Cooling Considerations for CLR’s in NEMA 3R Enclosures
Docta Reacta: Current Limiting Reactors, also known as CLRs, are most frequently sold in NEMA 3R enclosures and used in some pretty demanding environments, usually coal fired power plants.
First, let’s discuss clearances for the enclosure. In this case, clearances for reactors within enclosures are dictated by the voltage class, not cooling requirement. For 600 volt class, one inch of clearance is all that is required.
Cooling considerations dictate ventilation openings. For natural convection cooling, it is desirable to have one square foot of unrestricted opening (for both air inlet and outlet) per kW of loss. For a current limiting reactor, or CLR, with two kW of loss, two square feet of opening for inlet and outlet each is needed.
Forced cooling is a separate consideration and calculation based on CFM and temperature of the air supply. This condition is rarely present in these applications.
This is the short and sweet but should answer your basic questions about cooling current limiting reactors in NEMA 3R enclosures.
If you have any questions, please leave a comment or give us a call.
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