What is a shunt current

Universal motor


Standard universal motors have an output of up to 3kW. There are speeds from 3,000 rpm to 30,000 rpm

The operating behavior with alternating current changes only slightly from direct current operation. The high starting current and a strongly load-dependent speed are normal.

Universal motors are very loud when in use and the coals wear out quickly, which is why they are used for devices that run for long periods of time, such as B. Cooling devices not used. The speed can be reduced by the voltage or by phase angle control.

Field of use:

• In almost all household appliances (e.g. vacuum cleaners)

• In power tools (e.g. hand drill, jigsaw)

• large single-drum motors (e.g. wheelchairs)

• Powerful universal motors are also used in locomotive motors


If the direction of the current is reversed in a series motor, the direction of the armature and excitation field changes. However, the direction of rotation remains the same. For this reason, a series motor can be operated with direct current and alternating current. In order to avoid eddy currents, the armature and the stator must be layered from insulated sheet metal, whereas in a pure DC motor the stator can consist of solid iron. The universal motor may only be operated under load, otherwise the rated speed is too high and the motor would be destroyed. Since universal motors, like all DC motors, have a collector and carbon brushes that generate radio interference when they are running, they have to be equipped with suppressors made of capacitors.

Motor nameplate

On a standard nameplate for a universal motor (see picture) everything important for connecting a universal motor is written on it. Electric motor Rated voltage: 220V ~ Rated current: 0.48A Output: 55W Manufacturer: EMW Grosschopp u. Co Type number: 1702260s (nameplate of a universal motor)

common causes of failure

The most common errors that occur and cause the engine to stop working are the following:

Wear of the carbon brushes

Due to the spark formation on the carbon brushes, they have a very high level of wear. These can be exchanged very easily, which should make the engine work again.

Dirt in the armature windings

Due to the wear and tear of the carbon brushes, dirt very often collects in the armature winding, which can be removed again with a knife.