60 to ground

[jjwitty]

I have been working on a stretch wrapper, and the wrapper motor won’t kick on. I have 2 issues, one is the resistance of the strain beams, and two is my control power.

When I turn machine on without control power, I have 120 to ground. When I have control power, I get 60 to ground on hot and neutral. I cannot for life of me find any buried neutrals or loose wires. I’m not sure is this alone is even enough to stop the machine from working. I thought it would work but be unsafe, that’s why I am fixing it. I realize something in my control circuit is not wired correctly. I’ve tried unplugging each device while measuring voltage back to ground and nothing changes. Any thoughts?

 

[LarryFine]

It sounds like your control circuit is floating, i.e., neither supply conductor grounded.

 

[qcroanoke]

I have been working on a stretch wrapper, and the wrapper motor won’t kick on. I have 2 issues, one is the resistance of the strain beams, and two is my control power.

When I turn machine on without control power, I have 120 to ground. When I have control power, I get 60 to ground on hot and neutral. I cannot for life of me find any buried neutrals or loose wires. I’m not sure is this alone is even enough to stop the machine from working. I thought it would work but be unsafe, that’s why I am fixing it. I realize something in my control circuit is not wired correctly. I’ve tried unplugging each device while measuring voltage back to ground and nothing changes. Any thoughts?

Has this machine been working?

 

[jjwitty]

It sounds like your control circuit is floating, i.e., neither supply conductor grounded.

Has this machine been working?

The stretch wrap motor stopped working one day. The motor kicks on when a transducer senses resistance on a roller. I took apart the roller and noticed the transducers were bent, so I replaced. The motor still didn’t work so I explored other possible reasons. I am gettin 120 between L&N, so to me the motor should kick on. Btw the 120 is converted to 90vdc to power the motor.View attachment 2573894

 

[jjwitty]

If you look in the pictures you see that control circuit. My 120 is normal until that MCR1&2 energizes. Like I said, I’m not sure if this is why the motor won’t kick on or not. I also attached the circuit with the DC 90 v motor and the control board for the motor.

 

[LarryFine]

If you look in the pictures you see that control circuit.

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[jjwitty]

 

[jjwitty]

My 120 is normal until MCR1&2 energizes.

 

[ptonsparky]

We can’t see the entire circuit and we also need to see the control transformer.
What is the voltage to the machine? Where does it come from? A customer owned step down transformer? What is the building served with?

 

[jjwitty]

We can’t see the entire circuit and we also need to see the control transformer.
What is the voltage to the machine? Where does it come from? A customer owned step down transformer? What is the building served with?

I added a 480/120 CT. What’s strange is I don’t remember seeing this CT outside the drawing. I can account for one 120:24 power supply, and one 120/24 CT. The machine is 480 3 phase. The building is a delta transformer.

 

[TwoBlocked]

I added a 480/120 CT. What’s strange is I don’t remember seeing this CT outside the drawing. I can account for one 120:24 power supply, and one 120/24 CT. The machine is 480 3 phase. The building is a delta transformer.

Sorry, the image is incomplete. But you say you ADDED control transformers??? Why? Btw, "CT" usually means "Current Transformer." Using"xfmr" would be more clear.

 

[ptonsparky]

Yes

Sorry, the image is incomplete. But you say you ADDED control transformers??? Why? Btw, "CT" usually means "Current Transformer." Using"xfmr" would be more clear.

Why and where?

 

[rlundsrud]

You need to make sure the secondary of your 480/120 transformer is grounded as shown. If it is left floating, you can see voltages fluctuate in the way you're describing.

 

[jjwitty]

You need to make sure the secondary of your 480/120 transformer is grounded as shown. If it is left floating, you can see voltages fluctuate in the way you're describing.

We have two machines with that are identical. I measured voltage on the other one and it’s the same and that machine works. Ended up recalibrating the dc motor control board and machine works.

 

[ptonsparky]

We have two machines with that are identical. I measured voltage on the other one and it’s the same and that machine works. Ended up recalibrating the dc motor control board and machine works.

You got it to work and that's what counts, but I thought the question was why the 60 volts.

 

[jjwitty]

You got it to work and that's what counts, but I thought the question was why the 60 volts.

You’re correct, the question still there. I looked at the transformer and it’s bonded.

 

[jim dungar]

Btw, "CT" usually means "Current Transformer." Using"xfmr" would be more clear.

I like to use CPT for control power transformer. As you said, there are quite a few devices that start with C and T, especially in control and measuring circuits.

 

[jim dungar]

My 120 is normal until MCR1&2 energizes.

At which points in the circuit are you making measurements?