Types of Motor Starters Explained: Features & Uses

Is your motor's lifespan reduced due to frequent inrush currents? Or do you often have overheating problems with your appliances? Then, a motor starter might be the solution. Motor starters are specially designed devices that protect your motors from overloading and overheating while also allowing you to have a hazard-free workspace. 

However, motor starters come in many different types and sizes. Choosing the right types of motor starters might often come off as too complex and tough. Hence, read this article to get insight into the motor starters and their types, which are explained in comprehensible terms. 

What are Motor Starters?

Motor starters are simple electric devices used to safely start and stop electric motors. They must be installed to ensure that the motors are started without too much inrush current, which can possibly damage the device. 

When the electric motors are turned on, they usually pull a lot of power together, which can lead to an overload. With motor starters, the current flow slowly increases as needed without damaging the device. Motor starters are also used to control voltage spikes and the problem of overheating. 

Why are Motor Starters Necessary?

Electrical equipment like motors often has rough startups owing to the huge current inrush that takes place as it is turned on and the difficulty of not having enough torque to commence the movement. Hence, the invention of motor starters has been beneficial. Here are some other benefits of having motor starters: 

1. Protect Motors From Overload

When motors are started, the initial inrush current is usually high because of the huge current requirement. This can potentially damage the various appliances in which the motor is installed. Hence, a motor ensures that the overload is controlled and the voltage slowly rises to the required amount after being turned on. This is also useful while turning off the motor. 

2. Ensure Smooth Operation and Longevity

Motor starters can automatically detect an imbalance in the current and disconnect if the voltage is too high. In fact, they also create a similar level of current flow to the motor, maintaining smooth operation and ensuring good long-run performance. This also promises a smoother start and low load shocks on the system. 

3. Provides Low Voltage Management

Another important feature of a motor starter is the management of low voltage. This efficient management is essential since low voltage levels can be too inadequate for the device, causing mechanical failure and longevity issues. In such a case, a motor starter immediately disconnects the supply upon sensing the voltage going below a certain level. 

4. Improves Safety 

Since the motor starters help in managing high voltage and low voltage situations, they also, in return, ensure the safety of the equipment and the user. In addition to that, optimal usage of the motor starter also lessens the chances of electrical hazards. Mechanical failure is also checked upon with a motor starter, which can provide safer and better working conditions in the electrical industry. 

5. Enhances Energy Efficiency 

In most electrical appliances, energy efficiency matters a lot, especially when consumption is supposed to be higher than normal levels. With a motor starter, energy is consumed at moderate rates, maintaining a balance between the probable fluctuations that may arise in the voltage. It also promises a smooth start and stop option that reduces overload issues.  

Types of Motor Starters

There are many types of motor starters in use today. Some of the major types of motor starters that are used often include the following: 

1. Manual Starter

As the name suggests, this is operated through a switch that is turned on and off manually. It has zero automated systems integrated into it, which makes it a simple circuit-making and breaking switch. These types of motor starters are often employed in places that do not require much voltage maintenance, such as low-power motors. That being said, they also lack protection for low voltage fluctuation, which can prove to be risky. 

2. Magnetic Starter

A magnetic starter is one of the most widely used types of motor starters. It usually employs electromagnetism to make and break circuits. Today, these magnetic starters are readily found in high-power AC motors. In addition to providing the basic current balance, it is also beneficial to manage low-current and high-voltage scenarios. Besides, a magnetic starter usually has two types of circuits, one being the power circuit while the other is a control circuit. 

3. Direct Online (DOL) Starter

The Direct Online Starter is the simplest motor starter among all the types used today. This type of starter is directly connected to the power applied and maintains protection against overloading or high current inrush. The starter is turned on and off using a simple switch that connects the circuit when turned on and breaks it when off. This design is often found to be very budget-friendly and provides high starting torque for a smooth initiation. 

4. Stator Resistance starter

The Stator Resistance starter is a unique motor starter design that utilises a reduced voltage starter system. This mechanism is essentially made up of a series in which external resistance is added to each phase. This resistor ensures that the initial voltage remains under control. As the motor is turned on, the resistance remains high and then drops as the voltage is stabilized. This type of starter, thus, provides smooth functioning. 

5. Rotor Resistance or Slip Ring Motor Starter

The rotor resistance motor starter is specifically used on a slip-ring induction motor, which gives rise to its other name. This simple mechanism is built with external resistances that remain connected to the rotor in the device, which ensures that the rotor current is under check. The external resistors only come into play while starting the motor, which attempts to manage the inrush current. This is one of the best motor starters, providing a broad range of speed control.  

6. Autotransformer Starter

Autotransformer motors aim mainly to reduce the current inrush. This motor starter is connected to star and delta motors, providing better torque during initiation. This is beneficial for large motors in industries and factories that are often exposed to a massive amount of current load. Moreover, the autotransformer starter, though large in size and more pricey than most, provides a flexible mechanism that can be widely employed without much electrical risk. 

7. Star Delta Starter

The star delta starter is one of the most commonly used types of motor starters for large motors. This type of starter usually follows a mechanism wherein, as the motor's speed accelerates, it lets the timer relay switch the star connection into a delta connection, permitting maximum current passage. The star delta starter is designed minimalistically and thus does not cost much. It even does not have many maintenance requirements and can support large motors with long acceleration times. 

8. Soft Starter

The soft starter is one of the few types of motor starters that utilize the TRIAC switch. The TRIAC is basically a semiconductor switch that can control the voltage load and limit the initial current overload as well. In fact, the voltage is allowed to increase slowly after the starting as the current stabilizes. Due to this, the operation remains smooth with no jerks or voltage ups and downs. This also promises extended longevity for the system.  

9. Variable Frequency Drive (VFD)

The variable frequency drive, like the soft starter, is also used to carry variable voltage across the system. It specializes in maintaining the supply of the voltage in the induction motors, which can increase or decrease their speed. One of the top benefits of using this out of all the other types of motor starters is its provision of smooth acceleration for larger motors with a speed control available alongside. This also limits the mechanical stress induced. 

How to Choose the Right Starter?

Choosing the right motor starter among all the varying types is no easy job. While some may have a better initial inrush current balance, others might prove to be more useful for seize-specific motors. Hence, having an idea about the factors that influence the choice of motor starters is essential. Listed below are the most common aspects to consider before purchasing one:

1. Cost and Size

These aspects are essential to consider when picking any type of motor starter in the market. Usually, the larger motor starters cost more but offer a variety of options, while the smaller ones can generally be cheaper. However, some motors may require bigger starters than others. 

2. Maximum Torque

Also known as full torque at zero speed, this is the motor's capability to generate maximum torque output when it is operational or non-moving. The frequency setting of the motor often determines whether there will be high torque production or not. 

3. AC Coil Control Power

The AC coil control power refers to the power needed to power up the contactor's coil, which can, in turn, energize the motor. It should be enough to at least energize the motor and close the contacts without fault. 

4. Overload Relay Range

The overload relay is a device that prevents motor overloading and overheating. This range is the range of current values needed to initiate the relay for the protection of the motor. Hence, it is important to pick the right range that matches the full load current of the motor. 

5. Contactor Size & Line Power

In order to handle the motor's line power, the contactor size should be properly chosen. To make a good choice, the type and application of the motor and the voltage requirements must be considered. 

6. Cover Buttons

The cover buttons, or the pilot lights and switches located on the outside of the control panel, are also important factors. It is essential to install switches that are within reach, display the right information, and are safe from electrical hazards.  

Applications of Different Motor Starters

Motor starters are used for a variety of reasons across different industries. Some may only do the job of reducing the initial current overload, while others may come to benefit the users in many other ways. Therefore, here are the applications of different motor starters: 

1. Soft Starters

These types of motor starters are supposed to be used in large motors where voltage control and balance are important. Many heavy motorized systems and centrifugal pumps commonly use these in industries. 

2. Autotransformer Starters

Autotransformer starters are some of the most convenient motor starters. They allow effective inrush current management, smoothing the system's function. These are used across mill motors and even compressors. 

3. Star Delta Starters

Designed for medium-sized motors, Star Delta starters effectively manage the initial current overload. They are also cost-effective and are, hence, commonly used for fans and pumps. 

4. Variable Frequency Drives

Known as some of the best types of motor starters, these provide speed control in motor speed and aim for optimal energy usage. Due to this, these are widely used as industrial tools. 

5. Direct Online Starters

Also termed DOL starters, these are often used in small and medium-sized motors that do not have many inrush current management requirements. They are also simpler to build than other mechanisms in use today. 

6. Manual Starters

These are suitable for low-voltage protection settings and should be employed in places where the motor power required is low. They could be used by small fans and light-duty machinery. 

Motor starters have proven time and again to be one of the electrical industry's widely accepted achievements. From offering optimal energy conservation with no compromise in speed and efficiency to reducing electrical hazards in the motor, different types of motor starters keep the current in check and offer device longevity. 

So, if you want a suitable motor starter for your factory or personal usage, consult NoBroker electrical services. They can assist you in choosing the right one and even help you with the installation of the motor starters.

Frequently Asked Questions