It can cause several problems when the DC motor is not started correctly. The DC motor can crank and affect the torque that the motor generates. So you need to use good methods to start the motor. If you need to learn about the methods, this article will guide you to learn about them.
So, how to start a DC motor? You can start the DC motor by using various methods like 2-point starter, 3-point starter, 4-point starter, Thyristor starter, Manual starter, etc.
In this article, I will write about the starting methods of a DC motor, different types of starters, parts names, the necessity of a starter in a DC motor, and much more. Please read till the end to learn about it.
Starting Methods of A DC Motor
Knowing the best types of starting methods will help you in deciding the most convenient one. The starting methods are used to put external resistance in windings so that the current does not overflow. If the current overflows, then the wires of the DC motor will get damaged.
The basic DC motor starting equation is I = E/R. Additionally, the voltage equation of DC motor is Ia = (E – Eb) / Ra
The electrical circuits can handle a certain amount of current in the wiring. If it overloads, the wiring will get overheated. It can also lead to fire in the worst cases. So, you must control the current by using the starters. Please check out the below ways to learn the DC motor connection/starting methods of a DC motor:
2-Point Starter
The concept of the 2-point starter in a DC motor is to control the current by putting external resistance to the winding. In this method, the start arm is turned right. A certain amount of resistance is put in the series with armature. This process happens during the starting of the motor.
As the motor starts getting towards the clockwise position, the current starts getting reduced. If the motor gets speed, then the resistance will get decreased. Hence, it is necessary to control the motor speed as well. This method is also called a no-load-release coil.
This coil also releases the control arm from the run position when there is not sufficient voltage for the motor to function. The voltage may be insufficient due to poor wiring or bad contacts. However, here you may check out the 2-point starter diagram:
3-Point Starter
The three-point starter mostly works the same as the 2-point starter, In this method, this device puts resistance in the DC motor series with the circuit. As the circuit gets resistant, the current gets controlled. As a result, the DC motor can start without any problems.
The no-volt trip coil saves the DC motor from any potential damage when the voltage drops in. If the motor is running while there is no sufficient voltage for the DC motor to work, the control arm is turned towards the off position. Hence the power is cut. Consequently, the DC motor won’t face any damage.
However, there is also an overload protection coil except for the no voltage coil. It saves the DC motor from getting excessive current during the start.
3 Point Starter Drawbacks
You know how a 3-point starter helps to start the DC motor by now. But some drawbacks come into play during the start of the motor. Please check out below to learn about it:
- It is not compatible with variable-speed motors
- If you reduce the field current, the motor will get stopped
- This method is more complex than the other starting methods
4-Point Starter
A 4-point starter is quite similar to a 3-point starter. The 4-point starter uses four terminals to control the DC motor speed. The names of these terminals are the Armature terminal, the line terminal, and the field terminal. If it is a big DC motor, you should go for this starting method.
The 4-point starter is used for connecting the coil to the parallel line along with the resistor in the circuit. This way, the flow of current is controlled. This method comes in handy when the back emf is not able to control the overflow of current.
Because you can control the motor speed with the help of a 4-point starter. It does not solely help in starting the DC motor. However, you can check out the diagram of the 4-point starter below:
4 Point Starter Drawbacks
Similar to the 3-point starter, the 4-point starter also has its drawbacks. Comparatively, the 4-point starter may seem more helpful to you in starting the DC motor speed. However, please have a look through the below points to find out about it-
- It cannot limit the speed of the high current of the DC motor
- If the speed needs to be increased and field winding is opened, then the motor will get stopped. It is because the current turns to zero when the flux doesn’t work properly
Thyristor Starter
The Thyristor Starter is a machine that helps the DC motor to start smoothly and also controls the flow of current. The Thyristor starter acts as a switch that helps to control the voltage. This soft starter depends on the voltage to control the flow of current in the DC motor.
In addition, the Thyristor starter gradually increases the speed to its rated voltage so that the DC motor can function properly. It also helps to maintain torque perfectly. So the DC motor can stay safe from over-voltage and potential damage.
Here is the diagram of a Thyristor starter:
Different Types of Motor Starters
You have known about the best methods of starting DC motors. But there are some more types of starters in DC motors that you may want to learn about. So, please have a look here to know about it:
Magnetic Starter
A magnetic motor starter is an electronic device that helps a DC motor to start. It also protects the motor from any kind of damage and overload. In this starter method, the current is produced in the DC motor’s stator. It creates a magnetic field around the stator.
As the stator receives a magnetic field, it causes the rotor to move and rotate. This way, the DC motor is started. You can be worry-free if you use this method. The Magnetic starter makes the safest start in the DC motor.
Auto Transformer Starter
The Auto Transformer Starter plays a big part in reducing the voltage of the DC motor. This starter also takes low maintenance. It is not quite expensive like the other starting methods. In this method, the increased impedance gets increased which lowers the current. The Auto Transformer Starter method is better for the induction motor having a rate of more than 15 HP.
Reversing Starter
The Reversing Stator can work very well in starting the DC motor. It works through the electromagnetism. There are three motor supply lines in the Reversing Starter. When you lead two power lines to the motor line, it creates a magnetic field.
The magnetic field leads the rotor to move and the motor starts rotating. This way, the Reversing starter helps the DC motor to get started.
DoL Starter
The DoL Starter is used to start a three-phase induction motor. The three-phase lines of the DC motor and three-phase supply are connected. Then the full voltage is applied to the motor. So the motor gets started.
However, it is best to avoid using this as a starter method if there is a voltage drop issue. It can lead the DC motor to get damaged or lower its life expectancy.
Star-Delta Starter
The Star-Delta Starter method is also used in three-phase induction motors. In this method, the voltage of the current is reduced at the starting point. This method is mostly suitable for high-power rating motors. It can be used for extreme light loads as it can lower the voltage very well than the other ones.
DC Motor Parts Name
You may want to know about the basic parts of the DC motor to identify the components. Please have a look below as I have written about the DC motor’s parts in detail:
Stator
The Stator is a stationary element of a motor. It creates a magnetic field which causes the motor to rotate. That magnetic field leads to generating current in the DC motor. The stator restricts the high-power current in the DC motor. This stator is found in electric motors, generators, and biological rotors.
Poles
Poles are electromagnets. These electromagnets held the field windings. The pole gives magnetic flux to the DC motor. However, the poles cannot generate magnetic flux if the field winding is not energized by current.
The Pole is made with two parts. The Pole core and Pole shoe are connected through hydraulic pressure. Motor pole is connected to the Yoke of the DC motor.
Armature Windings
The Armature Winding is made with Lap winding and wave winding. The Armature winding can bring a change in the magnetic field. It leads the Armature current to reduce the voltage. As this part is connected to the Rotor, the rotor moves in the direction of magnetic current.
So, when the magnetic field current is changed, the direction of the rotor will also be changed.
Commutator
The Commutator is a ring made of copper segments. It is located between the Rotor and Field windings. The Armature current has to keep creating constant torque in the same direction. The work of a Commutator is to make sure that the magnetic current is flowing in the same direction.
The Commutator makes use of a coil by making it flow backward and towards. It makes sure that the Armature current is flowing in one direction and maintaining torque.
Brushes
The Brushes are current conducting material that helps the current to flow through the Armature. The brush transfers electrical current to the Armature. Then it starts to act like a magnet.
Field Windings
The Field Windings are made of Copper wires. These Field Windings create an electro-magnet that produces field flux. When the field flux is energized, the rotor inside the field flux starts rotating.
Yoke
The Yoke works as a protector. It keeps the DC motor parts away from any kind of damage. It is basically a frame that covers the elements of the DC motor. Yoke houses the field windings
Rotor
The Rotor is the part that forces the machine to move. It receives electrical energy and converts it to mechanical energy. Hence it makes mechanical rotations for a machine to work properly.
Bearings
The bearings of a DC motor support the rotor’s shaft to make rotational movement. They maintain a consistent air gap between Rotor and the Stator.
End plates
The End plates support the bearing to maintain the connection between the stator and rotor. They are located at the end of a motor frame. These plates are removable. So you can clean them whenever you want.
Which Material Is Used for Starting Resistance of DC Starter?
The material Manganin is used for the starting resistance of a DC motor. The material used in the resistor highly affects the machine’s performance. Hence, using the right material for the resistance of the DC starter is necessary. Here are some reasons why this material is used in making resistance:
- The material Manganin gives high resistivity. The resistor can tolerate high voltage no matter how much current the DC motor is producing. Therefore, using the Manganin can help to make a safe and good resistor
- Thermal stability makes sure that the resistor is not getting overheated due to the voltage. If there is no thermal stability, the resistor won’t be able to withhold the temperature of the circuit. Hence, thermal stability is needed to ensure the resistor works well
Difference Between 3 Point Starter and 4 Point Starter
The 3-point starter and 4-point starter are used in the DC shunt motor series. While both of the starters have the same starting process, there are some key differences to be noticed. Here is a table describing the difference between a 3-point and a 4-point starter:
| Names | 3 Point Starter | 4 Point Starter |
| Terminals | There are three terminals in the 3-point starter. They are named as (L, A,F) Line terminal, Armature terminal, and Field terminal | There are four terminals in the starter. They are known as Line terminal, Armature terminal, field terminal, and NVC (No Volt Coil in Starter) |
| Line | The 3-point starter is connected to the series with a field coil | The 4-point starter is connected to the parallel with the field coil |
| Compatibility | Good for DC shunt motors | Good for DC series motor. Although it can be used in DC shunt motors as well |
| Voltage coil | There is a voltage coil that is connected to the series | There is no voltage coil. The circuit of the starter is connected directly to the parallel line to supply voltage |
What Is the Necessity of a Starter for DC Motor?
A starter is a must-have to start a DC motor. Well, it is possible to start a DC motor without the starter. But it’s not a good idea. So, you may want to know, what is the necessity of a starter? The starter helps a DC motor to control the current. If you run the DC motor without a starter, the DC motor can get an overflow of current.
It will lead to the DC motor to start abruptly or damage the wiring. Hence, the DC motor will stop working. Here are the following consequences that may occur if you run a DC motor without a starter:
- The DC motor wirings can overheat due to overflow of current in the circuit
- The motor’s combustion materials may get destroyed due to the excessive current. It can potentially lead to fire
- The DC motor will stop working completely
Identify The Components of the Basic Motor Starter
Earlier, you have known about the components of the DC motor. But it is also important to recognize the part of the basic motor starter. Please check out below to learn about it in detail:
Overload Relays
An overload relay is a switch that helps the circuit from overload. It protects the motor from overheating. Moreover, it does not completely turn off your device. Rather it helps to give the signal when the electrical power has reached a limit. Overload relays are important as they save your machine from damage.
Contactors
The work of contractors is to open and close a circuit repeatedly. It is a relay that makes the electric current go off and on. The contactor coil receives voltage from the contactor that closes contacts or opens them.
Solenoid
The starter Solenoid is a coil that connects the starter battery to the motor. The applied voltage diverts from the battery to the motor which leads the motor to get started by receiving the electrical current.
Motor Circuit Breakers
The Circuit Breaker protects the motor from overload, short-circuit, and current loss. They are electromechanical protection devices for the main circuit. It saves the equipment from high voltage.
Starter Motor Armature
The Armature is an electromagnet that rotates. Armature is an internal component of the starter. It is wrapped with conductors and windings. It is a turning coil that forces the motor shaft to spin.
Conclusion
As you already know the importance of a starter in a DC motor, you must choose the best ways to start the motor. The important part is how much it can put resistance perfectly in the circuit to control the current. End of the day, it depends on what kind of DC motor starter you want.
Moreover, you also should make sure about the starter’s quality. If the starter has an issue with circuits, it may lead to potential damage to the DC motor. However, here I have discussed how to start a DC motor with its best methods. I hope this article helps you to learn about it all.