Reactors

[Grouch1980]

I came across these diagrams in an old SPD book by Cooper Bussmann. The section gives examples on how to limit short circuit currents to below that of the AIC ratings of breakers. One example is figure 5-5-12, show below. What is a reactor? And does anyone have any examples or links to a reactor?

 

[petersonra]

Reactors are inductors. They add impedance to the circuit. You don't see them used much in low voltage circuits for scc reduction because they add a lot of vd.

The second diagram is allowed but has to be blessed by UL for the specific combination of fuse and CB being used

 

[ron]

Lots of transformer manufacturers make reactors (somewhat similar product except for short circuit current reduction, most use air core rather than solid core).

What is the difference between an Air Core Reactor and an Iron Core Reactor?

Please enter sub title for Air Core Reactor and an Iron Core Reactor

americas.hammondpowersolutions.com

 

[Tainted]

It's just loops of wire with metallic cores that has reactance to help with limiting fault current. It's essentially sort of like an inductor.

Lots of transformer manufacturers make reactors (somewhat similar product except for short circuit current reduction, most use air core rather than solid core).

What is the difference between an Air Core Reactor and an Iron Core Reactor?

Please enter sub title for Air Core Reactor and an Iron Core Reactor

americas.hammondpowersolutions.com

Personally I have never seen it used in the MEP industry. Have you?

 

[ramsy]

Personally I have never seen it used in the MEP industry. Have you?

Engineers may specify xfmr impedance rather than reactors, considered later by contractors.

 

[topgone]

Engineers may specify xfmr impedance rather than reactors, considered later by contractors.

For big installations, yes. Engineers can do nothing with standard transformer impedances that are available on the shelves.

 

[ramsy]

Engineers can do nothing with standard transformer impedances that are available on the shelves.

Architects can also manipulate impedance with xfmr location, and length of feeders.

 

[ramsy]

Lots of transformer manufacturers make reactors (somewhat similar product except for short circuit current reduction, most use air core rather than solid core).

What is the difference between an Air Core Reactor and an Iron Core Reactor?

Please enter sub title for Air Core Reactor and an Iron Core Reactor

americas.hammondpowersolutions.com

Very informative. Thank you for posting.

 

[ron]

Personally I have never seen it used in the MEP industry. Have you?

We are considering using them more an more on our projects, both at the medium voltage and low voltage level. Ideally we try other methods with reactors as the last resort.

 

[Jraef]

There are disadvantages to using current limiting reactors to lower the prospective short circuit current (PSCC). One of those is that the reactance of the circuit increases, which lowers the overall power factor and puts a user at risk for PF penalties from the utility unless that then is corrected, such as with PFC capacitors, which can then have other effects on a circuit. It requires very careful engineering to balance these issues out. In other words it’s not a simple cure-all, it’s just one of the potential tools that can be employed when the PSCC ends up exceeding the equipment ratings.

I had to consider it once on an MCC project where the distributor ordered the 2,000A MCC incorrectly to where it was only rated for 42kA and the site was almost 45kA PSCC (we had wanted the MCC to be rated for 65kA). It required getting a PE involved and an expensive air core current limiting reactor that took 10 weeks lead time, but that was less expensive and faster than re-ordering the entire MCC lineup. So like I said, it’s a tool in the kit, but not a cheap or simple one to implement. (We ended up just burying some extra cable to add enough impedance and got it down to 42kA, but that wasn’t cheap either.)