Look Ma… No More (added) Wires!

I firmly believe that at some point, 100% of all electric motor power will pass through at least one semiconductor. Most, if not all will be under microcontroller control and will be able to communicate with the outside world. But just how will that be done? Last month I touched on the software side of this question. This month I’d like to address the physical side of motor communication. Up till now, the needs and resources of stationary industry dictated motor communication evolution. Until around 1980 hardwired analog approaches dominated. Then came RS485 and various digital schemes that used existing 4-20ma process control loops. More recently, Ethernet and wireless schemes like Zigbee and even WiFi have been used.

But will these be dominate or even be appropriate as controlled motor systems move down the food chain, replacing motors in diverse direct grid connected applications like commercial, agricultural, or even residential HVAC and pumping? Penetrating many of these markets will require near drop-in replacement of the existing approach. Wireless techniques, particularly Zigbee will certainly find a home, but another much older technique is gaining favor.

Power Line Communications has been around since 1922 when analog carrier frequency systems began to operate in the 15 kHz to 500 kHz range for telemetry and in the 1970’s X10 made its appearance for simple on/ off control. More recently, in 2011 the G3-PLC Alliance was formed to promote the G3-PLC protocol, which, in the US, operates at 155kHz to 487 kHz and provides the low level protocol for large scale infrastructure on the electrical grid.

These PLC systems are not broadband and are not intended for streaming Netflix. That was tried in the mid 2000’s as Broadband over Power Lines or BPL which proved to be a commercial failure.

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