Motor drivers generally are used for the control of asynchronous or synchronous motors. Thanks to the Dynamic Braking Resistors, electric motors which be controlled by drivers can be stopped, slowed down, or controlled safely in a short time. Especially big electric motors continue to rotate for a while due to the kinetic energy they have. As the rotor continues to rotate, the motor works as a generator and feeds the driver back. This situation not only increases the motor stopping time but can also cause an over voltage fault at the terminal of the DC drive and therefore the drive to protect itself. The braking resistors are a good solution to avoid this situation.

Determination of Power and Resistance Values of Braking Resistor

The resistance value of the braking resistor changes based on the drive. This can be detected by the driver's manufacturer. This value is specified in the drive's user guide. If this value is given as Rmin and Rmax, the resistance should be close to Rmin and but not lower than Rmin. Braking time extends as it gets closer to Rmax. The resistance power is determined based on the application used by the motor to which the drive is connected. It can be determined with special engineering calculations or specified by the company based on our experience on frequently used applications. In some cases, the power of resistance can be equal to the motor power, or even up to ten times smaller than it.

Applications Using Braking Resistors

Braking Resistors are used in many motor applications that are controlled by variable frequency drives.

  • Vertical and horizontal movements of cranes, portal bridge cranes, mobile cranes, and tower cranes
  • Mobile facade platforms used for construction and maintenance of buildings, facade hoists and elevators, cradle systems
  • Lifts and elevators controlled by a driver and operated by a synchronous (geared) and asynchronous (gearless) motors
  • DC and AC servo motor drives used in robot control, digital control, and position controller automation systems
  • Vertical or angular movement systems such as conveyors or loaders
  • Mixing, crushing applications at mines
  • Reel applications at cable, wire, or textile manufacturing plants
  • Factory doors controlled by motor drives
  • Machinery and presses where heavy loads are moved instantly
  • Railway vehicles and hybrid or electrical road vehicles
  • Wind turbines

What is VFD braking resistor?

VFD braking resistors are used in order to ensure fast stopping or decrease the speed of AC and DC electric motors controlled by speed drives (speed control devices). Due to kinetic energy, an electric motor continues to rotate for a short time even after it has been switched off. As the rotor keeps rotating, the motor starts acting as a generator and feeding the drive. This may not only increase the stopping time of the motor, but also cause a voltage increase on DC drive’s terminal leading to an over voltage fault and consequently a shut down. In order to avoid such problems, a breaking resistor of a proper resistance value and rated power should be connected to the DC drive’s terminal.

What is a braking resistor used for?

Braking Resistors are used in many motor applications that is controlled with driver. One of the most common application is vertical and horizontal movements of fixed cranes, portal bridge cranes, overhead travelling cranes and tower cranes. Braking resistors are used for travelling facade platforms used for construction and maintenance of buildings, facade hoists and personnel elevators, cradle systems and facade cleaning systems.
Some of other applications which braking resistor used are lifts and elevators controlled by a driver and operated by a synchronous (geared) and asynchronous (gearless) motors, machinery and presses where heavy loads are moved instantly, railway vehicles and hybrid or electrical road vehicles.

How to use braking resistor?

When the motor works as a generator, voltage increases on DC drive’s terminal leading to an over voltage fault and consequently a shut down. The braking resistor of a proper resistance value and rated power should be connected to the DC drive’s terminal. The braking resistor converts the energy released during stopping into heat energy.

How to size a braking resistor?

Resistance value of the braking resistor changes based on the drive. This can be detected by the driver's manufacturer. This value is specified in the drive's user guide. If this value is given as Rmin and Rmax, the resistance should be close to Rmin and but not lower than Rmin. Braking time extends as it gets closer to Rmax. The resistance power is determined based on the application used by the motor to which the drive is connected. It can be determined with special engineering calculations or specified by the company based on our experience on frequently used applications. In some cases, the power of resistance can be equal to the motor power, or even up to ten times smaller than it.

Braking resistors are classified in two groups based on the type of cabinet.

    1. Aluminum-Case Braking Resistors
    2. Frame Type Braking Resistors

1.Aluminum-Case Braking Resistors

The resistor made of stainless steel wire is placed in an aluminum case with a larger surface which allows good heat dissipation. The space between the resistor and the case is filled with a material that has high thermal conductivity and electrical insulation. Resistors manufactured using this technology can be used as braking resistors or capacitor discharge resistors, constant load tester, wind power plants, hybrid vehicles, and other industrial applications.
Standard resistors are 1-meter long, with fiberglass braided silicone cables suitable to rated current and cable connections resistant to high temperature. They can be manufactured with connectors or terminals on request.

 

Technical Specifications

Maximum operating voltage 1000 V
Resistance tolerance (@ 20°C) ± %5
Protection Degree IP5X
Insulation 2kV, 50/60Hz, 1min

Advantages

      • Compact sizing, option to use without a cabinet, elegant design.
      • High protection degree agains to humidity, dust, solvents and water splash
      • Excellent mechanical impact and vibration withstand.
      • Efficient design to ensure long useful life with an internal structure with high heat transmission and external structure facilitating heat transmission

2.Frame Type Braking Resistors

The resistor element is in open space and therefore these braking resistors are used inside an enclosure. “Springwound Resistor”, “Edgewound Resistor” and “Grid (Plate) Resistor” types are used on frame resistors. These resistor elements are mounted inside our standard frames in serial or parallel connections. The cross-section of the wire or the grid, loading or release of the spring, and parallel or serial connections are calculated by engineering software.

Frame type braking resistors are defined as follows according to the resistor elements type.

Resistor Element Type Code
Springwound Resistor S Series
Edgewound Resistor E Series
Grid Resistor G Series

Springwound Resistors (S-Series)

Springwound type resistor elements are used inside S-Series frame resistors. This type is perfectly suitable for short-time overloads due to its spiral form. Heated wire absorbs any expansion thanks to spiral form and gets back to its colder form. Thanks to this feature, the spring resistor ensures the safety and long operating life.

Technical Specifications

Maximum operating voltage 1000 V
Resistance tolerance (@ 20°C) ± %5
Protection Degree (Indoor Applications / Outdoor Applications) IP20 / IP23
Insulation 3kV, 50/60Hz, 1min
Frame Material (Indoor Applications / Outdoor Applications) Galvanized Steel / Stainless Steel

Advantages

      • To ensure protection degree from all directions, the bottom part of the frame is also closed and ventilated.
      • All connections are made with the electric terminal. All terminals are inside a junction box with an easy-to-remove cover.
      • Cable entries are with a waterproof brass gland.
      • Resistors are connected to the connector with a thick copper wire covered by a silicon tube or silicon glass fiber cables resistant to heat.
      • All connection elements are manufactured of non-corrosive material.
      • Our frames are designed with a special connector - junction box system. Our frames have a unique quality both visually elegant design and with friendly usage and safety.

Edgewound Resistors (E-Series)

Edgewound resistors are used for E-series frame resistors. Edgewound resistor type, the resistor element is in the form of stainless steel stripe plate. This stripe plate is wound on an electro-ceramic frame vertically. Large cross-section and the capability of fast cooling offers an optimal solution for high power - low resistance braking resistors.

Technical Specifications

Maximum operating voltage 1000 V
Resistance tolerance (@ 20°C) ± %5
Protection Degree (Indoor Applications / Outdoor Applications) IP20 / IP23
Insulation 3kV, 50/60Hz, 1min
Frame Material (Indoor Applications / Outdoor Applications) Galvanized Steel / Stainless Steel

Advantages

      • Compact and elegant frames with high cooling performance are specially designed for high power loads.
      • Available for transport with forklifts and lifting lugs at the roof.
      • All connector elements are manufactured of non-corrosive materials.
      • All terminals are inside an aluminum (IP67) junction box with an easy-to-remove cover. Cable entries are with a waterproof brass gland.
      • High-quality resistance materials are resistant to corrosion and extreme environmental conditions.
      • Special structure resistant to fast cooling, overloads, and electrical forces.

Grid Resistors (G-Series)

G series braking resistors are manufactured in blocks by connecting in series or parallel with the desired power and resistance value by the stainless steel grid type resistors specially designed according to the desired current density. They are generally used for high power and low resistance applications.

 

Technical Specifications

Maximum operating voltage 1000 V
Resistance tolerance (@ 20°C) ± %5
Protection Degree (Indoor Applications / Outdoor Applications) IP20 / IP23
Insulation 3kV, 50/60Hz, 1min
Frame Material (Indoor Applications / Outdoor Applications) Galvanized Steel / Stainless Steel

Advantages

    • Compact and elegant frames with high cooling performance are specially designed for high power loads.
    • Available for transport with forklifts and lifting lugs at the roof.
    • All connector elements are manufactured of non-corrosive materials.
    • All terminals are inside an aluminum (IP67) junction box with an easy-to-remove cover. Cable entries are with a waterproof brass gland.
    • High-quality resistance materials are resistant to corrosion and extreme environmental conditions.
    • Special structure resistant to fast cooling, overloads, and electrical forces.
Type Size Download Link
General Catalog PDF 1 MB Download
Dynamic Braking Resistors Catalog PDF 1 MB Download

 

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