Power solid-state relays

Weidmüller’s Power Solid-State Relays (PSSR) are available as single- and three-phase versions. In comparison with contactors and standard relays PSSRs switch without any wear and are totally silent. They can cope with capacitive and inductive current spikes. With integrated zero-voltage switching, single-phase PSSRs are eminently suitable for switching resistive loads up to 20 A in 55 °C heat.

Example applications: pulsing cartridge heaters in injection molding machines manufacturing plastic components or switching infrared emitters in hardening plants or sewage works. These modules are distinguished by a low zero-voltage switching range. Three-phase PSSRs are designed with instantaneous switching functionality and are suitable for use in motor controls deployed in mechanical and systems engineering applications. Both PSSR 1PH and PSSR 3PH versions are ‘ready-to-use’; that means users simply snap them onto the mounting rail and connect them. In other words, the modules do have to be laboriously mounted onto a mounting plate or the wall of an electrical cabinet.

Power Solid-State Relays offer several advantages in comparison with electromagnet relays. They operate extremely reliably over a long service lifespan, they are compact, have low drive power requirements and extremely fast response times. PSSRs switch loads silently and bounce-free. They are insensitive to shock impact and vibration. And, in addition, they do not subject adjacent component groups to electromagnet emissions or switching sparks during switching operations. During the switching operation, the optocoupler is triggered by the control circuit. That in turn ensures the electrical isolation to the load circuit. The optocoupler output activates a power semiconductor, TRIAC or anti-parallel connected thyristors in the load circuit. An integrated suppressor circuit comprising varistors and RC combinations protect the load circuit against overvoltage surges. Power Solid-State Relays are predestined to switch higher load currents.

Weidmüller’s PSSR modules have a high peak load rating and as such have sufficient reserves to trip line-side fuses. They are capable of withstanding capacitive and inductive interference. Technical data: PSSR 1PH -> I²t = 312 A²s, 10 ms; PSSR 3PH -> I²t = 1500 A²s, 10 ms. In many industrial applications the switching capacity of electromagnet contactors is insufficient to switch loads reliably over longer periods of time. Single-phase Power Solid-State Relays are deployed, for example, to pulse cartridge heaters in injection molding machines to regulate the heating power. In comparison with electromechanical elements Weidmüller’s PSSRs do not wear out, which means they have an unrestricted operating lifespan.