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I live in the US and recently bought a home. There are several electrical outlets in my garage. I have recently had two tools that have burned up and gone to an early grave. It turns out that the previous owner put in a 220 volt outlet but used a 20 amp 110 receptacle. I figured this out after my shop vac motor burned-up and died. Also, my belt sander emitted sparks, flames, and died. A quick check with a multimeter determined that some goof ball put 220 into a standard outlet designed for 110v.

Of course, I will be wiring this outlet correctly. For now, it is covered with tape.

So, here is my question. Some tools, like my air compressor and table saw were not damaged by this outlet. I used the outlet for these tools and they don't seem like they were harmed. Why did some tools die and others survive ? ? Is it a difference between brushed and brushless motors ? ?

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    Have you traced the line back to the circuit breaker and confirmed that it's using a two pole breaker? – The Evil Greebo Aug 2 '13 at 13:17
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    There's usually a label near the plug that indicates the voltage tolerances of the device. Many are designed to work with anything from 100v to 240v to make international sales easier, but not everything as you've seen. – BMitch Aug 2 '13 at 13:17
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    You might consider getting an electrician in for an inspection. Tell him what this genius did, and that you don't trust anything anymore. – Chris Cudmore Aug 2 '13 at 13:22
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    Oh man. I think you'd being generous with the term "goof ball". – Hank Aug 2 '13 at 14:04
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    It's as bad or worse than the "Retired Fire Chief" that lived across the street. He had no compunction against punching holes in the sheet rock and running extension cords through the walls to make improvised remote outlets for all the kitchen cabinets. And another nasty with the breaker panel, similar to yours. Verboten. – Fiasco Labs Aug 2 '13 at 15:29
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Many devices are rated for either 110 or 220. There should be a tag on the device which says this. In some appliances its done intentionally so that one model can be sold and safely used in countries which use either voltage. In other cases its simply dumb luck that the component parts can tolerate either voltage.

I'm not sure if this fully answers your question. "The device is rated for it" doesn't really cover what aspects of the device make this possible.

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    Usually motor driven tools require rewiring to change the voltage. Universal input voltage is used on switching power supplies for smaller loads like lights & computers. – Ed Beal Dec 27 '18 at 20:32
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It's not going to be about brushed vs. brushless motors but the quality and grade of the parts used in the tools. Heavy duty equipment like a compressor or table saw are likely to use heavier wiring and components which can take the higher voltage, where the lighter weight tools are overheating with the voltage they weren't designed for.

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    Until the overheating later lets out the magic smoke. – Fiasco Labs Aug 2 '13 at 15:30
  • It is how the field windings are connected, with the windings in series they can handle 240 in parallel 120, usually if a motor is wired 120 if you connect it to 240 it will fry the motor on standard AC induction motors. – Ed Beal Dec 27 '18 at 20:37
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You'll probably get a better answer on physics or electronics, but it's mostly a matter of voltage and damage not being that simple, especially when there are magnetic fields involved.

More voltage will drive more current through the same circuit. More current generates more heat. What happens from there depends quite a lot on exactly what the circuit is and the physics of any moving parts.

In the case of your drill and belt sander I would guess that what burned out was most likely the speed control. Speed controllers use semi-conductors to flip the power on and off with the cycles of the AC current. Semi-conductors (Silicon Controlled Rectifiers in this case) really don't like being subjected to voltages higher than they're rated for or excessive heat and tend to melt, explode, catch fire, or do other, violent things in response.

Your table saw and air compressor don't have speed controllers though. So if you subject them to a higher voltage, that drives more current, but nothing immediately faults and burns up. The more current results in more heat, but also creates stronger magnetic fields inside the motor. The stronger magnetic fields spin the motor faster. The motor spinning faster makes its fan push more cooling air. It's not actually that uncommon for motors to run cooler at higher voltages with the same load because the field effects are more efficient and the higher speed cools them off better. Couple that with most of the larger tools' electric motors being designed to run at either 110 or 220 because that makes them significantly more useful for an insignificantly higher cost and it's not terribly surprising that your heavy-duty tools could handle the higher voltage.

In fact, you might want to consult their owner's manual and/or the spec sheet of the motors they contain and see about just switching them over to 220v permanently. If they were designed to to that they'll run cooler and last longer plus they'll use the electricity more efficiently so it will cost you less to operate them, and you already have 220v available, you just need to put a proper socket on it.

  • Most AC motors require a wiring change to change from 120-240 although I agree that the SCR's or triac's used for speed control don't like voltages above there ratings. I have had friends hook up motors wrong and usually if the motor was wired for 120v and connected to 240 they will smoke in a very short time. – Ed Beal Dec 27 '18 at 20:43
  • @EdBeal And if they're wired for 240 and you apply 120 you can also smoke them sometimes when they don't spin fast enough to stay cool. It really depends on the exact design of the motor and precisely what the load is. There are even some types that won't smoke on too-high voltage, but will over-rev to the point where they undergo a "rapid, unplanned disassembly" if the load is insufficient. I've seen a couple really old ones from before electrical service was well-standardized that, according to the plate, could run on anything from 90v to 250v, AC or DC. There's lots of variation in motors. – Perkins Dec 27 '18 at 21:04
  • I would agree that DC motors have a huge range. But AC motors do not I work on everything from fractional horse power motors to up to 1200 hp on at least a weekly if not daily. Most AC motors have specific voltage ranges dual voltage motors require rewiring to change the voltage running any motor outside its wired configuration can dammage any motor but it is more likely to have almost instant death of the motor by applying the higher voltage when the windings are in parallel, series windings with lower voltage would never be instant death because the reactance will be less. – Ed Beal Dec 27 '18 at 23:48
  • @EdBeal It would be interesting to know what models of motor were used in the surviving tools. I've seen air compressors which have a voltage selector switch to handle the wiring change. I wonder if there are models now that do it automatically. It's probably either that or a motor design that prioritized robustness and flexibility over price and efficiency. – Perkins Dec 28 '18 at 22:14
  • In this case I agree but most AC motors require some change in wiring a switch on the motor could do this so I have no problems with this comment. – Ed Beal Dec 29 '18 at 1:34
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Because over voltage tolerance is a complex matter and the susceptibility of any individual device is highly dependent on the design of that particular device.

Into a resistive load twice the voltage means four times the power. Depending on where that heat goes that may or may not be enough to make the device go up in smoke but there are many other effects that can either mitigate or worsen the effect. On the worsening side we have.

  1. Magnetic saturation. If too much energy is stored in an iron-cored coil the core will saturate and the effective inductance will fall through the floor. If the device was relying on the inductance of the coil to limit current this can result in a massive increase in current.
  2. Electrical breakdown. High voltages can rip electrons off atoms which can then start conducting leading to high currents where there were not supposed to be high currents. Normal wire insulation will not break down with a mere 2x overvoltage, but electronic components like diodes, transistors and capacitors may well break down at this level. Electrical breakdown can also happen with deliberately-placed spike protection devices that were designed to break down and shunt away short spikes of overvoltage, but were not designed to handle sustained overvoltage.

On the mitigating side we have.

  1. Some things self-regulate. A motor (if it has not suffered from magnetic saturation) will draw less current as it's speed increases. A device with a thermostat will heat up quicker but assuming nothing breaks down the thermostat will mean the final temperature ends up approximately the same as normal.
  2. Some devices have protection that will trip out under over-voltage or over-temperature conditions. This protection may or may not be self-resetting and it may or may not act fast enough to save the device.

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