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.

 The example ‘pulsing a cartridge heater in an injection molding machine’ illustrates the point; switching 60 times a minute whilst operating 12 hours a day for 250 days a year results in 10 800 000 switching operations per annum. A conventional standard contactor states a mechanical lifespan of 30 million switching operations, which corresponds to a mere three years. Moreover, the switching noise made by contactors in systems engineering applications or in processes close to where people work is often found to affect their concentration or is considered downright annoying. In such cases, Power Solid State Relays are a first-class choice as they are absolutely silent when switching. Three-phase PSSRs are utilised to control motor loads, heating systems and transformers. And the same applies here, their silent and non wearing switching functionality are compelling advantages of these Power Solid-State Relays. Both PSSR 1PH and PSSR 3PH versions are ‘ready-to-use’; that means users simply have to snap them onto the mounting rail and connect them.

 The Power Solid-State Relays offered by other manufacturers do not have this simple ‘handling’ capability. Their modules are frequently installed on the outer walls or doors of the electrical cabinets to allow the heat to dissipate better – which is costly in terms of both time and materials. In addition, this form of installation requires the use of a thermal compound – so the amount of soiling this causes is correspondingly high. Weidmüller’s Power Solid-State Relays do not need any thermal compound whatsoever. This solution means that residues, contamination and soiling have been confined to history. Weidmüller has two types of single-phase PSSRs on offer: PSSR 24VDC/1PH AC 20A and PSSR 230VAC/1PH AC 20A. And there are two variants of the three-phase PSSRs available: PSSR 24VDC/3PH AC 15A and PSSR 230VAC/3PH AC 15A.

 Each module is fitted with a green LED to indicate the operating state. Single-phase modules can operate in ambient temperatures between -30 and +80 °C, and the three-phase modules can operate in temperatures ranging between -40 and +80 °C without restriction. With Weidmüller’s PSSRs the nominal switching current in the load circuit has been rated with industrial applications in mind; the nominal switching current is based on an ambient temperature value of 55 °C. Weidmüller’s PSSR carry the CE mark; cURus approval is being prepared. All modules are suitable for extensive marking with equipment markers.