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Commutator: An Introduction

Last updated date: 31st Mar 2023
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The use of DC devices for daily necessities has become a normal occurrence in our lives. DC generators and DC motors are two different types of DC machinery. DC generators turn mechanical motion into DC power, whereas DC motors turn DC electrical power into mechanical motion. The problem is that a DC generator produces AC current, even if its output is DC. Similar to how it applies when the power delivered to a DC motor is DC, the concept of the motor still holds true when the current in the coil alternates. So, how are these devices operating? The little gadget known as the "Commutator" is the solution to this puzzle.

What is a Commutator?

A group of bars or segments connected to the armature coils of the generator or motor to convert alternating current into direct current when the generator or motor turns.

Why is a Commutator Needed in Motors and Generators?

A motor's windings get an electric current from a commutator. By switching the direction of the current in the spinning windings every half turn, a constant rotational torque is generated. The commutator of a DC motor is made of copper.

A commutator in DC generator is used for the purpose of converting the alternating current from the generator's windings to unidirectional direct current in the external load circuit, the commutator inverts the direction of the current with each turn acting as a mechanical rectifier.

What is a Commutation?

In DC machines, the process of reversing current is known as commutation. The function served by the commutator of a DC generator is to convert the induced AC in conductors into a DC output. Before applying the DC current to the motor's coils, commutation is utilised in DC motors to switch the direction of the current.

Commutator Diagram

In This Diagram, Brushes are Connected with the Commutator

In This Diagram, Brushes are Connected with the Commutator

Working of Commutator

A commutator is a split rotary ring, usually made of copper, with one segment attached to each end of the armature coil. A commutator supporting each end of each coil on the multiple-coil armature must have the same number of segments. To provide the commutator segments and the accompanying armature coils with voltage, spring-loaded brushes are placed on each side of the commutator and make contact with it when the commutator rotates.

A constant rotating force known as torque is created by switching the direction of the current flowing through the revolving windings every half turn. With each half turn, the commutator in a generator reverses the direction of the current it picks up from the windings, acting as a mechanical rectifier to change the AC from the windings to unidirectional DC in the circuit.

Types of Commutation

When the current reversal is finished by the end of the commutation time, the calculation is known as an ideal commutation. If the current reversal is finished during the commutation time, sparking at the brush contact and overheating that damages the commutator surface take place.

There are three types of commutation methods to avoid defects.

  • Resistance Commutation

  • EMF Commutation

  • Compensating Winding

Interesting Facts

The armature of power tools, home appliances, starting motors, windscreen wipers, and the automobile sector all use commutators.

The commutator's segments are composed of copper and are spaced apart by mica insulation. The mica is shaped to sit beneath the copper strands. To make soldering the coil ends easier, slots are carved into the riser of the commutator.

Solved Questions

1. Why is the commutator made up of copper?

Solution: In brushed commutators, the brushes are typically constructed of either copper or. Carbon brushes have more uniform wear, produce less sparking, and harm the conductive metal segments less. However, copper brushes work better with high currents and extremely low voltage.

2. What would happen if the commutator was not there?

Solution: The magnetic fields of the rotor and stator would collide in the absence of a split ring commutator, preventing the current from reversing when the armature is reversed. As a result, the rotor would become stuck and cease to rotate.


A popular switch used in electronic products is the commutator. A torque, or constant rotating force, is created when the direction of the current flow changes every half revolution of the winding. The way the shaft, commutator, and armature are wound r determines how well the commutator functions. Although the voltage produced in the commutator might be zero to maximum, the polarity always remains fixed. A commutator has two main purposes: it maintains constant armature torque and MMF and transforms alternating current into direct current, serving as a rectifier in the process.

Competitive Exams after 12th Science

FAQs on Commutator

1. Why does a commutator spin?

A magnetic field is created when current enters the armature coil, and it tends to line up with the external permanent magnetic field which is set up by the permanent magnets. The coil thus turns. Additionally, this causes the commutator to rotate, because the commutator is attached to it and each time it does, the carbon "brushes" up against the copper. As a result, we get the commutator spin in the device like a motor which we use in our daily life.

2. Why is the commutator not used in an AC generator?

However, in the case of alternators, a commutator is not necessary as the output will only be AC (Alternating current) and not DC (Direct current). The sole function of a commutator is to convert AC to DC or vice versa. Since the generation in the case of DC generators is AC, the AC will be converted to DC using a commutator. So, we don’t use commutators in AC generators, it is only used in DC machines like DC motors or DC generators.

3. Why are split rings called commutators?

After each half-rotation of the coil in the device the split ring, these have a ring-like structure that is divided into two parts sometimes referred to as a commutator, in which an electric motor reverses the direction of the current flowing through the coil. This gives us the result that the coil keeps rotating in the same direction. The purpose of a split ring is the same as a commutator so to make it easy to understand, we call them split rings.