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Pros and Cons of Slip Ring Induction Motors

May. 18, 2022

An alternator is a generator that converts mechanical energy into electrical energy in the form of alternating current. An alternator in an electrical apparatus consists of many parts. and this article will describe some facts of the slip rings motors.

Slip Rings Usage

Slip rings can play a variety of roles in a motor. The primary function of slip rings is to transfer energy within the moving and stationary parts of the alternator. However, slip rings can play other important roles in an alternator. Typically, you can determine what role the slip ring will play by the size and current type of slip ring.

In addition to energy distribution, slip rings can be used for many other purposes. For example, you can find slip rings in both DC and AC alternators. Therefore, the function of slip rings in AC, DC and automotive alternators may be slightly different.

Slip rings are used to distribute the magnetic field from the shaft. The shaft in an alternator provides the conductive material, such as the magnetic field. The slip ring is connected to the rotating assembly. In such a way that the current in the alternator is distributed evenly. As the coil provides the current required for the rotor and magnetic field, the slip ring converts it to the required current.

Slip rings are essential even when the alternator has both DC and AC current. When the alternator is DC, the slip ring helps to reverse the polarity and thus helps to output DC to the correct section. In generators, slip rings assume the AC output. However, in an automotive alternator, the slip ring will only provide the DC voltage needed to keep the rotating system moving.

Purpose of Using Slip Rings in Induction Motors

Low Voltage Slip Ring Induction Motor

The construction of a slip ring induction motor is identical to a squirrel cage motor. We make use of rotor bars in squirrel-cage motor, but in-ring type makes use of windings that are connected in star. High resistance is then connected to these rings in series, which then act as an outer circuit.

Pros of Slip Ring Induction Motor

A good level of starting torque to support loads with high inertia.

It has a low starting current due to the effect of the external resistance.

It can take a total load current that is about 6 - 7 times higher

There is the possibility of adding more resistance to regulate the speed.

Cons of Slip Ring Induction Motor

Sophisticated construction

Higher cost of maintenance due to slip rings and brushes compared to other motors.

High rate of copper loss

Low efficiency and low power factor

More costly than 3-phase squirrel cage induction motor

Purpose of Using Slip Rings in Induction Motors

High Voltage Slip Ring Induction Motor

Slip Ring Induction Motors Usage

They are used to start the torque of a motor when a high current is needed. When you reduce inductive reactance, there will be a reduction in the phase difference between the EMF induced And with this, a sufficient unidirectional torque that can develop high starting torque is generated.

It is used for regulating the speed of a rotor or device. And this is due to the other end of the slip ring linked to the variable resistor.


The slip ring is an integral part of the alternator. You can find it in both DC and AC alternators.

In a DC alternator, the slip ring reverses the polarity and helps discharge the DC output. Meanwhile, in an alternator, the slip ring discharges the AC output in the generator or appliance. For automotive alternators, slip rings can excite the rotor with a low DC voltage.

Please contact ZCL if you need, we have various kinds of motors for sale.

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