A universal (series commutator) motor. In construction it is a series-wound motor: the field winding is in series with the armature through the commutator and brushes. Because the current flows through both windings at once, when the supply polarity reverses both the armature current and the flux reverse together, and the torque M ∝ i·Φ(i) keeps its sign — so the motor runs equally on DC and AC (hence "universal"). It develops a high starting torque and a very high no-load speed, and is compact and light. Used in power tools, vacuum cleaners and kitchen appliances. The model shows the torque M and the speed n.
This page is a utility for simulating universal (series commutator) motor online with specified initial values.
Using the model. Close the switch to apply power — the motor takes off briskly with a high starting torque. Use the series rheostat to control the speed: universal motors are easily regulated by voltage, which is exactly how drills and mixers set their speed. The "supply voltage" slider changes the supply and the "load torque" slider the load; note how the speed shoots up when the load is removed (the soft series characteristic). The scopes show the voltage U(motor) and the current I(motor).
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