Control Transformer Question

[Riponguy]

Hello everyone... I am installing a 12vdc tachometer on a industrial mixer. There is 480v 3ph motor starter with disconnect box near the machine with a 480v to 120v control power transformer in it. I was going to wire a typical plug in style 12vdc power supply to this 120v supply, but it didn't work. I realized the output of the xfmer was floating, so I grounded the X2 output. I then had 120v across the xfmer and to ground. I hooked my power supply back up, and for some reason I let the smoke out of it. What am I missing or doing wrong? Thanks!
Source URL: Control Transformer wiring - https://www.electriciansforums.net/threads/control-transformer-wiring.184228/

 

[westward10]

Hello you have two threads running, identical apart from one being 12v the other 24v. Which one is relevant.

 

[Megawatt]

Hello everyone... I am installing a 12vdc tachometer on a industrial mixer. There is 480v 3ph motor starter with disconnect box near the machine with a 480v to 120v control power transformer in it. I was going to wire a typical plug in style 12vdc power supply to this 120v supply, but it didn't work. I realized the output of the xfmer was floating, so I grounded the X2 output. I then had 120v across the xfmer and to ground. I hooked my power supply back up, and for some reason I let the smoke out of it. What am I missing or doing wrong? Thanks!
Source URL: Control Transformer wiring - https://www.electriciansforums.net/threads/control-transformer-wiring.184228/

Ripinguy on a 3 phase transformer 480vac you should have bonded XO not. If it’s a control transformer and read the manufactures wiring diagram. I can’t understand why you are plugging in a 12vdc in a 120 supply. That control transformer is for the motor starter and it’s controls only. It don’t have but a 2 amp fuse in it and it’s bonded a the factory. I would like a little more info

 

[Riponguy]

Ripinguy on a 3 phase transformer 480vac you should have bonded XO not. If it’s a control transformer and read the manufactures wiring diagram. I can’t understand why you are plugging in a 12vdc in a 120 supply. That control transformer is for the motor starter and it’s controls only. It don’t have but a 2 amp fuse in it and it’s bonded a the factory. I would like a little more info

12vdc is the correct post... I meant to go back and edit, but got called away.
[automerge]1583846862[/automerge]

Ripinguy on a 3 phase transformer 480vac you should have bonded XO not. If it’s a control transformer and read the manufactures wiring diagram. I can’t understand why you are plugging in a 12vdc in a 120 supply. That control transformer is for the motor starter and it’s controls only. It don’t have but a 2 amp fuse in it and it’s bonded a the factory. I would like a little more info

Yes, it is a control transformer that is stepping down the 480vac in the panel to 120vac to operate the start/stop/safety circuit. It is the only nearby 120v power source. I was going to direct wire a 12vcd power supply to it to power my tachometer. Is this possible?

 

[Megawatt]

12vdc is the correct post... I meant to go back and edit, but got called away.
[automerge]1583846862[/automerge]

Yes, it is a control transformer that is stepping down the 480vac in the panel to 120vac to operate the start/stop/safety circuit. It is the only nearby 120v power source. I was going to direct wire a 12vcd power supply to it to power my tachometer. Is this possible?

That makes sense with a power supply and I’m going to say yes you should be able to use that transformer for your power supply. Good luck

 

[norcal]

One thing to consider, is the control X-former large enough to handle the additional load, or was it sized to be just adequate for the existing load?

 

[Darkwood]

I would be very cautious about strapping down one leg of the TX output unless you understand the control wiring fully, doing so may cause issues elsewhere or even risk of shock in some cases.

What is the nature of the DC power supply?