Transformer question

[ggunn]

I have been asked to generate a 240/120V split phase circuit from 480/277V. I'm thinking that I will connect the primary of a 480V to 240V split phase transformer to two phases of the 480/277V without the neutral; is that correct? Does anyone make a transformer like that with no neutral on the primary side or can I just leave the primary neutral floating?

 

[infinity]

This is similar to what you're looking for only difference is that the output is straight 240 volts. You would connect the neutral where the system bonding jumper is installed to get 1Ø, 120-240.

 

[ggunn]

This is similar to what you're looking for only difference is that the output is straight 240 volts. You would connect the neutral where the system bonding jumper is installed to get 1Ø, 120-240.View attachment 2581688

Now that you mention it, I'm not sure the customer needs the neutral on the secondary side; I will check. FMI, how many kVA is that tranny? Y and O are primary, R and B are secondary? The SBJ is connected to the mid point on the secondary between the two coils, correct?

 

[electrofelon]

Now that you mention it, I'm not sure the customer needs the neutral on the secondary side;

Prolly best to still ground the center tap even if you dont need it for a circuit conductor (IIRC required by code anyway).

 

[ggunn]

Prolly best to still ground the center tap even if you dont need it for a circuit conductor (IIRC required by code anyway).

Agreed

 

[hillbilly1]

I have been asked to generate a 240/120V split phase circuit from 480/277V. I'm thinking that I will connect the primary of a 480V to 240V split phase transformer to two phases of the 480/277V without the neutral; is that correct? Does anyone make a transformer like that with no neutral on the primary side or can I just leave the primary neutral floating?

Primary will not need a neutral, all you need is two phases on the primary. No neutral pulled with the feeder, just the egc, which would just go to the transformer frame.

 

[infinity]

Now that you mention it, I'm not sure the customer needs the neutral on the secondary side; I will check. FMI, how many kVA is that tranny? Y and O are primary, R and B are secondary? The SBJ is connected to the mid point on the secondary between the two coils, correct?

Yes, 480 volts in, 240 volts out. 50 kva. This should be the nameplate.

 

[jim dungar]

Doesn't the NEC requires you to bond systems to <150 L-G when possible? If it is a possible connection, per the nameplate, is that sufficient?