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ADVERTISEMENT FEATURE COVER STORY


POWER RELAYS: THE NEW CONFIGURATION Switching high loads on PCB is becoming simpler than ever before, says Panasonic. Here’s more on why?


I


n recent years the electromechanical relay market has more than adequately produced PCB switching devices for higher ac or dc voltages with most of the producers offering a very wide range in terms of cost, physical size, contact and coil specification. However the ubiquitous 16A current contact switching is rapidly becoming a limiting factor, especially in the area of high current PCB design, and there is now a compelling need for relays with a much higher breaking capacity. Of course alongside this target there is an aim is to achieve higher packing density and smaller size without any significant compromises in key relay characteristics. Panasonic Electric Works is a leading


electronics company in electromechanical switching technology, combining the new sophisticated PCBs with the modern “power relay” portfolio and introducing the idea of switching high loads on the PCB itself. As designers will be aware there has been an impressive development in the field of PCB technology. New multilayer circuit boards, high power connectors and advanced materials are just some of the innovations that have been introduced. PCB mounted electromechanical relays are used in many cases to control the high load, instead of having other electrically controlled switches installed in cabinets or other suitable locations. The relay is no longer used as the component responsible to switch a few amperes in order to control the secondary contactors but rather they are now used as the key element for making or breaking of the final load. The relay in isolation, or in conjunction with other semiconductor components, ensures secure electrical isolation and long life performance.


HIGH SWITCHING CAPACITY As an example in the recently developed HE power relay series the relative switching capacity, which is defined as the highest switching capacity of all contacts under specified conditions relative to the volume of the relay and considered a reliable indicator of the development trend in general, has been boosted significantly. Crucial considerations for development


included not only size requirements but also the requirement for minimal energy consumption. Much attention has been


12 NOVEMBER 2018 | ELECTRONICS


dissipation can be achieved externally by powering the coil from a pulse width modulation drive source. A long pulse width is applied to the coil on initial energisation to achieve reliable and fast contact operation. However once the relay contacts have been made, the pulse width can be reduced to a much lower level. This results in lower heat generation and lower energy consumption and this in turn leads to a situation where a ventilation hole arrangement in the majority of the cases is not necessary. Internally a galvanic separation of


focused on coil power dissipation while power dissipation through the contacts has also been significantly improved. Relays in the HE series, while being


certified to relevant UL & VDE standards, are able to handle loads up to 120Amp and 1000VDC with ambient temperatures up to 80°C. To allow use in many parallel markets, such as in the replacement of traditional contactors, it is possible to have the option of an auxiliary contact for monitoring and feedback purposes. In use the HE-S relay version is able to accommodate this requirement with its 2 form A + 1 Form B mechanically linked contact configuration. This feedback contact is offering a


major advantage in its ability to allow an external circuit to monitor the condition of the main contacts with non-operation or welding easily identified. This is a major asset in many advanced designs circuits where widespread use has proven the HE relays abilities. Although already highly efficient a further improvement in coil power


Figure 1:


The HE power relay series from Panasonic


minimum 3mm along with high creepage and clearance distance guarantees high insulation resistance, high dielectric strength and protection against surge voltages. A mechanical life of minimum 1 million operations assures a problem-free service life, while the low contact resistance that is usually in the area of mΩ ensures extreme low power dissipation. In combination with the reduced operating power this directly contributes to equipment energy savings. The new high power PCB relays have been designed to accommodate coil power reduction from first switch. This results in an initial low contact resistance and high contact pressure. Having the switching power on the


Figure 2: The relay development over the years


PCB and using power relays saves from other electrically controlled switches and the associated expenses both financially and in energy consumption. In most of the cases the control cabinet is no longer necessary. The advantage is in this case is obvious in no external wiring, reduced installation expenses, small size, reduced thermal loses, flexibility and one single working point. The extended Panasonic portfolio of


HE power relays can cover many of the modern requirements and deliver added value to the final customer. In many application areas, such as frequency or solar inverters, battery chargers, automotive charging stations, the switching function has already been moved to the next generation.


Panasonic Electric Works UK www.panasonic-electric-works.com/uk T: 01908 231555


/ ELECTRONICS


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