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Multi Purpose Rotary Machine - Mulling, Welding, Pottery, Photography Turntable

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Step 14: Using a Washing Machine Motor (Series Wound or 'Universal' Motor)

Picture of Using a Washing Machine Motor (Series Wound or 'Universal' Motor)
motor test rig.jpg
washing_motor field windings.jpg

There are plenty of other kinds of motor types that could be used for this project, some would probably be better choices, but since I am in charge here, and I have (and you should be able to get your hands on) a spare washing machine motor or two - that's what we are talking about.

A theoretical, loss free series-wound motor, supplied at constant voltage has the characteristic of slowing down when load is applied at the following rate: The shaft speed halves, for every quadrupling of the load. Think about that a moment, it becomes important!


1. The speed goes down (quite a bit), and varies depending on load - that's a pain if we want constant rpm, while we are mixing sand, rotating a welding workpiece or manipulating clay, for example.

2. If we have no load at all on the shaft the speed would rise - without a theoretical limit! In actuality on large high speed motors like washing machine motors, the limit can be the rotating armature having its ass kicked by centrifugal forces, and coming apart (bad - see warning below).

Identify the connections

Armature (between the brushes) should be easy - two connections and roughly 2 ohms. The value will vary slightly depending on how the brushes are sitting on the armature, so rotating the motor shaft slowly will likely change the value.

Series field winding ~ 2 ohms

AC Tachometer ~ 180 ohms

Over-temperature protection 2 contacts ( often read 0 Ohms, but depends)

The motor frame earthing point

Test the motor with a 12V bench power supply (briefly). Or by putting a 1kw heating element in parallel with the armature (see diagram).

Warning: do not connect the motor unloaded to its rated voltage. It probably won't survive, and in worst cases could fling shrapnel at you.