CHAPTER 7 - SOLID STATE RELAY

INTRODUCTION OF SOLID STATE RELAYS

     First, I will explain the general overall before go to solid state relay (ssr). It comes from electromechanical operated switches which are triggered with the use electricity. There are three types of electromechanically operated switches: relays, solenoids, and semi-conductive. So what is relay? Relays are electromechanical devices that either use a small input voltage (24v) to control a larger output voltage (230/460v) or use an input voltage to control two or more output voltages.

Definition:

     A SSR (solid state relay) can perform many tasks that an EMR (electromechanical relay) can perform. The SSR differs in that it has no moving mechanical parts within it, it is essentially an electronic device that relies on the electrical, magnetic and optical properties of semiconductors, and electrical components to achieve its Isolation and relay switching function.

     Over the last ten years many standards have been set regarding SSR packages, most notably the rectangular package introduced by us in the early 1970s which has now become an industry standard for power switching using SSRs, with models ranging from ito 125 A.

Applications:

     Since its introduction the SSR, as a technology, has gained acceptance in many areas, which had previously been the sole domain of the EMR or the Contactor. The major growth areas have come from Industrial Process Control applications, particularly heat/cool temperature control, motors, lamps, solenoids, valves, transformers. The list of applications for the SSR is almost limitless.

     The following are typical examples of SSR applications: manufacturing equipment, food equipment, security systems, industrial lighting, fire and security systems, dispensing machines, production equipment, on-board power control, traffic control, instrumentation systems, vending machines, test systems, office machines, medical equipment, display lighting, elevator control, metrology equipment, entertainment lighting.


The Advantages of SSRs:
• Zero voltage turn-on, low EMI/ RFI
• Random turn-on, proportional control
• Long life (reliability)> 19 operations
• No contacts — handles high inrush current loads
• No acoustical noise
• Microprocessor compatible
• Design flexibility
• Fast response
• No moving parts
• No contact bounce

References:

Petruzella, Frank. 1996. Industrial Electronics. Mc-Graw Hill. Singapore