Author Topic: Anyone Here Fluent On Antique (100yr.) Electric Motors?  (Read 611 times)

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Anyone Here Fluent On Antique (100yr.) Electric Motors? « on: November 25, 2017, 05:06:58 AM » Author: Steele1992
Just got a antique vacuum that's pretty much a century old, and I wanted to know if anyone here is fluent on electric motors of that vintage. The motor is only 1.5 amps and 110 volts, and I wanted to know if that can be run today on a modern home by just plugging it into your outlet? That it won't burn up or anything.

  I read that in these old days, they built vacuums with this low energy usage because most rural farms ran on battery power and were not connected to the grid yet because it was so remote. The vacuum came from a small Amish community in Wisconsin (1,400 people) so it definitely is a pretty old find.

I know it will need a new cord and a full strip and clean, but just wanted to make sure about the electrical rating first before I proceed.   :inc:

Here's an example of a 1920's Delco farm generator.

and you would hook a battery rack like this one up to it, and that was your power.
« Last Edit: November 25, 2017, 05:11:29 AM by SeberHusky » Logged

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Re: Anyone Here Fluent On Antique (100yr.) Electric Motors? « Reply #1 on: November 25, 2017, 05:58:44 AM » Author: Ash
Most vacuums today use series connected brushed motors (the armature, which is connected through the brushes, is in series with the field winding). Main reason is, that they can reach very high RPM at low torque, which means fast air suction. The series connected brushed motor existed and haven't changed much since the days of Tesla and Edison, so in all likelihood, the same motor is used in this vacuum as well

But open it to double check anyway

Series brushed motors generally work on both AC and DC, therefore this alone does not tell us whether the vacuum was designed for AC or DC. But depending on the motor design, it may be built with only one of them in mind. Using it on the wrong supply may be a problem :

Using AC motor on DC supply :
 - Saturation of the field winding, causing an overcurrent and increase in RPM
 - Excessive arcing at the brushes

Using DC motor on AC supply :
 - If the field core is made of single block of metal instead of laminations (as it is in some DC motors), it will be very lossy and might overheat
 - Otherwise, it would be fine as long as the AC peak voltage is equal or less than the rated DC voltage. But this would mean much lower power
 - Running on higher AC voltage (where the RMS equals the rated DC) means 1.41x higher flux density in the cores than was intended. This can be ok as long as the cores dont saturate, which depends on the safety margin with which the motor was designed

If it cannot be determined whether it was intended for AC or DC, but the field core is made of laminations, the safest way to see that it works at all would be to try running it up with a variac, up to 110/sqrt(2) = approx 80V RMS (110V peak) AC, and not load it mechanically to the point where it would stall (unlikely with a vacuum). Monitor the temperature and see that it does not overheat. This would be much less than full power though

As with any such device, inspect its insides and check the mechanics (everything moves freely, bearings oiled, nothing hits or grinds anything) and electrics (isolation, brushes) before attempting to power up
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