Dynamic Braking | Braking Resistor | Regenerative Braking | What is Regenerative Braking | How does Regenerative Braking Work

There are several types of braking in electrical systems, depending on the application and the type of motor being used. Dynamic braking is often used in applications where the motor needs to be stopped quickly, such as in cranes, hoists, and other machinery that requires precise control over stopping and starting. Dynamic braking resistors are used in electric motors that do not have a built-in braking mechanism. Here are some of the most common types of braking:

Dynamic Braking: 

This is a braking method used in DC motors and in AC motors with a variable frequency drive (VFD). Dynamic braking involves applying a DC voltage to the motor winding after the power has been removed, which creates a magnetic field that opposes the rotation of the rotor and slows it down.

What is a Braking Resistor?

A braking resistor is a component of an electric motor control system that dissipates the excess energy generated during deceleration or braking. When an electric motor stops or slows down, the kinetic energy of the rotating load is converted into electrical energy, which is fed back to the motor control system. If this energy is not dissipated, it can damage the motor and the control system. A braking resistor provides a path for this excess energy to flow, dissipating it as heat and preventing damage to the motor and the control system.

 How Does a Braking Resistor Work?

When an electric motor is decelerated or stopped, the voltage across its terminals reverses, and it starts acting as a generator, generating electrical energy. This electrical energy flows back to the motor control system and needs to be dissipated to prevent damage to the motor and the control system. A braking resistor provides a path for this energy to flow and dissipates it as heat. The braking resistor is connected across the motor terminals, and when the motor generates excess energy, it flows through the braking resistor, dissipating as heat.

Dynamic Braking Resistors

Dynamic braking resistors are used in electric motors that do not have a built-in braking mechanism. These resistors are connected across the motor terminals and dissipate the excess energy generated during braking. Dynamic braking resistors are simple and cost-effective but are not suitable for high-power motors.

Applications of Braking Resistors

Braking resistors are used in various applications where an electric motor needs to be stopped or decelerated quickly and accurately. Some of the most common applications include:

Elevators and Escalators

Elevators and escalators use electric motors to control their motion. When an elevator or escalator stops or decelerates, the kinetic energy of the moving load is converted into electrical energy, which needs to be dissipated. Braking resistors provide a path for this energy to flow, dissipating it as heat.

Cranes and Hoists

Cranes and hoists use electric motors to lift heavy loads. When a crane or hoist stops or decelerates, the kinetic energy of the load is converted into electrical energy, which needs to be dissipated. Braking resistors provide a path for this energy to flow, dissipating it as heat.

Electric Vehicles

Electric vehicles use electric motors to drive their wheels. When an electric vehicle stops or decelerates, the kinetic energy of the vehicle is converted into electrical energy, which needs to be dissipated. Braking resistors provide a path for this energy to flow, dissipating it as heat.

Industrial Machinery and Automation

Industrial machinery and automation use electric motors to control their motion. When an industrial machine or automation system stops or decelerates, the kinetic energy of the moving load is converted into electrical energy, which needs to be dissipated. Braking resistors provide a path for this energy to flow, dissipating it as heat.

Advantages of Braking Resistors

Braking resistors offer several advantages, including:

• Preventing damage to the motor and control system by dissipating excess energy generated during deceleration or braking
• Improving the accuracy and efficiency of motor control by preventing overshoot and undershoot
• Reducing downtime and maintenance costs by preventing damage to the motor and control system
• Enhancing safety by providing a reliable and effective means of controlling motor speed and motion

Factors to Consider When Choosing a Braking Resistor

When choosing a braking resistor, several factors need to be considered, including:

Power Rating

The power rating of the braking resistor should be higher than the motor's power rating to ensure that it can dissipate the excess energy generated during deceleration or braking.

Resistance Value | Braking Resistor Value Calculator

The resistance value of the braking resistor should be carefully selected to ensure that it can dissipate the excess energy generated during deceleration or braking without overheating.

When selecting a braking resistor for an electric motor control system, it is important to calculate the appropriate resistance value to ensure that the resistor can safely dissipate the excess energy generated during deceleration or braking.

The braking resistor value can be calculated using the following formula:

R = V^2 / P

Where R is the resistance value in ohms, V is the DC bus voltage in volts, and P is the power rating of the motor in watts.

For example, if the DC bus voltage is 500V and the motor power rating is 10kW, the braking resistor value can be calculated as follows:

R = (500)^2 / 10,000

R = 25 ohms

This means that a braking resistor with a resistance value of 25 ohms or higher should be selected for the motor control system.

It is also important to consider the power rating of the braking resistor to ensure that it can safely dissipate the excess energy generated during deceleration or braking. The power rating of the braking resistor should be equal to or greater than the power rating of the motor.

Temperature Rating

The temperature rating of the braking resistor should be high enough to withstand the heat generated during braking.

Mounting and Enclosure

The braking resistor should be mounted in a suitable location and enclosed to protect it from the environment and prevent accidental contact.

Dynamic braking is a method of electric braking used in DC motors and in AC motors with a variable frequency drive (VFD). When the motor needs to be stopped quickly, dynamic braking is applied by short-circuiting the motor windings and converting the kinetic energy of the motor into electrical energy. This creates a magnetic field that opposes the rotation of the rotor and slows it down. The electrical energy generated during dynamic braking is dissipated as heat in a braking resistor or is fed back into the power supply.

One of the advantages of dynamic braking is that it can be used to stop the motor quickly and safely, without causing damage to the motor or the surrounding equipment. However, it can also generate high currents and stresses on the motor, which can cause overheating and damage over time. For this reason, dynamic braking should be used only when necessary, and appropriate measures should be taken to protect the motor and the braking resistor from excessive heat and stress.

Regenerative Braking | What is Regenerative Braking | How does Regenerative Braking Work

This is a braking method used in AC motors with a VFD. Regenerative braking involves using the motor as a generator to convert the kinetic energy of the motor into electrical energy, which is then fed back into the power supply or stored in a braking resistor.

Regenerative braking is a method of electric braking used in AC motors with a variable frequency drive (VFD). When the motor needs to be slowed down or stopped, the VFD changes the direction of the motor's rotating magnetic field, causing the motor to act as a generator and convert the kinetic energy of the motor and load into electrical energy. This electrical energy is fed back into the power supply, where it can be used by other equipment or stored in a battery.

Regenerative braking is particularly useful in applications where the motor is frequently starting and stopping or where the motor is driving a heavy load that needs to be slowed down or stopped quickly. It is often used in industrial machinery, such as cranes, hoists, and conveyor systems, as well as in electric vehicles, where it can help extend the range of the vehicle's battery.

One of the advantages of regenerative braking is that it can help to reduce energy consumption and operating costs by capturing and reusing energy that would otherwise be wasted as heat. However, it can also generate high voltages and currents, which can cause damage to the motor and the surrounding equipment. For this reason, appropriate measures should be taken to protect the motor and the power supply from excessive voltage and current, such as using a braking resistor or a regenerative braking system with a DC bus voltage that is matched to the power supply.

Plugging Braking: 

This is a braking method used in DC motors. Plugging braking involves reversing the direction of the voltage applied to the motor, which causes the motor to stop rapidly. This method is generally used for emergency stops and can cause high currents and stresses on the motor.

Mechanical Braking: 

This is a braking method that involves using a mechanical braking system, such as a brake pad or brake disc, to slow down the motor. This method is commonly used in applications where precise control over the braking force is required, such as cranes and hoists.

Electromagnetic Braking: 

This is a braking method that uses an electromagnetic field to slow down the motor. This method is commonly used in applications where the braking force needs to be precisely controlled, such as elevators and escalators.

The selection of the braking method depends on the application, the type of motor, and the desired level of control over the braking force.

FAQs

What is dynamic braking?

Dynamic braking is a braking technique used in electric motor control systems to rapidly stop a motor by converting its kinetic energy into electrical energy, which is dissipated through a braking resistor.

How does dynamic braking work?

When a motor is decelerating or braking, it generates excess energy that needs to be dissipated to prevent damage to the motor and control system. In dynamic braking, a braking circuit is activated to switch the motor from a power-generating mode to a braking mode, and the kinetic energy of the motor is converted into electrical energy, which is then dissipated through a braking resistor.

What is a braking resistor?

A braking resistor is an electrical component that is used to dissipate excess energy generated during deceleration or braking of an electric motor.

Why do electric motors need braking resistors?

Electric motors need braking resistors to dissipate the excess energy generated during deceleration or braking, preventing damage to the motor and control system, and enhancing safety.

What are the applications of braking resistors?

Braking resistors are used in various applications, including elevators and escalators, cranes and hoists, electric vehicles, and industrial machinery and automation.

How do you choose a braking resistor?

When choosing a braking resistor, several factors need to be considered, including power rating, resistance value, temperature rating, and mounting and enclosure.