Induction Motor Protection System Circuit and Its Working

The electric motor is the most crucial drive in the modern era of automation. These motors are used in various industrial applications. But these motors can be protected from the different mechanical and electrical faults for helping their purposes. This article discusses a protection system for induction motor from emerging faults using embedded microcontrollers. The induction motor experiences various kinds of electrical faults such as overvoltage or under voltage, unbalanced voltage, overload, earth fault, phase reversing and single phasing. Due to these faults, the windings in the motor get heated which leads to reducing the life of the motor. The faults in the motor may occur due to faults in the motor or the driven plant, conditions executed by the external power supply n/w. The degree of the induction motor depends on the applications and costs of the motor.

What is an Induction Motor?

An induction motor or asynchronous motor is the most commonly used motor in various applications. Because these motors always run at a slower speed than synchronous speed. Synchronous speed can be defined as, the speed of the magnetic field which is rotating in the stator. Induction motors are classified into two types based on the sort of input supply such as single-phase induction motor and three-phase induction motors. Induction motors are classified into four types namely; split-phase induction motor, capacitor start induction motor, capacitor start capacitor run induction motor and shaded pole induction motor. And also based on the type of rotor three-phase induction motors are classified into two types such as wound type, slip ring motor squirrel cage motor.

Working Principle

In a DC motor, supply is required to be given for the rotor winding as well as the stator winding. But in this motor, only an AC supply is fed with the stator winding.

Alternating flux is formed around the stator winding because of the AC supply. This flux rotates with the synchronous speed that is called as RMF (Rotating Magnetic Field). An induced emf can be caused by the comparative speeds between rotor conductors and stator RMF. According to Faraday’s electromagnetic induction law, the rotor conductors are short-circuited, and later the rotor current is generated because of an induced emf. That’s why these motors are called as induction motors.

Now, the current which is induced in the rotor will also create an alternating flux around it. According to Lenz’s law, the direction of the induced rotor current is, it will tend to oppose the cause of its production.

Induction Motor Protection System Circuit and It’s Working

The main goal of this project is to design an induction motor protection system for guarding the motors against any faults happening from single phasing and over-voltage conditions.

The induction motor is an essential device in various industrial applications. These motors work on 3-phase supply and a standard temperature to keep the loads at preferred conditions. But; if any phase goes lost or there is a growth in the temperature of the windings it harms the motor. Thus, the proposed system helps to give protection to the motors in the industries by eliminating the power to the electric motor immediately if any of the phases misses out of the 3-phases, or if the motor’s temperature exceeds the threshold value.

The proposed system uses a 3-phase power supply, where 3 single-phase transformers are allied to it. The project has a set of the operational amplifier which is used as comparators for relating input voltages. A thermistor is used to sense the temperature of the induction motor by connecting with the body of the induction motor. This motor is functioned by switching the main relay, which is worked by another set of relays by detecting single phasing & over-temperature conditions.

In the future, this project can be developed by using current sensors and a phase-sequence sensor for protecting the overloads and also the motor from applying the wrong phase sequence.

Induction motor Protection system from single phasing, over-voltage, under-voltage, overheating and phase reversal provides the smooth running of the induction motor expands its lifetime and also efficiency. Generally, these faults occur when the supply system is violating its rating. When the motor is running at rated current, load and voltage then these faults will not be generated. Generally, the smooth running of the motor can depend on the supply voltage under the set limit & load which is determined by the motor should also be under the stated limit.

Therefore, this is all about the induction motor protection system project and its working. We hope that the information which is provided in this article is very useful for you for a better understanding of this concept. Furthermore, any help in implementing electrical and electronic projects or others, you can approach us by commenting below.

Photo Credits:

• Induction Motor digikey
• Induction Motor Working Priciple explainthatstuff