What is a Motor Starter and How Does a Motor Starter Work?

Electric motors are considered crucial equipment in industries and commercial facilities in the management of machines and equipment. Still, starting these motors is not as easy as turning on an on/off button, or a switch for that matter. Its operation needs to be professionally managed to avoid any damage since it can be dangerous to handle. This is where motor starters are helpful. It is essential for anyone who is responsible for managing or maintaining specific motor-driven equipment to understand what is a motor starter, all types and how it works.

What is a Motor Starter?

A motor starter is a special type of electrical equipment that is widely used for starting, regulating, and protecting electric motors. Its main function is used in the regulation of the inrush current at the start of a motor is both very destructive and momentary, and acts as a protector against overloading and short circuits. Motor starters help control motors, and they are used in any electricity-using system, be it a small domestic appliance or a massive industrial machinery. The motor starter function does not only include the starting of the motor. It also involves halting the motor.   

How Do Starter Motors Work?

You must know what inrush current is before proceeding to the operational mechanism of starter motors. Electrical motors, when initially supplied with electricity, usually consume a fairly large current, that is, inrush current, which may actually be several times larger than the normal current. Such a sudden rush of current poses a real threat to the motor's winding, and in extreme situations, it can cause the circuit breaker to trip or a fuse to blow.

A motor starter eliminates this problem. The purpose of motor starter involves applying power to the motor gradually in a way that the motor will get to its full speed gradually. The control circuit of the motor starter generally consists of contactors, overload relays, and, in certain networks, resistors or VFDs for managing the inrush current and electrical phase faults in the motor.

Also Read: Complete Guide About Motor Driver

Types of Motor Starters

Motor starters can be categorised into various types depending on their application and the size of the motor they are going to control. It is essential to be familiar with the various types of motor starters as a way of arriving at the most suitable one.

• Manual Motor Starter: A manual motor starter is a very basic switch that is used to start and stop a motor. Often, it has a switch/lever which, when pressed, completes or interrupts the circuit, thereby making or breaking the flow of electricity to the motor. Contactors are used in small, low-power motors where automatic control is not required. The main strength of a manual motor starter is that they are inexpensive and relatively easy to implement. However, it lacks the extent of safety and command as the other types of starters so it is not appropriate for the larger motors or complicated operations.
• Magnetic Motor Starter: A magnetic motor starter control the operation of the motor by using an electromagnetic coil. When the coil is energised, the contacts get closed and hence the electricity gets supplied to the motor. The stator coil is de-energized; therefore, the contacts in the circuit break, switching off the supply to the motor. Magnetic motor starter is often used in applications where the motor must be controlled from a distance or turned on/off automatically. They also provide other enhanced protection characteristics, for instance, overload protection and short circuit protection. Moreover, they can be interfaced with other controllers like the PLC for supervisory control of more elaborate varieties of motor management.
• Direct-On-Line (DOL) Starter: The Direct-On-Line (DOL) starter is among the simplest types of motor starters as well as among the most popular. It links the motor directly to the voltage supply. It enables the motor to start operating with full voltage. This type of starter suits small motors in cases where it is not important to limit the amount of current that rushes through the motor. The main benefit of a DOL starter is that its construction is simple and nearly exempt from malfunctions. But it does not decrease the inrush current so it is not suitable for the larger motors for which the starting current can potentially harm the motor and trigger the circuit breaker.
• Star-Delta Starter: The Star-Delta starter is a more advanced type of motor starter widely used in industries to decrease the inrush current during starting. It initially connects the motor in a star; this means that the voltage across each winding is reduced, thus reducing the current that starts the motor. Once the motor reaches a certain RPM, the starter shifts from the utilisation of y-connections to d-connections which gives full voltage to the motor. The Star-Delta starter is usually applied in the areas where the motor must begin with a minimum amount of current to avoid damage or to decrease electrical stress. They are mostly used in applications where the initial inrush current is likely to be high especially when applicable to large motors.
• Soft Starter: A soft starter is more of an electronic device that steps up the voltage supplied to the motor in a gradual manner, and this is contrary to the high inrush current of other types of starters. Soft starters are mostly utilised where factors like acceleration and deceleration are important in working systems such as conveyors, pumps, and fans. The main benefit that can be obtained from utilising a soft starter is that it lowers mechanical stress on the motor and the driven equipment, and thus increases their service life. Furthermore, soft starters can be told to give a variety of initial torque and accelerating ramps to give them an almost completely universal utility.
• Variable Frequency Drive (VFD): A Variable Frequency Drive or a VFD is more powerful than a motor starter as it not only adjusts the starting current but also the speed and the torque of the motor also. A VFD works by modulating the frequency of the power supply, and this makes precise control of the motor’s speed suitable for installation in processes that require good speed control.

Also Read: DOL Starters for Agricultural Motors and Pump Sets

Summing Up

A motor starter is an essential device that safely manages the starting and stopping of an electric motor, protecting it from electrical faults and ensuring smooth operation. By controlling the initial inrush of current, motor starters extend the lifespan of motors and enhance their performance. Understanding how motor starters work helps in selecting the right one for your specific application, ensuring safety and efficiency.

For those looking to purchase high-quality motor starters, the eShop of Lauritz Knudsen Electrical and Automation offers a wide range of options. With a user-friendly interface and top-notch customer support, it’s the best place to conveniently buy motor starters that meet your needs.