The speed of innovation in electrical systems is dizzying. New components and technologies are introduced constantly, and the capabilities of systems and components is always improving
We’re beginning to see AI being deployed to improve management of electrical networks. One element of electrical networks, the relays and circuit breakers, have changed little in the last hundred years… until now.
First invented by Joseph Henry in 1835, the operating principles of electro-mechanical (EM) relay technology remain virtually unchanged. EM relays are bulky, heavy, and require a moderate current to hold them in an on-state. The switching speed of an EM relay is also relatively slow, and if switched frequently it is possible to wear out the contacts.
In 1971, Crydom Controls, a division of International Rectifier, invented the solid-state relay. Using semiconductors to replicate the functionality of a relay, these devices eliminated wear problems and offered far faster switching speeds. As semiconductors are used to pass the current, however, the resistance of a solid-state relay can be significant, resulting in cooling challenges as the wasted power is dissipated as heat. The need for heatsinking means that breakers based on solid state switches are large and heavy.
MEMS (micro-electromechanical systems) use semiconductor fabrication techniques to create tiny electromechanical devices. The technology was pioneered in the 1960s and reached widespread adoption in products we use every day including mobile phones, laptop, headphone and earbud speakers, vital signs monitoring wearables, displays technologies, airbags and many more. Now, Menlo Microsystems is introducing a MEMS-based platform, the Ideal SwitchÒ, for power products and applications.
It has long been recognised that MEMS switches have the potential to replace relays, yet the technology – particularly the metallurgy – required to ensure reliable operation over many switching cycles, has taken time to develop. The Ideal Switch is the first MEMS device that has the genuine potential to replace power control and distribution devices.
A MEMS switch delivers the same benefits as EM relays, i.e., metal-to-metal contact with negligible on-resistance that eliminates the heat dissipation problem that occurs in solid-state relays. Additionally, MEMS eliminates many of the drawbacks of EM relays because MEMS switches are small therefore consumes little power; the control is electro-static and therefore draws miniscule current to hold the switch in an on-state. This technology combines the speed benefits of solid-state relays with order of magnitude cycle-life over EM relays without the compromise of the waste heat generation, a drawback to both EM and solid-state relays.
So how are these speed, cycle-life and efficiencies realised? The chip-scaled switch is composed of hundreds of microscale switch elements that because of their small size enable them to be turned on and off in microseconds. The Ideal Switch is fast because it is tiny. Cycle-life of millions and even billions of operations is achieved because of the metallurgy on the contacts. Because the switches are tiny their mass is low and because their mass is low, they do not wear the metallurgical contacts when they close. So, they are not receiving a high amount of force or momentum to their surface. And because the switch structure is a full conductor, there is no semiconductor, its ohmic and inherently low resistance.
The MM9200, a recent addition to Menlo Micro’s Ideal Switch products, is a device designed to control 10A at 300V while being fast, high cycle life and efficient. This device can be scaled in series and in parallel to handle higher system currents and voltages. Menlo Micro recently developed a scalable control architecture for this device to support systems up to 10MW. This device and architecture are being targeted for next generation smart circuit breakers and relays. The compelling benefits of the Ideal Switch for power applications will mean that future relays and circuit breakers can benefit through more reliable, more efficient and quicker protection.
More reliable means arch-free switching. The MM9200 and its control architecture open and close electrical circuits without the drawback of an arch that degrades the contact. More efficient means conductive MM9200 ohmic contacts deliver low loss conduction versus semiconductive switching, while its miniscule size requires minimal power consumption controls. A MEMS based protection product detects line faults within microseconds and acts in the same timescale, resulting in multiple orders of magnitude reduction in fault energy going downstream to the load or the assets (e.g. industrial automation, data centre, building infrastructure assets, etc).
It’s hard to believe that such an old technology is still so important for controlling today’s infrastructure, but no one has been able to develop a suitable metal-on-metal contact solution that removes the drawbacks of legacy breakers to disrupt multi-billion-dollar markets: until now.
It might finally be time to say goodbye to conventional EM relays and breakers as MEMS will soon replace these century-old technologies with the Ideal Switch.
To learn more, visit https://menlomicro.com/
To read more from Electrical Engineering, visit https://electricalengineeringmagazine.co.uk/category/news/
