An electrical device known as a motor starter is utilized to start and stop a motor in a risk-free manner. In the same way that a relay turns the power on and off, a motor starter does the same thing, but unlike a relay, it also protects against low voltage and overloading. The most important functions of a motor starter are to start a motor safely, to stop a motor safely, to reverse the direction of a motor, and to protect the motor from low voltage and overloading. Other functions include reversing the direction of a motor. Starters are pieces of equipment that regulate the flow of electrical power to various pieces of machinery.
Starters are what really “start” motors, as their name suggests. They also have the ability to halt, reverse, speed up, and defend themselves. Contactors and overloads are the two components that are used in the construction of starters. Contactors are responsible for regulating the flow of electric current to the motor. Their purpose is to continually complete and break a circuit carrying electrical electricity. Overloads, on the other hand, prevent motors from drawing an excessive amount of current and “burning out” as a result of excessive heating. This page will help you better understand the different types of motor starters like a heavy-duty, starter motor, single-phase motor starter, medium voltage motor starter, electrical motor starters, and the like.
What is a motor Starter?
Prevention and protection play a significant role in maintaining a high level of operational efficiency in an industrial or commercial enterprise. In order to achieve this goal, numerous different devices are used in order to improve functionality while also protecting against the typical challenges and problems that are associated with operation. Motor Starters are available in a variety of ratings and sizes, which correspond to the ratings and sizes of the corresponding alternating current (AC) motors.
These starters not only provide the required power to the motor in a secure manner but also stop the motor from drawing excessive currents. Let’s have a look at some further information on the need for a motor starter, the many kinds of motor starters, and the wiring schematics for each of them. Because AC motor starters are the workhorses of industrial and commercial applications, it is the only kind of motor starting that we are going to tackle in this article.
Why Do We Require a Starter that also Includes a Motor?
The use of a motor starter is required in order to get an induction motor going. This is due to the low rotor impedance that it has. The slips of your induction motors, which are the relative speeds between the rotor and the stator, are ones of the biggest factors that determine the rotor impedance. The slip causes an inverse relationship between the impedance and its value.
Because the induction motor’s slip is at its greatest, or 1 while it is in the rest position, the impedance is at its lowest, and the motor draws what is known as an “inrush current,” which is an extremely high quantity of current. Because of the large inrush current, the air gap between the rotor and the stator becomes magnetized, which causes an EMF to be induced in the rotor winding. This electromagnetic field (EMF) causes an electrical current to flow in the rotor winding, which in turn generates a magnetic field and torque in the rotor. When the rotor speed is increased, the slip of the motor reduces, which results in a lower current being drawn by the motor.
How Does the Starter Work on a Motor?
A control device known as a starter may manually or automatically turn the motor on or off, depending on the user’s preferences. By creating or breaking its connections, it may provide a safe method of controlling the ON and OFF states of electrical motors.
- The hand-operated lever on the manual starting is moved manually to the ON or OFF position in order to manually move the contacts. The manual starter is utilized for motors that are not very powerful. The fact that these sorts of starters have to be switched ON after the power frailer is another drawback to using them. To put it another way, they need human control for each function (ON or OFF). This procedure may sometimes cause strong currents to flow through the windings of the motor, which can result in the motor being damaged or even destroyed. Because of this, it is not advised in the majority of situations where other possible motor starters with protection, such as automated starters, are utilized instead.
- On the other hand, the ON/OFF functionality of the motor is controlled by automatic starters. These starters are composed of electromechanical relays and contactors and are used to turn the motor on and off. When electric current flows through the contactor coils, it energizes the coils and creates an electromagnetic field. This field either pulls or pushes the contacts, so establishing a connection between the motor windings and the power supply.
Several Methods That Can Be Employed When Building Motor Starters
In comparison to any other kind of motor, the vast majority of industrial operations make use of three-phase induction-type motors. When it comes to starting a three-phase induction motor, there are a few various approaches that may be used. Let’s first talk about the methods that are utilized for induction motor starters before moving on to the many kinds of starters that are available.
-
Full Voltage Technique
Direct on-line starting, or DOL starting as it’s more often known, is by far the most frequent technique for getting a three-phase induction motor up and running. Because the motor is intrinsically capable of starting itself, this method involves applying the whole voltage, also known as the rated voltage, across the motor. This is because the motor needs the full voltage in order to start.
- As was said before, you may only use this method on motors with horsepower ratings of five horsepower or fewer. Starters for motors that use this technology are referred to as DOL starters. Reduced voltage technique: This approach is used for big motors with horsepower ratings of 100 and above (or for a motor that takes very high starting currents). As was previously mentioned, high-rated motors have a tendency to draw very large beginning currents and are also capable of causing a voltage drop in the line.
- In these kinds of situations, a technique called “reduced voltage” is used, in which the voltage supplied to the motor is initially lowered for a few seconds, long enough for the motor to begin rotating, and then the voltage supplied to the motor is raised to its rated supply voltage, causing the motor to rotate at its rated speed. Starters for motors that utilize the strategy of lowering the voltage are referred to as reduced voltage starters. The stator resistance starting, the autotransformer starter, and the start-delta starter are examples of decreased voltage starters that are used often.
-
Bidirectional Starter Technique
For some procedures, it is essential to run the motor in both the forward and the backward directions simultaneously. Altering the order of the RYB wires on a three-phase supply is the typical method for reversing the direction of a three-phase motor. This may be done by switching any two of the supply’s wires. In order to accomplish bidirectional functioning using this technology, two contactors are used, each of which is equipped with an appropriate connection and interlocking mechanism between the two of them.
-
Multi-speed Technique
In this technique, the motor starters are constructed in such a way that they can provide the motor with a variety of voltages, allowing the motor to run at a variety of speeds. In most cases, these starters are constructed to allow the motor to be operated at two or three distinct speeds by using two or more contractors. The vast majority of these starters come in both full-voltage and lower-voltage variants.
Circuits in a Motor Starter
Below are the different circuits found in a motor starter:
-
Power Circuit
The power circuit establishes a connection between the line and the motor. It facilitates the flow of power to the motor by way of the starting contacts, the overload relay, and finally to, the motor itself. The power connections, also known as the main contacts, of the contactor are what carry the motor current.
-
Control Circuit
It is responsible for operating the contactor and turning the motor on and off. The major contacts of the contactor are the ones that are in charge of allowing electricity to flow to the motor. In order to do this, the contacts that are part of the control circuit are either opened or closed. The contactor coil is given a charge by the control circuit, which results in the formation of an electromagnetic field.
To sum it up…
A motor starter offers protection by initially regulating the electrical output of your gadget or equipment at the very beginning of its operation, when you switch it on or when it engages. This is the time at which it is most vulnerable to potential damage. After that point, the starter will continue to act as a fail-safe and guard your system from any threats. You may visit https://www.se.com/th/en/ if you want to learn more about motor starters.
