That is not news I want to hear.
This goes for running 230VAC single phase on 208VAC single phase service?
I had always thought there was some lattitude in voltage ratings of motors.
Can anyone elaborate on why this would cause overheatng/shorting? Trying to
learn something along the way.
There is some latitude. A nominal 230 motor will typically run fine on
voltages between 220 and 240. But 208 is too low unless the motor is
specially designed to handle it. Horsepower is voltage times current
divided by 746. For a given horsepower demand, a lower supply voltage
means the motor must draw more current to provide rated power.
Heat build up in the motor is a function of current squared times winding
resistance. So the more current the motor has to draw to meet the load
power demand, the hotter the motor will run. Notice that heat is a function
of the square of current, so it doesn't take a whole lot of excess current
to get the motor very hot.
Motors are designed for a specific maximum temperature. Exceeding that
temperature will greatly shorten the life of the motor, ie you'll let out all
magic smoke if you persist in running a motor at its rated output power
with lower than rated supply voltage.
Note that you could probably get away with running a 230 volt motor at lower
than design voltage if you don't draw anything approaching its rated power
output from it. In other words, if the motor is oversize for the load power
demand, it'll tolerate running on a lower voltage. That's how motors rated
to run on 208 to 240 are designed, ie they're bigger (larger windings and
or more cooling air) than their nameplate hp would otherwise require them
to be. That costs money, so equipment manufacturers typically don't use
such motors unless you pay extra for them.
If you want to operate a 230V motor on a 208V supply, you must add a
buck-boost transformer to the system.
By definition, a motor must be able to operate at +/-10% of nameplate
For a 230V motor, that translates to 207V minimum which sounds like it might
work on a 208V supply; however, the utility supply voltage is allowed to
operate at +/-10% which translates into 187V minimum.
Therein lies the rub. You can't get there from here.
Add a buck-boost x'fmr.
They are small and relatively low cost.
S/A: Challenge, The Bullet Proof Boat, (Under Construction in the Southland)
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