What Is Short Circuit Current Rating?


Hi, I'm Dan Bender, and I'm the Director of Sales for Control Concepts, Inc. Today I want to talk about Short Circuit Current, and Short Circuit Current Rating. 

First, what is Short Circuit Current? Well, it's the available fault current in the supply lines that are feeding branch circuits that have power conversion equipment, such as SCR power controllers and other devices. 

Short Circuit Current Rating is the manufacturer's description on their nameplate of the maximum fault current the equipment can withstand, when properly installed with the appropriate overcurrent protection devices. 

How does this impact companies? Many companies will have a governing body that will establish a Short Circuit Current Rating. Typically, this is 65kA or greater. The intent of this is for personnel protection, lowering insurance rates, and meeting specific codes such as NFPA 70E and UL 508A Supplement SB. 

This is becoming more and more common, and unfortunately all too often, people are finding out about it at time of installation. The time to be discussing this is during the design criteria. 

You must be aware that the "weakest link" is the situation we have to be concerned with. For example, if a piece of equipment has a 65kA rating, and another device has a 5kA rating, the entire circuit is based on the weakest link – in this case, 5kA. 

It's all about safety. What we have here is your potential for a fault current that can cause an arc flash, and that means that individuals who are responsible for working on this equipment now have to wear protective clothing. This protective clothing is expensive, and it is cumbersome. Furthermore, if there is arc flash, there is potential for someone to be seriously hurt, or something even more catastrophic.

Just adding branch-rated fuses may or may not meet this criteria. That's where Control Concepts can help you out. Our equipment has a 100kA Short Circuit Current Rating. You can go to our website and find out more information about that. In fact, you can watch a video of the actual Short Circuit Current testing

There has been some confusion about SCCR and Interrupt Capacity. These are two totally different things. You can go to our website and find more information about how these are different.

In wrapping up, the purpose of this is to give you some information about Short Circuit Current Rating and how you can find information to help you design a system that is safe for your personnel. Thank you.