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"Three-Phase Solid State Relays and their Application in Three-Phase Heating Circuits"

Precision in Heat Control Starts with the Right SSR

Solid State Relays are used in a wide variety of electrical load-switching applications, including Professional Cooking Equipment, Plastics Machinery, Packaging Machinery, Lighting Systems, Medical Equipment, Laboratory Ovens, Beverage Dispensing Equipment, HVAC&R systems, and many other industrial or commercial applications. However, for the purpose of understanding these applications relative to the use of SSRs for their control, most loads can be grouped into two primary categories: heating and motion control.

Obviously, this is not an all-inclusive grouping as there are other applications outside of the scope of these two categories such as lighting and power distribution systems. However, most Design Engineers specifying SSRs apply them to one ofthese two general types of three phase loads. The focus here is on heating loads while a companion paper focuses on motor loads.

While every application is different and requires its own scrutiny, focusing on these two main categories allows us to generalize about the characteristics of the applications and the subsequent requirements placed upon the SSRs used to perform the switching functions for each. Moreover, limiting the focus to higher-power systems utilizing three phase networks to energize the load(s) covers some of the most demanding commercial and industrial applications where SSRs are used today.

This paper includes a summary review of three phase power systems, the characteristics of common three phase heating loads, and a comprehensive discussion of three phase SSRs and their application relative to such loads.

What you will learn: