SLASH RATED BREAKERS

[fifty60]

If breakers that are rated 480Y/277 VAC are used at 50 Hz, does the slash rating have to derate to 400Y/230 VAC, or doe they keep their 480Y/277 VAC rating at 50Hz? Would it be OK to rate the equipment they are used in at 400Y/277 VAC?

 

[kingpb]

Depends on how well they play the guitar!!! :lol:

Typically, they will be rated at that voltage for 50 or 60Hz, but check with manufacturers product data sheets to confirm.

 

[templdl]

If breakers that are rated 480Y/277 VAC are used at 50 Hz, does the slash rating have to derate to 400Y/230 VAC, or doe they keep their 480Y/277 VAC rating at 50Hz? Would it be OK to rate the equipment they are used in at 400Y/277 VAC?

What do the specifications state on the breaker? What does the literature include?
Since you haven't made reference to the product that you intude O apply it is difficult to provide a diffinitive answer since there are so many products and manufactures out there.
For a product that I am thinking of this basically should be a none issue which may or may not be the case with the product you anticipate on using.
If splitting hairs is an issue technically the kaic will go up very sightly as kaic ratings are higher at lower voltages. In addition breakers ratings are commonly listed at 50/60z.
As long as your 480/277v breaker is applied at less than this voltage you are good to go. Incidentally that 277 refers to the line to ground voltage and as such can not be applied on systems with L-G voltages higher than that.

 

[fifty60]

Thanks for the input. It is helpful.

 

[Carultch]

If breakers that are rated 480Y/277 VAC are used at 50 Hz, does the slash rating have to derate to 400Y/230 VAC, or doe they keep their 480Y/277 VAC rating at 50Hz? Would it be OK to rate the equipment they are used in at 400Y/277 VAC?

The way that the slash rating works on a breaker, is that the lower voltage specifies volts-to-ground, and the higher voltage specifies maximum volts across any pair of connections to it. One place you might see this, is if you attempt to connect a two pole breaker on a high leg delta system. Even though it is rated 240V pole to pole, there is an issue with connecting it from the high leg to the adjacent pole for a 240V load, if it is slash rated. Volts to ground would exceed 120V. You can use it across A and C phases, but not the high leg. Straight rated breakers are required for the high leg.

Most breakers are dual rated at 50/60 Hz, and there really isn't a physical reason why using a 60Hz breaker at 50Hz would change the voltage rating, if at all. Look for this dual frequency rating, or check with the manufacturer if documentation only indicates 60 Hz.