Slip Ring vs Commutator

by | Jun 28, 2021

If you are the greed hand in the slip ring field, I am sure you will be confused with the slip ring and commutator. They are similar in shape and both are used in alternator and motor, actually, there is a major difference between them.

In this post, you will learn this:

What is a slip ring?

The slip ring is called several names: rotating electrical connectors, electrical swivels, or an electrical rotary joint. It mainly uses any electromechanical device that requires unrestrained, intermittent, or continuous rotation while transmitting power and data.

Slip ring is an electromechanical device used to connect a stationary system to a rotating system. You will find a slip ring in application programs that needs consistent rotation while transmitting electric power or signals. It performs the task of improving the mechanical performance in electric machines.

How does slip ring work?

Slip Ring structure

There are two main components in the slip rings; the metal ring and brush contact. The total number of rings and brushes is determined by the application and the design of the machine.

The metal rings consist of conductive metals like brass and silver. The rings are separated from each other by nylon or plastic to reduce friction between them during operation.

On the other hand, the brushes consist of graphite or phosphor bronze. If you are considering costs, the graphite option is preferable. But for longevity and high conductivity, phosphor bronze is the best option.

The placement of the brushes or rings depends on the rotation per minute.
The brushes are either fixed with rotating rings or the rings are rotating with fixed brushes. Regardless of the arrangement, the brushes maintain contact with the ring by pressure from the springs.

Most of the rings are placed on the rotor, and it rotates consistently while the brushes are attached to the brush house and are static. The slip rings work by ensuring that electrical current is transmitted through the brushes as the rings rotate. Thus, making a continuous connection between the rings and the brushes.

What is the purpose of the slip rings?

Slip rings are used in many industries, including construction, agriculture, aerospace, medical/pharmaceutical, and packaging industries.

The purpose of the slip rings in an electromechanical system is to increase their mechanical performance. It also helps break down the simple operation process into smaller bits. The slip rings are also used to neatly arrange wires hanging around the movable joints of the machine. This is to prevent them from interfering with rotating operations.

Types of slip rings

There are different types of slip rings. Each serves specific purposes in an electromechanical system. They have unique features that make them able to perform various functions. They are:

1. Capsule slip rings: These types of slip rings are used where there is limited space.

2. Modular slip rings: These slip rings are used to slow down the speed of the machine. They are used to transmit up to 30 amps.

3. Fabricated slip rings: They serve the purpose of rebuilding, repairing, and re-insulating carbon brushes and damaged slip ring units.

4. Barrel slip rings: Just like the modular slip rings, the barrel slip rings are used in machines where you require a much slower and medium speed.

5. Pancake slip rings: Just like pancakes, these types of slip rings are flat-shaped. They are used to transmit power and signals in areas where height is a challenge and is restricted.

Where does slip rings use in machines?

Wind Turbines

Wind Turbines:  slip rings are used to stop the cables from twisting as current flows through the pylon of the wind turbine.

Moving Head Projectors: They are also called moving lights. They are used in film theatres and TV shows. They are made with several motors that make it easy to move them when quiet, smooth, and fast movements are required. The slip rings serve the purpose of helping the projectors move and turn in different directions at the same time. It also protects the cable in the moving head projector from damage.

Other machines where the slip ring is used includes:

Automatic machines

Medical systems

Bottle labeling machines

Robots

CCTV systems

Packaging

Video systems

Advantages of using slip rings

Some of the advantages of using slip rings in your electromechanical application:

1. It increases the lifespan of the machine.
2. It is reliable.
3. It is economical and cost-efficient.
4. Slip rings in your machines make themThe slip able to function in extreme environments.
5. Improves the quality of your machine.

What is a split ring commutator?

commutator

A split ring commutator is a rotating electrical switch in electric motors and generators that changes the current direction in the rotor and external circuit.

A split ring commutator is made of copper, and individual segments of the ring are joined to each end of the armature coil.

The number of segments in the split ring commutator is determined by the number of coils in the armature. If the armature has multiple coils, the split ring commutator will also have multiple segments.

How does commutator work?

It comprises a cylinder made of several metal contact segments fixed to the rotating shaft and attached to the armature windings. There are brushes loaded with springs seated on each side of the split ring commutator that touches the commutator as it turns. When this happens, it releases electric current to the commutator segments and the armature coils with voltage.

When the brushes glide on the gap in the split ring commutator, the electric charge changes the segments of the commutator and the electrical polarity of the armature coils. This is done to ensure that the rotation of the armature is maintained in one direction.

Occasionally, the amplitude of the voltage between the brushes alternates between zero and a pre-set maximum value. But it always maintains a constant polarity.
The split ring commutator changes the transmission of electric current in a winding as the shaft rotates.

In a single armature winding, as soon as the shaft makes one-half complete turn, the winding connects so that current passes through it in the reverse direction.
In a motor, the armature makes the fixed magnetic field apply a force in a circular direction on the winding to make it turn.

When used in a generator, the mechanical torque applied on the machine’s shaft maintains the speed of the armature winding through the static magnetic field. Thus, creating an electric current in the winding.

The split ring commutator in a motor and generator alters the direction of the current flow through the winding.

What does a slip ring commutator do?

It is also known as a commutator. The slip rings of the commutator consist of phosphorus bronze. The slip ring commutator is a device attached to the armature core, and it transfers the current from the armature winding.

Depending on the requirements of the machine, the slip ring commutator can switch the AC to DC or change it from DC to AC.

The slip ring commutators are made up of divided segments known as commutator segments. These divided segments are arranged in a series, and the armature winding extensions are connected to it. These segments are made of hard-drawn copper of high conductivity, and each of these segments is made of dual coil sides.

The total number of the segments is equal to the number of coils. The coils are attached to the brush that receives current from the segments.

The slip ring commutator performs the dual function of a rectifier or an inverter. That is, it can convert AC to DC or a DC to AC. It is used in DC generators and motors, AC generators and engines, and universal motors.

The difference between Slip ring and commutator

The slip ring and the commutator are used to keep up the connection between the rotating and electrical systems. Both are made up of materials that allow them to conduct electricity. But functionally, they are different.

Differences between the slip ring and the commutator

There are some visible differences between the slip ring and the commutator. Here are the differences at a glance:

Function

The slip ring connects a rotating and stationary system without altering the polarity of the machine.

The commutator connects the rotating system and the stationary system but changes the machine’s polarity in a reverse direction.

Uses

The slip ring is used in AC motors to provide a constant flow of electric power.

The commutator is used in DC motors to reverse the polarity of the current in the armature AC and the armature winding extensions.

Design

The slip ring is an endless ring of conductive metal materials.

The commutator is a ring split into two or more parts.

How to choose slip ring or commutator in the machine?

The commutator and slip ring are used to maintain the continuity of the circuit between the stationary and rotating parts. The most crucial difference between them is that the commutator can convert AC to DC (or DC to AC), whereas the slip ring can not.

The commutator converts direct current into alternating current. The DC motor runs on direct current, but it is essentially AC if you check the voltage or current waveform of a particular winding. The following diagram correctly illustrates the action of the commutator. In the DC motor, the commutator acts as an inverter (converting DC to AC). In a generator, it acts as a rectifier (converting alternating current into direct current).

Compared with the commutator, the slip ring has only one function, enabling the connection between the fixed system and the rotating system. For example, to power, the rotor of an induction motor, consider using a slip ring.

Summary

Both slip ring and commutator are widely used in industrial, they have similar function and also have different. 

You should know the detailed request of your project before choose the slip ring or commutator.