What is Dynamic Braking : Working & Its Applications

It is frequently essential in several applications to prevent a running electric motor quite fast. We know that any rotary object attains kinetic energy (KE). Thus, how quick we can carry the object to break will basically depend upon how rapidly we can take out its kinetic energy. If we end pedaling the cycle, then it will ultimately stop after rotating some distance. The early KE will be stored and dissipates like heat within the resistance of the path. But, to stop the bicycle fast, then the brake is applied. Therefore stored kinetic energy will dissipate in two ways, one is at the interface of wheel brake shoe & the other one is at the interface of road-tier. But normal maintenance of the brake is necessary. This article discusses an overview of the dynamic braking of the DC motor and it’s working. Basically, there are three types of braking methods are used in a DC motor like regenerative, dynamic, and plugging.

What is Dynamic Braking?

Definition: The dynamic braking is also known as rheostatic braking. By using this, the direction of torque can be reversed for breaking the motor. When the motor is running condition, it is disconnected through braking from the power source & it can be connected across a resistance. Once the motor is detached from the source, then the rotor starts rotating because of inactivity & functions like a generator. So once the motor functions like a generator then the current flow & the torque will be reversed. Throughout braking, sectional resistances will be cut-out to keep the steady torque.

Dynamic Braking of DC Motor

If an electric motor is simply detached from the power supply, then it will stop but for large motors, it will take a longer time due to high rotating inertia because the energy which is stored has to dissolve throughout bearing & wind friction. The condition can be enhanced by pushing the motor to function as a generator through braking; a torque opposite to the path of rotation will be forced on the shaft, thus helping the device to come to discontinue rapidly. Throughout the braking action, the early KE which is stored within the rotor is either dissolute in an exterior resistance otherwise fed back to the power supply.

Connection Diagram of Dynamic Braking of DC Shunt Motor

In this kind of braking, the dc shunt motor is detached from the power supply & a braking resistor (Rb) is connected across the armature. So this motor will function as a generator to generate the braking torque.

Throughout this braking, once this motor functions as a generator, then K.E (kinetic energy) will store within the rotary parts of the DC motor. The load which is connected can be changed into electrical energy. This energy will dissipate like a heat within the braking resistance (Rb) & the resistance of the armature circuit (Ra). This kind of Braking is an ineffective method of braking because the energy which is generated will dissipate like heat within the resistances.

The connection diagram of the dynamic braking of a dc shunt motor is shown below. From this diagram, the braking method can be understood. In the following diagram, the switch ‘S’ is a DPDT (double pole double throw).

In a common motoring method, switch ‘S’ is connected to two positions like 1& 1′. The supply voltage including polarity and external resistance (Rb) is connected across 2 & 2′ terminals. But, in motor mode, this circuit part remains stationary. To start braking, the switch is thrown in the direction of positions 2 & 2′ at t = 0, thus detaching the armature as of the supply of left hand. The armature current at t = 0+ will be Ia = (Eb + V)/(ra + Rb) because ‘Eb’ & the voltage supply from the right hand have preservative polarities through the good features of the connection.

Here the direction of ‘Ia’ can be reversed by generating ‘Te’ within reverse direction toward ‘n’. Once the ‘Eb’ decreases, ‘Ia’ decreases with time while speeding decreases. But, ‘Ia’ cannot turn into zero at any time because of the occurrence of the voltage supply. So dissimilar to rheostatic, an extensive magnitude of braking torque will exist. Therefore, stopping the motor is probably faster compare with rheostatic braking. However, if the switch ‘S’ constant within the positions of 1′ & 2′ & even after zero speed so the machine will begin picking up speed within the opposite direction to work as a motor. So maintenance must be taken for detaching the supply at the right hand, and then the armature speed moment will become zero.

Advantages & Disadvantages

The advantages and disadvantages are

• This is a much-used method where en electric motor is worked as a generator once it is detached from the power source
• In this braking, the energy which is stored will dissipate through the resistance of braking & other components used in the circuit.
• This will reduce braking components based on wear on friction & regeneration reduces the usage of net energy.

Applications of Dynamic Braking

The applications include the following.

• The dynamic braking technique is used to stop a DC motor & widely used in industrial applications.
• These systems are utilized in the applications of fans, centrifuges, pumps, rapid or continuous braking, and certain conveyor belts.
• These are used where rapid slow down & reversing are required.
• These are used on railcars through several units, trolleybuses, electric trams, light rail vehicles, hybrid electric & electric automobiles.

FAQs

1). What is an alternate name of DC dynamic braking

It is also known as rheostatic braking.

2). What are the types of braking

They are regenerative, dynamic & plugging.

3). What is DBC (dynamic brake control)?

The DBC immediately builds up the utmost brake force to stop the vehicle.

4). What is the difference between dynamic & regenerative braking?

The energy stored within the dynamic braking will dissipate during the braking resistance as well as other components within the circuit, whereas in regenerative, the energy which is stored will be sent back toward the power source so that it can use it again later.

Thus, this is all about an overview of dynamic braking. This system is used to reverse the torque direction as well as for breaking the motor by disconnecting it from the power source across the resistance. Here is a question for you, what are the different types of braking?