What is an electromagnetic brake?
Think of a coiled coil like a horseshoe magnet with a north and south pole. If a piece of iron comes in contact with both poles, a magnetic circuit is created. When electricity is applied, a magnetic field is created, this field (flux) overcomes the air gap between the field and the armature. This magnetic attraction pulls the armature in contact with the brake field surface. Friction and the strength of the magnetic field is what stops the spinning motion. Almost all the torque is caused by the magnetic attraction and the friction coefficient between the armature steel and the rotor steel with the brake field.
Copper (sometimes aluminum) magnet wire is used to form the coil, which is held in place by epoxy/glue in the electromagnet (bobbin). For most industrial brakes, friction material is placed on the coil and placed between the inner and outer poles. The friction material is flush with the brake surface, as we must have metal-to-metal contact between the coil shell and the armature.
how electromagnetic brake works
In the brake, there are only three main parts. field, armature and hub (which is the brake input). Usually the magnetic field is bolted to something solid (or has a torque arm). So when the armature is attracted to the field, the stopping torque is transferred to the field housing and reduces the load. This can happen very quickly, but the braking time can be controlled by the amount of voltage/current applied to the field. When the field begins to decay, the flux will drop rapidly and the armature will disconnect. In most electromagnetic brakes, springs hold the armature away from the braking surface where the power is released, creating a small air gap.
Electromotor brake types consist of a fixed electric magnet. When buying an electric motor, you should pay attention to the type of brake. Also, an armature is wound on a flat spring and then riveted to a spindle hub. A hub is connected to the machine shaft with a key connection. By applying an electric force to an electromagnetic coil, a magnetic field is created. The magnetic force is strong enough to deflect the smooth spring and pull the armature into the magnet plate through a small air gap. The frictional connection between the magnet and the armature slows down and stops the rotating shaft. When the magnet is de-energized, the smooth spring pulls the armature across the air gap and away from the magnet plate. With an air gap between the magnet and the armature, the shaft can rotate freely without any residual tension.
The principle of electromagnetic braking is based on the conversion of kinetic energy into thermal energy. When the brakes are applied, a stopping force many times greater than the force moving the car or vehicle is applied, dissipating the corresponding kinetic energy as heat.
stop time
In the primary electromagnetic brake, two engagement times should be considered. The first is the time it takes for a coil to develop a magnetic field strong enough to pull in the armature. In this scenario, there are two effective factors; The first is the amount of turns in a coil, which determines how fast a magnetic field is created. The second case is the air gap, which is the space between the armature and the brake plate, because the magnetic lines of flux weaken rapidly in air. The farther the absorbent part is from the coil, the longer it takes for that part to overcome the air gap and be absorbed.
The second factor is much more important than the magnet wire or the air gap; Calculate the amount of inertia that the brake needs to slow down. Many customers refer to this time as downtime. In fact, downtime is the factor that the end customer cares about the most. Once it is determined how much inertia is required to start or stop the brake, the appropriate size of the brake can be selected.
