Transformer...almost there

[Pierre C Belarge]

Thanks Jim, I'm not using secondary OCP since I've protected the primary (208 volt at 125%)

I think I'm getting it although I think there could be a shock hazard if certain conditions were met. As in my post above. I hope I'm wrong.

You most likely found this info in Article 450, That is for protecting the windings, not the conductors.


You are required to have protection on the secondary side, see 240.21(C)and 408.36(D).
This is going to affect the type of circuit breaker you will need. If you are installing this tomorrow, I would call your supply house(s) to see if they have the proper size and type available.

 

[jim dungar]

You most likely found this info in Article 450, That is for protecting the windings, not the conductors.


You are required to have protection on the secondary side, see 240.21(C)and 408.36(D).
This is going to affect the type of circuit breaker you will need. If you are installing this tomorrow, I would call your supply house(s) to see if they have the proper size and type available.

This is a single output voltage transformer (delta-delta) so it is possible for the primary protective device to also protect the secondary conductors.

 

[Pierre C Belarge]

This is a single output voltage transformer (delta-delta) so it is possible for the primary protective device to also protect the secondary conductors.

I was wondering how you knew that...so I went back in the thread and saw the figure... go figure.

 

[hurk27]

I think I got it. I will pull a grey to the equipment (instead of an orange). I'm grouding the H2 leg to building steel and a ground rod. What would happen if say someone would be touching the frame of the machine and say a part of the building that has a slightly higher impedance to ground (say building steel with a loose bolt). Could there be a potential difference between the machine's frame and the building steel? Would the be a shock hazard there?

Thanks for all responses

If you bond the "B" phase at the transformer, then run a separate EGC/ conduit to the equipment. just don't make the grounding part of the current carrying pathway, the gray conductor can't be bonded after it leaves the transformer, it must be kept isolated, this will prevent this shock hazard you are worried about

 

[Bosco]

Thanks Wayne. That's exactly what I did:smile:. Thanks to all that replied. The machine works great. I was able to get 420 out of the xformer. They are cutting away as we speak.

Now can someone help me get my check from them?:grin:


Just kidding

Thanks again for all the help

Tony (aka Bosco)

 

[Besoeker]

This is a single output voltage transformer (delta-delta) so it is possible for the primary protective device to also protect the secondary conductors.

Maybe...
A couple of thoughts from how we do it.
The primary protection has to take account of inrush current that won't be seen by the secondary winding.
Output conductors would usually be sized to suit the load rather than the transformer rating and protected accordingly.
In short, it is our practise to protect on both sides and all conductors.
It may be beyond mandatory requirements but it is in line with customer specifications and expectations.
If you contract to do so, you do so.