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Discussion Starter · #1 · (Edited)
I have a fire pump it's a 12 lead wye start delta run. It's a 480 motor I wired it up as per normal high voltage 12 lead wye start delta run. I have hooked many up before. Now this appears to be a single voltage motor. The tech told me that it must be wired as if it was low voltage even though it's being hit with 480. Does that sound right? I'd think if it was single voltage 480 it would be wired as high voltage. Usual 4-7, 6-9, 5-8 with parallel feeds hitting 1, 2, 3 and 12, 10, 11
 

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Donuts > Fried Eggs
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"Wired as if it was low voltage" is misleading because all you're doing is changing the winding configuration, not the voltage rating.

If you reduced the voltage then it would draw the same current in a Δ as it does when high voltage is supplied to to a Y, that's why he's calling it the "low voltage" configuration. But because you're not changing the supply voltage, it means that during Y start it just draws less current.
 

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Did you test run it after making your connections? What was the performance and amperage readings?
 

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Discussion Starter · #4 · (Edited)
We never got a chance to kick it on...damn techs took a 2hr+ lunch. I did some searching and a single voltage 12 lead wye start delta run is wired the exact way as the low voltage wiring for dual voltage 12 lead wye start delta run.:001_huh:


All the 12 leads I have come across have been dual voltage, this is the first time wiring a single voltage 12 lead. I just instinctively wired it up as high voltage since we were hitting it with 480v.

I'll admit motor controls aren't my strong point....just seems strange hitting it with 480v but wiring it up as if it was low voltage.
 

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Electrical Simpleton
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I believe you will end up with 6 conductors feeding this motor.

One set of 3 for start and one set of 3 for run. The controller takes care of switching between the sets.

Pete
 

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Discussion Starter · #6 ·
I already ran my wire and set up the controller the issue was wiring on motor side. There are 3 contractors one gives you your wye then it drops out and the third one closes sending 480v down your second feed as well giving you delta run
 

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Electrical Simpleton
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I already ran my wire and set up the controller the issue was wiring on motor side. There are 3 contractors one gives you your wye then it drops out and the third one closes sending 480v down your second feed as well giving you delta run
I will admit I have limited experience with this set-up but I know for a fact that there are two sets of three wires feeding the motor.

Pete
 

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Bilge Rat
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A lot of 12 lead single voltage motors I work with are indeed connected 'low voltage'.

This means that L1 goes with T1, T6, T7 and T12; L2 goes with T2, T4, T8 and T10; L3 goes with T3, T5, T9 and T11.

This is done so the motor can be started across the lines, Y-∆, or part-winding. If it were designed to be connected 'high voltage', it could not be started Part-winding.

The main advantage to part-winding start is that only two contactors are needed. Y-∆ uses 3, and 2 of them need to be electrically and mechanically interlocked.

The main disadvantage is that it cannot be left in start for more than a couple of seconds, Y-∆ can be in start (Y) for a fairly long time.
 

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Bilge Rat
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I already ran my wire and set up the controller the issue was wiring on motor side. There are 3 contractors one gives you your wye then it drops out and the third one closes sending 480v down your second feed as well giving you delta run
If the starter is indeed a Y-∆ (sounds like it is), then 6 wires are needed from the starter to the motor. Each wire needs to be rated for 58% of the full-load current.

The wires that go from the single contactor go phase A to T1,T7; B to T2,T8 and C to T3,T9.

The wires that go from the interlocked contactors go phase A to T6,T12; B to T4,T10 and C to T5,T11.
 

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Discussion Starter · #10 ·
If the starter is indeed a Y-∆ (sounds like it is), then 6 wires are needed from the starter to the motor. Each wire needs to be rated for 58% of the full-load current.

The wires that go from the single contactor go phase A to T1,T7; B to T2,T8 and C to T3,T9.

The wires that go from the interlocked contactors go phase A to T6,T12; B to T4,T10 and C to T5,T11.
Correct that is how it is now wired, the ones I have worked with before were all dual voltage and the wiring you listed would be the low voltage wiring. I just don't understand why the single voltage 12 lead wye start delta run would be wired as if it was low voltage in a dual voltage 12 lead Y start D run.
 

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Bilge Rat
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I just don't understand why the single voltage 12 lead wye start delta run would be wired as if it was low voltage in a dual voltage 12 lead Y start D run.
A 12 lead motor can be part-winding started only on the low voltage connection, not the high voltage.

If the motor drives a load that's easy to accelerate, a part-winding starter for a big motor is a LOT less expensive than a Y-∆ one.
 

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Discussion Starter · #12 ·
I understand the need for low voltage with partial winding start but in this case it uses Y start D run. Sorry if I'm just not getting it. I'm just trying to understand why we would use Y start D run then hook it up as if it were low voltage. What would be the advantage?
 

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Bilge Rat
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I understand the need for low voltage with partial winding start but in this case it uses Y start D run. Sorry if I'm just not getting it. I'm just trying to understand why we would use Y start D run then hook it up as if it were low voltage. What would be the advantage?
Since it's a single voltage motor, the manufacturer made it so it could be started either Y-∆ or part winding. The only way to do this is to have it connected for low voltage of a dual voltage motor.
 

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Discussion Starter · #14 ·
Ok I wasn't thinking about the partial winding start, think I get it so since the windings are all going to be in parallel (as it is wired for low voltage) I'm assuming the windings have been installed to accommodate 480. So if I was to wire this motor in series (high voltage) it would be at reduced RPM with very little torque?
 

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Is it by chance a Weg motor?

A 12 lead motor IS in fact a dual voltage motor, always. The reason for my asking if it is Weg is because Weg, being a Brazilian company, sells a lot of motors into the mining industry in Brazil and to reduce the conductor size on trailing motors, they use 690V 50Hz as a motor voltage above 250HP. So sometimes in an inventory pinch, Weg will sell one of those to a customer in the US looking for a 480V 60Hz motor, because a 690V 50Hz Star connected motor, will run at 400V 50Hz if connected in Delta, which is the same V/Hz ratio as 480V 60Hz so the motor runs fine and provides full torque, just at a faster RPM.

So that might be why your tech told you to wire it up as Low voltage; as far as the motor design is concerned, that's what you are giving it.
 

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Bilge Rat
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Ok I wasn't thinking about the partial winding start, think I get it so since the windings are all going to be in parallel (as it is wired for low voltage) I'm assuming the windings have been installed to accommodate 480. So if I was to wire this motor in series (high voltage) it would be at reduced RPM with very little torque?
If this motor were to be connected in series (high voltage), it'd want to see 920 volts in order to produce its rated HP.

The speed would be the same, but it'd produce about 1/4 of its rated HP.
 
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