Industrial Motors Got More Efficient In 2012

Dec. 13, 2012
Paul Schimel reviews the year's progress for industrial motors.
One of the most memorably egregious applications of electricity that I recall occurred at Roy’s farm, about two hours outside of Chicago. It was harvest time. Roy worked a lot of ground and had lots of grain bins. Those grain bins had fair-sized blower assemblies and motors to circulate air through the grain and bring down the moisture content.

I was finishing up some wiring in his garage with my dad. We were adding drops, subpanels, and disconnects for a welder, air compressor, and large drill press. Roy wired things differently than we did. We were concerned with things like safety, service disconnects, fusing, bonding, ampacity, conduit fill, and keeping moisture out. Roy didn’t share these concerns.

We were about done in the garage when my dad said something to the effect of “you won’t believe this!” I hurried over and saw Roy, a tough old dude, walk over to a 120/0/120-V lineset that fed the motors on the grain bins. It was a hefty lineset, probably 2 or 4 AWG, with three conductors, one of which was bare (neutral).

The junctions he needed to access were lying in a puddle of water, and of course, they were open and live. So Roy walked into the puddle, grabbed the connections, and got to work—without any personal protection equipment (PPE) or anything resembling electrical insulation. The connections had no wire nuts or other means to keep out moisture. Leakage apparently wasn’t a concern, nor was there a ground fault circuit interrupter (GFCI) within a few miles of Roy’s place. The safety offered therein would simply be a nuisance.

There was a break in one of the hot legs of the line set. So Roy took out his non-insulated cutters and stripped the ends of the cable (still standing in the puddle). Then he twisted up the connection, again, bare-handed, still live, dropped it all back in the mud puddle, and walked out (Fig. 1). I was flabbergasted. Having made a few mistakes fixing TVs and radios at that age, I was absolutely certain that the whole experience had to have been painful—and it could have been far worse than painful.

1. Don’t try this at home! There is a right way and a wrong way to splice the wires to the blower on a grain bin. This is the wrong way.

Sometime later, Roy walked over and thanked us for our work, paying compliment to how well everything was set up, piped, protected, and bolted down. I asked him if splicing those conductors bare handed with uninsulated cutters while standing in a mud puddle hurt at all. He smiled a guilty smile and said that it did, but he does that sort of thing all the time and was used to it. Absolutely wild! I simply can’t imagine, nor should I. What Roy did was wrong on many levels, yet he didn’t think so. He’d been doing it that way for 50 years.

More Efficient Motors

Looking back on 2012, I’m reminded of watching old Roy twist up those conductors in the 1980s. Locally, 2012 was not the best year. I saw a lot of smaller shops and businesses shut down. I watched a lot more folks walk away from houses, a lot more bank foreclosures, and a lot more hearsay on when and how it will all get better. Just like standing in a puddle twisting large energized 120/0/120-V ac conductors together bare-handed, we know both practices to be unhealthy and painful. In spite of that economic nastiness, I did see some good innovations that are well worth mentioning.

There seems to be a big movement underfoot to build more efficient motors in virtually all applications—something that’s been long overdue. This movement is finally forcing a look away from the long-exploited squirrel cage and/or dc brush motors, as well as bringing gearing, mechanical power transfer, and hydraulic power transfer into question. These are all good things.

I've seen Electric Vehicle Technologies (EVT) of Fairbury, Ill., continue with its tireless efforts and breakthroughs on scalable, low-speed, high-torque innovations. These machines are ideally suited to hub applications in over-the-road and offroad vehicles. They require no gears and deliver phenomenal torque into, out of, and at stall speeds. EVT offers the highest torque to weight ratio that I've seen, likely the highest of record.

In the media, these innovations don’t make a sensational splash like a new iPad. In application, however, if that new mining truck or wheel loader can do the same work for half the fuel, it’s a significant game changer. And at the dynamometers, when the efficiencies come out to something near ideal at counter-torque arm bending or load-cell saturating torques, these machines are truly breathtaking.

The gains in fuel economy and reliability will triumph as the vehicles are redesigned with engine/gensets, battery banks, and distributed electric power instead of mechanical power or hydrostatic power, and/or intelligent drives and innovative motors to do the work and move the payloads. These vehicles will utilize not only lots of power electronics in all drives and dc-dc converters, but in the battery and battery management system, too.

The added battery banks will serve as energy storage for peak loads and perhaps regenerative propulsion management. Great opportunities are in store for power switches, wide-bandgap semiconductors, drivers, health monitors, and control engines.

At Milwaukee Electric Tool, the cordless design team launched the Fuel platform of permanent-magnet (PM) brushless cordless drills, which can drive more screws, drill more holes, run cooler, and last longer than their predecessors. The machine oozes with innovation and puts out enough torque to require a secondary handle—even for the toughest, most work-hardened wrist. The motor is a pretty straightforward three-phase machine with excellent efficiencies. Clearly, though, there are some power electronics and controls needed to go beyond the classic single-switch chopper. This is a rough-and-tumble application where rugged MOSFETs and high/low-side drivers are a must-have.

In the refrigeration arena, I’ve seen many innovations emerge that exploit brushless PM machines in compressors. In general, a basic refrigeration circuit has a hot side and a cold side (Fig. 2). The cold side will experience a pressure drop—an orifice or capillary-type expansion device feeding an evaporator coil. The superheated refrigerant from the evaporator coil then flows into the condenser circuit.

2. A basic refrigeration circuit has a hot side and a cold side. The cold side will experience a pressure drop—an orifice or capillary-type expansion device feeding an evaporator coil. The superheated refrigerant from the evaporator coil then flows into the condenser circuit.

The first part of this circuit is the suction side of a compressor. The compressor’s output then forces the refrigerant into a large coil to exchange the heat added in the evaporator with the outside environment. The condenser coil’s output becomes liquid that’s pumped to the expansion device, closing the loop.

As legislation or utility pressure (hand in that old fridge and buy new—we’ll even haul that old one away for you!) drives coefficient of performance (COP) or Seasonal Energy Efficiency Ratio (SEER) requirements higher and higher, the compressor motor must be reexamined. Several companies have done this successfully.

Brushless PM machines are now found in many compressor motors as well as fans and blower motors. These compressors, fans, and blowers require three-phase variable-frequency drives for variable-speed control. Hats off to that innovation! Bravo! A welcomed improvement! The net effects of having near continuously variable transfer rates at the condenser and evaporator have yet to be fully exploited. However, they will be soon enough, and the energy savings will be substantial.

While 2012 may not have been the most prosperous, I’m thankful that the innovators didn’t rest on their laurels or stick their heads in the sand and wait for things to turn around. These machines will serve us well in some near future. I think it’s more a matter of usefulness than flash or bling. I prefer to know that payloads were being moved and transported more efficiently, versus a new phone app that offers more useless games, navigation, and virtual doo-dads. These machines will boost performance and reliability, as well as save cost, thanks to net efficiency gains. Maybe in 2013, we’ll all be able to afford some of them!

About the Author

Paul Schimel | Senior Field Applications Engineer

Paul Schimel is a senior field applications engineer at International Rectifier. He has more than 15 years experience in power electronics design, EMC, and transformer design including offline ac-dc converters for medium and high power levels, motor drives, and dc-dc converters. He is a hands-on engineer and innovator, endlessly building power electronics circuitry, welding, and machining for audio, HVAC, and propulsion applications. Also, he is a licensed Professional Engineer and holds two patents. He can be reached at [email protected].

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