SSCR limitation with Circuit Breakers

[Butters]

I have a customer that wants to use Circuit Breakers only. Their panel is a single VFD and a control transformer for the 120vac controls. We need to achieve a SSCR of 30KA. Any suggestions on what to use for a Circuit Breaker on the primary side of the control transformer. I have always used a set of fuses and the circuit breakers all have a SSCR of 5 to 10 KA.

 

[zog]

You can get about any breaker with higher AIC ratings

 

[Butters]

isn't the SSCR of a breaker different then the AIC?

 

[zog]

isn't the SSCR of a breaker different then the AIC?

SCCR applies to the panel, AIC applies to the breaker, which are you asking about?

AIC applies to protective interrupting devices such as circuit breakers and fuses. The unit of measure for AIC is Amps RMS Symmetrical. This figure, which is typically in range of 5000 to 200,000 amps,describes the maximum fault current that the protective device can clear safely, without welding closed or causing damage to equipment or personnel.

SCCR applies to complete pieces of equipment or components such as dimmer racks or subassemblies such as dimmer modules. The unit of measure is also Amps RMS Symmetrical, and describes the maximum fault current that the equipment can withstand safely—or the maximum available fault current of
the feeder to which the equipment can be safely connected.

 

[richwaskowitz]

We have found that you are not going to achieve an SCCR of 30 kA without spending some serious cash for current limiting breakers with that high of a rating IF you can find them.

 

[Butters]

Thanks Zog. I guess what we need then is a 2 pole circuit breaker that has an AIC of at least 30 KA in order for my panel to have a SSCR of 30KA.

 

[zog]

What voltage? What current? What manufacturer? What sort of panel?

The 30kA is the easy part, choosing the right breaker is what you should worry about.

 

[Butters]

480vac, 6 amps, we typically use AB or Square D. This is an industrial control panel used to run a conveyor motor.

 

[zog]

OK, little outside of my area, I don't deal with much less than 1600A, but a quick look at the SQ-D digest shows a 15A 2 pole EGB has a 35kAIC @ 480V.

 

[jim dungar]

480vac, 6 amps, we typically use AB or Square D. This is an industrial control panel used to run a conveyor motor.

Both of these manufacturers should offer this type of breaker.
But it depends on voltage, AIC, mounting, and UL listing.

Have you looked at the C60 and NC offering from Square D?

 

[zog]

Was waiting for you to pop in Jim

 

[GearMan]

Both of these manufacturers should offer this type of breaker.
But it depends on voltage, AIC, mounting, and UL listing.

Have you looked at the C60 and NC offering from Square D?

As Jim indicates, the UL listing for your control panel with the proper OCPD feeding it. See link.
http://ul.com/global/eng/pages/offe...rols/industrialcontrolequipment/shortcircuit/

 

[jim dungar]

As Jim indicates, the UL listing for your control panel with the proper OCPD feeding it.http://ul.com/global/eng/pages/offe...rols/industrialcontrolequipment/shortcircuit/

Actually, I was referring to the need for a UL listing of the breaker, branch circuit or supplemental.

 

[jim dungar]

Was waiting for you to pop in Jim

Had to work today.