Motor brake relays are used with view to safety and efficiency. With braking currents up to 600 A DOLD braking units allow a reliable deceleration of asynchronous motors up to 160 kW. They can be used to bring your machines to a standstill within 10 s as required by the European Directive on Machinery.
... at a glance
Easy installation, also in existing plants
Free from wear and maintenance
Adjustable braking currents allow optimal tailoring to machines and plants
Automatic zero-speed monitoring ensures precisely accurate braking current cutoff and spares time-consuming readjustments
Thermistor motor protection prevents inacceptable motor heating
Wide voltage ranges allow a versatile use of the braking units
What is DC Injection Braking?
DC Injection braking is an effective electrical method of stopping a rotating AC asynchronous motor.
How does it work ?
An AC electrical motor works on the basic principle of opposing magnetic poles attracting each other. If you create a rotating magnetic field in the stationary (stator) windings of a motor, a magnetic field of the opposite polarity in the rotating (rotor) windings will naturally want to follow it trying to align itself (Fig.1).
Fig.1 The Rotor will follow the rotating magnetic field in the Stator windings.
If you were to then create a stationary magnetic field in the stator, the attracted opposing fields in the still rotating rotor windings will try to align themselves with the stationary field, creating a strong braking force. This is what happens when a DC current is Injected into the Stator windings of a motor.