transformer fusing

[zooby]

---277V light poles (led) . Management wants the 120V Christmas wrap lights lit up. Boss got 75va 277-to-120 autotransformers so a gfi can be installed for these. Does this need to be fused? If so, at what point?
This is a last minute thing. A 120V circuit will be pulled in later on.....I'm told. Thanks much.

 

[augie47]

Seemingly it would be a small power transformer and not actually an autotransformer. As such it should be protected per 450.3b (167% of secondary current)

 

[zooby]

Seemingly it would be a small power transformer and not actually an autotransformer. As such it should be protected per 450.3b (167% of secondary current)

i was just parroting what the info on the transformer says. Thanks !!

 

[augie47]

Disregard my post. I did not think an autotransformer would provide that much reduction but I did find one made by Hatch.

 

[jim dungar]

Disregard my post. I did not think an autotransformer would provide that much reduction but I did find one made by Hatch.

Not all autotransformers are the Buck-Boost variety, although that may be the most common application.

 

[augie47]

Art 450 advises protect it at 167% of the input current.

 

[zooby]

Disregard my post. I did not think an autotransformer would provide that much reduction but I did find one made by Hatch.

That's the manufacture of the ones i was given. Thanks for you time. It is appreciated. Now to find a hand hole stretcher to make this happen

 

[Strathead]

Not all autotransformers are the Buck-Boost variety, although that may be the most common application.

Technically aren't they all? Now a transformer may have several coils and be able to be connected as a buck, a boost or an isolation transformer, but when hooked up as an autotransformer, that, by its nature is a buck or boost, or a filter.

 

[jim dungar]

Technically aren't they all? Now a transformer may have several coils and be able to be connected as a buck, a boost or an isolation transformer, but when hooked up as an autotransformer, that, by its nature is a buck or boost, or a filter.

Yes, most 2winding transformer can be configured in different ways. The industry views, particularly manufacturers catalogs and electricians handbooks, 'buck-boost' as making relatively small , <15%, voltage changes.