how to wire a 6-lead, 480vac wye motor?

[emiller233]

While you are at it you obviously got hold of an IEC world standard motor. So let’s just guess FLA is about 85 A. That means locked rotor will be around 510 A for a couple seconds but that isn’t what tripped your main. These things hit over 20 times FLA or almost 2000 A inrush. If your breaker instantaneous is set low it will probably trip even if the fuse is current limiting.

Make friends at the motor shop. They will give you a booklet that has all the wiring charts for standard motors for free. There are 2 standard ways to correctly wire a 6 lead motor. There are about two dozen ways to wire it up total. Some work, some do nothing, some destroy it. Follow the book every time.

On six lead single voltage motors watch out and check the manufacturer diagrams. Most use the high voltage wiring diagram only. But at least one (Toshiba) does not.

Finally do not make bastard motors. Lead times are so long you can only rewind and with today’s energy efficient motors the laminations are getting so thin even with temperature controlled burnout the number of rewinds is limited. There are plenty of standard sizes to pick from.

i'll try and stick to the 2 standards
it is a 100HP motor thats derated to 75. i have no clue what kind of breaker it was. they didnt even want to say what happened moreless give details

 

[kwired]

While you are at it you obviously got hold of an IEC world standard motor. So let’s just guess FLA is about 85 A. That means locked rotor will be around 510 A for a couple seconds but that isn’t what tripped your main. These things hit over 20 times FLA or almost 2000 A inrush. If your breaker instantaneous is set low it will probably trip even if the fuse is current limiting.

Then factor in that it was configured for 240 volts and had 480 applied to it - inrush possibly was even higher than you mentioned.

I was surprised when OP mentioned they ran it for like 2 or 3 minutes at one time - you would think the smoke would have been obviously let out during that time, or that even would hold on the OCPD or motor overload for that long.

 

[paulengr]

Then factor in that it was configured for 240 volts and had 480 applied to it - inrush possibly was even higher than you mentioned.

I was surprised when OP mentioned they ran it for like 2 or 3 minutes at one time - you would think the smoke would have been obviously let out during that time, or that even would hold on the OCPD or motor overload for that long.

Inrush won’t change. It’s just the core energizing. It’s the old Steinmetz at work. Most people are surprised to learn that inrush and locked rotor currents are independent of load. And both are the best advertising there is for soft starters.

I’m not surprised it held out. Torque is roughly proportional to the square of voltage which was overdone by a factor of the square root of 2 and power also goes up the same way. So we doubled the flux. That’s the biggest issue. Assuming it wasn’t overloaded in the first place the load torque is fine. And it’s turning so we would expect it to self cool, no cooking in one spot in a stall. Overvoltage insulation breakdown is not likely a factor since it was such a short time so what ate it is joule heating from overfluxing the core. The motor became a mini burnout oven.

 

[winnie]

Although the nameplate says 240V in the delta configuration, it is reasonably a 277V motor when in delta. So it was only operating at 1.73x overvoltage, not 2x

 

[kwired]

Although the nameplate says 240V in the delta configuration, it is reasonably a 277V motor when in delta. So it was only operating at 1.73x overvoltage, not 2x

IEC standard voltages don't typically include 277 volts AFAIK. Would be typical for this motor to be used on 415/240 volt wye supply @ 50Hz.
Winding would be designed for 240 volts nominal. connect it to 240 volt three phase in a delta configuration and each winding sees 240 volts across it. Connect it to 415 volt three phase in a wye configuration and each winding still sees 240 volts across it.

Increase frequency to 60 Hz and to 480 volts and connect in wye configuration and then you have 277 across each winding, but at same time you are still close to same V/F ratio as 50 Hz and 415 volts - will be increased motor speed and output torque with little other issues, especially on a motor where they mark for use on 60 Hz systems where they took this into design considerations.

 

[emiller233]

so they sent the motor out and had it tested. they said it passed all tests, so that's a plus..! so they're getting ready to ship it back to us..

but our technician couldn't get the motor to start when the had it hooked up (PROPERLY) in the Y configuration. They even disconnected the shaft from the pump so that there's no load on it.
They said it hummed when they tried to start it. He said he checked voltage on all 3 legs and it was good, not sure WHERE he checked it at yet tho...? but he did send me a video of it finally
could it be anything other than one of the 3 legs not actually getting power, from a blown fuse, bad contactor, ect...?

see link below for a video of the motor humming when they tried to start it (Previously)
motor humming video

 

[kwired]

so they sent the motor out and had it tested. they said it passed all tests, so that's a plus..! so they're getting ready to ship it back to us..

but our technician couldn't get the motor to start when the had it hooked up (PROPERLY) in the Y configuration. They even disconnected the shaft from the pump so that there's no load on it.
They said it hummed when they tried to start it. He said he checked voltage on all 3 legs and it was good, not sure WHERE he checked it at yet tho...? but he did send me a video of it finally
could it be anything other than one of the 3 legs not actually getting power, from a blown fuse, bad contactor, ect...?

see link below for a video of the motor humming when they tried to start it (Previously)
motor humming video

lost phase seems very possible.

 

[paulengr]

so they sent the motor out and had it tested. they said it passed all tests, so that's a plus..! so they're getting ready to ship it back to us..

but our technician couldn't get the motor to start when the had it hooked up (PROPERLY) in the Y configuration. They even disconnected the shaft from the pump so that there's no load on it.
They said it hummed when they tried to start it. He said he checked voltage on all 3 legs and it was good, not sure WHERE he checked it at yet tho...? but he did send me a video of it finally
could it be anything other than one of the 3 legs not actually getting power, from a blown fuse, bad contactor, ect...?

see link below for a video of the motor humming when they tried to start it (Previously)
motor humming video

What tests? Quite often motor shops will just run a Baker test and treat it as gospel. Far from it! There are a number of faults it will not detect. Putting it on a test stand and running it at least no load and recording the three currents and comparing to typical data is also required.

On your end what condition is the compressor? Does the shaft turn freely or is it locked up? If you can’t turn it by hand there is something wrong and the motor is stalling. Current will read LRA, all three phases.

Also Its a lot of trouble to do this SAFELY and right now with no motor would be the ideal situation but there is nothing wrong with energizing a starter with the motor disconnected at the motor peckerhead to verify everything. Also need to check the primary side of a transformer if one is involved. With a delta-wye transformer if you have a missing primary phase the missing phase will be “regenerated” on the secondary side so measured without a load you will indeed see say close to 480 across the board. But it’s very high impedance and as soon as you apply a load, it suddenly reflects the correct (0) voltage. This will also locate loose connections, ground faults in the feeder cable, etc.

Another common problem with wye delta starters is the timer/current relay fails and it gets stuck in wye mode or one of the aux contacts has failed or the reactor in closed transition types (most are open transition). Also welded contactors can cause this. Open and inspect the contact tips. There are a lot more parts and things to go wrong. That’s why I recommend upgrading to electronic soft starts by the time you need to repair.

 

[synchro]

... our technician couldn't get the motor to start when the had it hooked up (PROPERLY) in the Y configuration. They even disconnected the shaft from the pump so that there's no load on it.
They said it hummed when they tried to start it. He said he checked voltage on all 3 legs and it was good, not sure WHERE he checked it at yet tho...? but he did send me a video of it finally
could it be anything other than one of the 3 legs not actually getting power, from a blown fuse, bad contactor, ect...?

Can you measure the current on each phase when trying to start the motor in order to verify that the phase currents are reasonably equal? For example, you could measure it with a current clamp in "inrush" mode to limit the time that the contactor is turned ON.

 

[emiller233]

Can you measure the current on each phase when trying to start the motor in order to verify that the phase currents are reasonably equal? For example, you could measure it with a current clamp in "inrush" mode to limit the time that the contactor is turned ON.

They should be getting the motor back into the shop today and getting it hooked back up. told them to try this. i don't know what meter hae has to know if it has 'inrush' on it or not. might just have a goold ole fluke clamp on out there..?

 

[kwired]

They should be getting the motor back into the shop today and getting it hooked back up. told them to try this. i don't know what meter hae has to know if it has 'inrush' on it or not. might just have a goold ole fluke clamp on out there..?

Most have a "peak" capture feature. How long the peak must occur before it is captured may be different from one to another and you may get different readings on same motor as a result. But a motor that isn't accelerating will have more of steady current level and a lost phase would still draw nothing if there is no other path for current to flow.

 

[emiller233]

What tests? Quite often motor shops will just run a Baker test and treat it as gospel. Far from it! There are a number of faults it will not detect. Putting it on a test stand and running it at least no load and recording the three currents and comparing to typical data is also required.

On your end what condition is the compressor? Does the shaft turn freely or is it locked up? If you can’t turn it by hand there is something wrong and the motor is stalling. Current will read LRA, all three phases.

Also Its a lot of trouble to do this SAFELY and right now with no motor would be the ideal situation but there is nothing wrong with energizing a starter with the motor disconnected at the motor peckerhead to verify everything. Also need to check the primary side of a transformer if one is involved. With a delta-wye transformer if you have a missing primary phase the missing phase will be “regenerated” on the secondary side so measured without a load you will indeed see say close to 480 across the board. But it’s very high impedance and as soon as you apply a load, it suddenly reflects the correct (0) voltage. This will also locate loose connections, ground faults in the feeder cable, etc.

Another common problem with wye delta starters is the timer/current relay fails and it gets stuck in wye mode or one of the aux contacts has failed or the reactor in closed transition types (most are open transition). Also welded contactors can cause this. Open and inspect the contact tips. There are a lot more parts and things to go wrong. That’s why I recommend upgrading to electronic soft starts by the time you need to repair.

it's a hydraulic pump, not a compressor but the guy knows his hydraulics for sure, so I'm assuming he's checked/verified everything is good on the front (i would hope...). he didn't measure the amps when he first attempted to run the motor unfortunately, he will theis time.

i've only been in that building once or twice, i have no idea what kind of setup they have? but this is great info! never considered a missing phase on the primary side of a transformer. and sounds like this could likely be the case bc he did say he checked voltage on all 3 legs but im assuming he did that when the the motor wasn't running? so when he tried to start they motor this voltage could drop like missing phase and giving the humming. he did however go grab another motor (not sure of the size) and run it on the same motor starter set that he has on his test bench and it ran fine, so fairly sure there's no issues there. 100% exact same setup down to the Meltric connector. and he said he's triple checked the continuity and checked for shorts from the Meltric connector to the end of the wires feeding the motor peckerhead

we're not using a Wye/delta starter, i was just confirming that we didn't need one really. other folks were saying we did. its just on a DOL motor starter. There's a soft starter on order for it, it's just not here yet unfortunately. and of course the deadline to test/ship this unit can't move so they're gonna go with what they got for now...


I just got the test report back from them a minute ago, see picture below. their email read:
We had a chance to check out motor.
We checked double checked and inspected the termination connection for 460 volts, WYE.
We also performed electrical testing to motor windings, Surge Comparison Test, And Megger Test.
All passed, We then connected and bench tested for 460 volts, Motor ran good with balanced
no load amps, Bench tested at rated voltage 460 volts, No Load Amps 60, 62, 62.