The Eddy Current Drive (ECD) offers versatility and simplicity to any application where accurate, easily controlled adjustable speed is required from an AC power source. The ECD features:

     The basic EDDY Current Drive consists of an AC motor, eddy current clutch and speed controller. The simplicity of our design is what makes it so reliable; there is no electrical connection to any rotating part and the only mechanical connection between the rotating members is through one ball bearing. Clutch and motor are self-air cooled with maximum ventilation at all speeds. No maintenance is required beyond routine bearing lubrication; there are no brushes or slip rings to replace

How It Operates
     Driven at a constant speed provided by an AC induction motor (or optional coupled or belted input), the input fan/pole assembly rotates inside the stationary field coil to generate a rotating magnetic AC flux for the small diameter, low-inertia output rotor assembly. This flux generates eddy currents in the output rotor when a difference in input and output speed exists. These eddy currents produce their own magnetic fields which are attracted to the originating field, resulting in an output torque transmitted in the same direction of rotation as the input pole assembly. (figure 2)

Transmitting Torque
     The amount of torque transmitted from input to output is proportional to the voltage applied to the stationary field coil (strength of the magnetic field) and the relative speed between the constant speed input assembly and the low-inertia output rotor. (figure 1). Torque transmitted is typically limited to the maximum motor torque available.

Speed Control
     Sensing output speed, using an AC tachometer, and suitably controlling the stationary coil voltage can regulate the output speed of the drive regulated to the desired speed. The controller will automatically maintain this speed (within 1%) even if the load varies.

Performance
     Figure 1 represents a set of torque/speed capability curves for an Eddy Current Drive. The torque capability of the drive depends on the clutch coil excitation voltage. As the coil excitation is increased to 100% the torque capacity increases as shown by the yellow curves.
     The green bar represents the maximum permissible full load operating range of the clutch. This corresponds to the continuous duty speed range shown on the clutch nameplate. Adjusting the speed control potentiometer with a constant torque load means the speed will change along this green bar.
     When the potentiometer is set at a given point, such as 100% shown in figure 1, the speed remains constant within 1% as the load varies. This is illustrated by the blue bar. The control automatically adjusts coil excitation to keep speed constant.
     The curves also illustrate the high overload capacity of the Eddy Current Drive. On every rating, this torque capacity exceeds the motor breakdown torque (Motor BDT).

 

Figure 1 (click to enlarge)	Figure 2 (click to enlarge)