Animation: Series and shunt-wound motors

The animation shows how electric motors work and their operating behaviour. Series and shunt-wound motors are compared.

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Description

Electric motors convert electrical energy into mechanical energy. They consist of a stator (fixed part) and a rotor (moving part). Inside the motor, the stator generates a magnetic field that causes the rotor to turn.

In reality, two parameters of an electric motor can usually be changed directly: the speed and the torque. Speed and torque influence each other. If a drill is pressed against a workpiece, the torque increases and the speed decreases.

The relationship between speed and torque varies depending on the design of the motor. The motor type (series connection or shunt connection) has a major influence.

Series motor: Here, the armature and the excitation winding are connected in series. These motors offer a high starting torque and are often used in applications with variable loads, such as electric trains.
Shunt motor: The armature and the excitation winding are connected in parallel. These motors offer a constant speed and are often used in applications with a constant load, such as fans or pumps.

In principle, the torque of a motor is proportional to the power consumption. The following formula applies to all electric motors:

The parameter c is a constant specific to the respective motor. The performance of the motor can be read from the constant. It is an important manufacturer specification. The flux Φ is a physical quantity that describes the magnetic field in the motor.

The internal resistance of a motor influences the power consumption and therefore the torque. A lower internal resistance leads to a higher current consumption and consequently to a higher torque.

The internal resistance not only depends on the conductor material (ohmic components), but can also change during operation (inductive components). The cause of this is counter-induction. Induction occurs when conductive materials are exposed to a moving magnetic field. At a low speed, this effect is minimal.

The following formula is an extended version of Ohm’s law, which takes into account the influence of the internal resistance of a voltage source and the external resistance in the circuit.

A series-wound motor is an electric motor in which the armature and the excitation winding are connected in series. The resistance increases with increasing speed, as the current flows through all the resistors one after the other.

In contrast, in a shunt-wound motor, the armature and the excitation winding are connected in parallel. In a parallel circuit, the increase in resistance generally has less of an effect on the overall resistance of the circuit. This means that a shunt-wound motor still draws sufficient current even under heavy load.

The different characteristic curves result in different behaviour and different areas of application. For a train, a slow start (high torque and low speed) is definitely desirable. For a pump, it may be important to maintain a constant speed even under load.

Overview and download

TitleSeries and shunt-wound motors
Target groupTeachers and lecturers
PlatformsMicrosoft® Windows®
Apple® Macintosh®
FeaturesFull screen mode
lossless zoom
Large screens and projection screens supported
LicenceFreeware
DownloadContact us

Contributors

C. Hein, S. Rikowski

Source information

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