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The MagnaDrive Adjustable Speed Drive: How Does It Work? The MagnaDrive Adjustable Speed Drive (ASD) works by transmitting torque from the motor to the load across an air gap. There is no mechanical connection between the driving and driven sides of the equipment. The torque is created by the interaction of powerful rare-earth magnets on one side of the drive with induced magnetic fields on the other side. By varying the air gap spacing, the amount of torque transmitted can be controlled, thus permitting speed control. The MagnaDrive ASD consists of three sets of components. A magnet rotor assembly, containing rare-earth magnets, is attached to the load. A copper conductor rotor assembly is attached to the motor. Actuation components control the air gap spacing between the magnet rotors and the conductor rotors. Relative rotation of the copper conductor and magnet rotor assemblies induces a powerful magnetic coupling across the air gap. Varying the air gap spacing between the magnet rotors and the conductor rotors results in controlled output speed. The output speed is adjustable, controllable, and repeatable. Sectioned Side View of a MagnaDrive ASD

The principle of magnetic induction requires relative motion between the magnets and the conductors. This means that the output speed is always less than the input speed. The difference in speed is known as slip. Typically, when the MagnaDrive ASD is operating at full rated motor speed, the slip is between 1% and 3%. The output torque of a MagnaDrive ASD is always equal to the input torque. The motor is only required to produce the amount of torque needed by the load. The efficiency of the system is calculated by dividing the output (load) speed by the input (motor) speed. The ability of the ASD to transmit power or to control speed is not affected by minor angular or offset alignment between the motor and load. Vibration due to misalignment is virtually eliminated. Transmission of vibration across the drive is also eliminated due to the air gap configuration. When installed in a system, the MagnaDrive ASD is controlled from a process signal. The pressure, flow, level or other process control signal is provided to the MagnaDrive ASD actuator. The drive will then modulate the speed of the load to satisfy the control needs. The MagnaDrive ASD is easily retrofitted to existing installations. No modifications to the power supply are necessary, minimizing capital and installation costs. No Electro-Magnetic Interference (EMI) or Harmonic Distribortion is created by the system. In many cases, the existing process control hardware can be inactivated or removed. The load is operated at its optimum speed, increasing energy efficiency and reducing operating and maintenance costs.

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