at 240 volts is twice that at 480 volts making the power the same for either voltage. Also look at Table 430.250. If there was a difference in power based on the internal wye or delta connection, then we would need a different table for each type of connection.
Don

 

[ramsy]

Right, load VA, Watts, Horespower, and supply power never changes, but what prevents operators from preferring motor terminals be Wye connected, or switching them, so "the _external_ terminal voltages and currents would change", not the power, as Jon described.

The cost of higher current was not refering to motor power consumption, but installation expense due to motor feeder/conductor size (copper costs) & perhaps relative IR^2 losses.

Choosing higher voltage and lower current has a material cost advantage, even though the power is identical.

 

[ramsy]

I am simply suggesting one common factor may be Wye connected motor loads, since Wye's don't dampen noise, and are the less common configuration for motors (rare).

That was a mistake.

Wye run motors could be a common factor for EDM fluting, but not because they are rare. We all agreed Wye run motors are the majority after all, but thats not what I miss wrote above.

 

[don_resqcapt19]

Roger,

Choosing higher voltage and lower current has a material cost advantage, even though the power is identical.

True but that has nothing to do with delta or wye motor connections. That is a system and equipment voltage issue. Also one of your posts talked about changing a motor from delta to wye. With the standard 9 lead three phase motors you can' do that. You must have a 12 lead motor for that.
Don

 

[ramsy]

..that has nothing to do with delta or wye motor connections.

So, while 3?, 12-lead motors may permit arranging coils between delta & wye current vectors, switching voltage in a 9-lead motor only changes the same coils between series or parallel.

We are always stuck with these motor's fixed choice of delta or wye design. Just like we are stuck with single phase motor leads that only arrange coils between series and parallel to change the voltage.

So, if 3?, 9-lead motors are most commonly run as wye's, operators did not choose to wire them that way, they must be spec'd & designed that way.

So, finally if I wanted to test EDM fluting effects just between the Delta & Wye motor design, exluding other factors, a 3?, 12-lead motor would be required?

 

[don_resqcapt19]

Roger,

So, finally if I wanted to test EDM fluting effects just between the Delta & Wye motor design, exluding other factors, a 3?, 12-lead motor would be required?

The 12 lead motors are intended for wye start delta run. If you want to test the same motor in both wye and delta configurations, you will need two different power supplies. This motor is designed to run as a delta motor and will require 240 or 480 volts. If you want to run it as a wye at full power, you will need a 415 or 830 volt power supplies.
Don

 

[winnie]

If you want to run this as an experiment, I would suggest getting two unwound motor frames from a manufacturer, and having a motor repair/rewinding shop design matched windings for the job. We've done this to test the performance of different phasing layouts; we were never looking at bearing life for these applications.

By selecting correct wire size and number of turns, you can build up motors that have the same copper slot fill and the same external terminal voltage and current, but which are internally wye or delta connected. By using two matched unwound frames, you have matching magnetic properties and don't have to worry about the damage caused by burning out the old windings. By having a winding shop do the two motors at the same time, you can specify having the same copper fill and having construction that is as similar as possible given the essential difference of wye versus delta connection.

-Jon

 

[GeorgeB]

Roger,

So, finally if I wanted to test EDM fluting effects just between the Delta & Wye motor design, exluding other factors, a 3?, 12-lead motor would be required?

The 12 lead motors are intended for wye start delta run. If you want to test the same motor in both wye and delta configurations, you will need two different power supplies. This motor is designed to run as a delta motor and will require 240 or 480 volts. If you want to run it as a wye at full power, you will need a 415 or 830 volt power supplies.
Don

Don's point is accurate (as usual), but I'd like to throw in something he didn't WRITE; and which I ASSUME we all know. When he says "The 12 lead motors are intended for wye start delta run.", he means "The 12 lead motors are intended for wye start delta run CAPABILITY ON EITHER OF THE 1:2 VOLTAGES." We need those 1:1.73 related voltages to fully load it in the wye when it is designed to run in delta. All standard nominal 230/460 motors with 12 leads of which I'm aware are designed to RUN in delta. Those with 9 leads are designed to run in wye.

3 lead, single voltage (as pointed out in this thread, we don't know or care if wye/delta in most cases).

6 lead, single voltage, wye-delta start CAPABILITY at specified voltage or dual, sqrt(3) related voltages (not the 1:2 230/460 stuff, the 1:1.73 230/400 stuff used on 50Hz systems.) Wye-delta on lower voltage only. This is a common configuration in Europe on motors in the 5 to 100 kW range. I've only seen it in the USA on large motors, 150HP and above.

One of the most interesting hydraulic troubleshooting calls I've been on was an OEM installed system running on 460 with a motor designed for delta but wired wye with single contactor; started (unloaded) fine, ran (lightly loaded for 80% of machine cycle) fine at LOW current, but tripped heaters and stalled 2 or 3 times a day with a calculated max load of under 75% of motor capability. OOPS, running at 58% of rated voltage ... amazing it did as well as it did. Effectively starting wye and never transitioning to delta. OEM had blamed the hydraulics for 18 months and 5 service calls.

9 lead, dual (1:2) voltage. Wye only.

12 lead, dual (1:2) voltage, wye-delta CAPABILITY on either voltage. To run wye, needs non-standard power supply.

 

[iwire]

So, finally if I wanted to test EDM fluting effects just between the Delta & Wye motor design, exluding other factors, a 3?, 12-lead motor would be required?

Roger I have not seen anything that suggests the problem or fix comes from motors wired delta or Wye.

The issue seems to be the large VFDs.

Now that we have ceramic coated bearings in the motors the problem will not show up in the motors again. It will likely show up in the fan bearings that the motor spins.

The motor shaft is coupled directly to the fan shaft through a non insulting coupling.

Since replacing the motor bearings the new path to ground for this induced voltage is through the fan bearings.

According to the GE motor techs this issue is becoming very common with the large amount of VFDs in service now and is not easy to fix.

They do a lot of sewage treatment plants and this problem is showing up in the large VFD controlled pumps.

 

[ramsy]

Roger I have not seen anything that suggests the problem or fix comes from motors wired delta or Wye. The issue seems to be the large VFDs. ..(and) is becoming very common with the large amount of VFDs in service now and is not easy to fix.

Fair enough. I didn't find any published fixes for fluting mentioning Delta or Wye issues either. However, my motor reading resources lacked in comparison to the contributions people made here.

If my read of the motor experience and engineering assists just given here is correct, the idea of noise-dampening Delta's is unlikely if anyone reports seeing a 12-wire motor (Delta run) with similar fluting problems. iwire, may have been dealing with 12-wire motors, or maybe not?