2KVA Transformer Protection

[faresos]

I have a situation where I need to provide 2KVA, 480V pri, single phase, 120V sec transformer to power an external power outlet. My question, do these kind of transformer comes with internal fuses for primary and secondary protection or that something we need to provide? The application will be to provide 480V, 3-Phase circuit to power a gate motor and will need to tap from this line (L1 & L2) to get 480V and step it down to 120V to power this outlet. Any thoughts on the best way doing it?

Thanks

 

[ptonsparky]

You need to provide primary and secondary protection.
Table 450.3(B) is a good starting point. You will also need to consider the protection for the conductors.

eta: 240.21

 

[petersonra]

I have a situation where I need to provide 2KVA, 480V pri, single phase, 120V sec transformer to power an external power outlet. My question, do these kind of transformer comes with internal fuses for primary and secondary protection or that something we need to provide? The application will be to provide 480V, 3-Phase circuit to power a gate motor and will need to tap from this line (L1 & L2) to get 480V and step it down to 120V to power this outlet. Any thoughts on the best way doing it?

Thanks

you can buy the transformer with the fuse blocks or without. Either way, generally you have to supply the fuses.





You can get fuse blocks just on the primary side, just on the secondary side, or on both sides. It just depends on what part number you order.

 

[hillbilly1]

you can buy the transformer with the fuse blocks or without. Either way, generally you have to supply the fuses.

View attachment 2557931

View attachment 2557932

You can get fuse blocks just on the primary side, just on the secondary side, or on both sides. It just depends on what part number you order.

Usually those will be substantially less than the 2 kva the op is looking for, but since the gate is 480 three phase, I’m wondering what will need 2 kva? One these you have shown may be more than enough for the load.

 

[kwired]

Usually those will be substantially less than the 2 kva the op is looking for, but since the gate is 480 three phase, I’m wondering what will need 2 kva? One these you have shown may be more than enough for the load.

My guess they want general use 15/20 amp 120 volt receptacle(s) maybe even lighting circuit in the vicinity. Might get by with 1 or 1.5 kVA transformer. Ones shown probably only 250 VA or less and probably more of a control transformer than a power transformer.

BTW if set up as 480 x 120 you can protect both primary and secondary with primary only OCPD. If set up as 480 x 120/240 you need both primary and secondary protection, but primary can be possibly be a higher setting in this case also.

 

[petersonra]

Usually those will be substantially less than the 2 kva the op is looking for, but since the gate is 480 three phase, I’m wondering what will need 2 kva? One these you have shown may be more than enough for the load.

It's just a picture, not an application suggestion. There are larger single phase xfmrs with. Built in fuse blocks too.

The op could also just buy a transformer in a box with the xfmr, disconnect, fuses and outlet already done. Much cheaper usually than making it yourself.

Again, just a picture, not an application suggestion. These kind of things can be gotten in a type 3r enclosure with GFCI and in use cover too. Pretty much you can order what you want. Maybe not from this supplier but plenty of people make these.

 

[hillbilly1]

I would think maybe cameras, or other low draw equipment. Even lights now are LED, so not much draw.

 

[faresos]

Thank you all for the replies. The application is to power an outlet within an access control cabinet located adjacent to the gate operator controller. I believe I still need to provide a disconnect a head of the transformer and I might just make it fused disconnect and then provide a fuse block for the secondary then run the wires to the cabinet to power the outlet. That way I still have a way to disconnect the power to the transformer and the outlet if needed.

 

[hillbilly1]

Thank you all for the replies. The application is to power an outlet within an access control cabinet located adjacent to the gate operator controller. I believe I still need to provide a disconnect a head of the transformer and I might just make it fused disconnect and then provide a fuse block for the secondary then run the wires to the cabinet to power the outlet. That way I still have a way to disconnect the power to the transformer and the outlet if needed.

You may not need 2 kva then. The transformer does not have to provide a full 15 amps to the load, if it is fused correctly. But hey! If they want to spend the money, that’s more money in your pocket! LOL!

 

[petersonra]

You may not need 2 kva then. The transformer does not have to provide a full 15 amps to the load, if it is fused correctly. But hey! If they want to spend the money, that’s more money in your pocket! LOL!

My guess is the labor will exceed the cost of the parts anyway

 

[faresos]

yeah the whole thing didn't make sense to me. Originally, I provided 120V circuit (120ft away only, VD is not an issue) to this outlet but the customer said they want a step down transformer (480V-120V). I don't believe the load will exceed 600VA but the client requested 2KVA xfmr.