Brakes and Clutches
Hysteresis Advantages

Advantages of Hysteresis Devices

Unlike many other torque control devices, Magtrol hysteresis devices provide absolutely smooth, infinitely controllable torque loads, independent of speed, and they operate without any physical contact of interactive members. As a result, with the exception of shaft bearings, there are no wear components. This provides such advantages as: longer expected life, superior torque repeatability, life cycle cost advantages, broad speed range, excellent environmental stability, and superior operational smoothness.
Long, Maintenance-Free Life Magtrol hysteresis brakes and clutches produce torque strictly through a magnetic air gap, making them distinctly different from mechanical-friction and magnetic particle devices. As a result, hysteresis devices typically have life expectancies many times that of friction and magnetic particle devices.
Life-Cycle Cost Advantages While the initial cost of hysteresis devices may be the same or slightly more than that of their counterparts, the high cost of replacing, repairing and maintaining friction and magnetic particle devices often makes hysteresis devices the most cost-effective means of tension and torque control available.
Excellent Stability Magtrol hysteresis devices can withstand significant variation in temperature and other operating conditions. In addition, because they have no particles or contacting active parts, hysteresis brakes and clutches are extremely clean. Magtrol devices are used in food and drug packaging operations, in clean rooms, and environmental test chambers.
Superior Torque Readability Because torque is generated magnetically without any contacting parts or particles, hysteresis brakes and clutches provide superior torque repeatability. Friction and magnetic particle devices are usually subject to wear and aging with resultant loss of repeatability. Magtrol devices will repeat their performance precisely, to ensure the highest level of process control.
Broad Speed Range Magtrol hysteresis devices offer the highest slip speed range of all electric torque control devices. Depending on size, kinetic power requirements and bearing loads, many Magtrol brakes can be operated at speeds in excess of 10,000 rpm. In addition, full torque is available even at zero slip speed and torque remains absolutely smooth at any slip speed.
Operational Smoothness Because they do not depend on mechanical friction or particles in shear, hysteresis brakes are absolutely smooth at any slip ratio. This feature is often critical in wire drawing, packaging and many other converting applications.

Magnetic Particle Brakes and Eddy-Current Brakes
Hysteresis Brakes are often confused with magnetic particle brakes and eddy current brakes, both of which operate and perform differently than Hysteresis Brakes.
Magnetic Particle Brakes Eddy Current Brakes
Unlike Hysteresis Brakes, magnetic particle brakes have a free flowing metal powder in the air gap. When a magnetic particle brake is energized, the particles form chains along the magnetic field lines linking the rotor to the housing. As the rotor rotates, the chains continuously shear, generating torque and heat. While magnetic particle brakes are capable of producing high torque, the friction between the particles can result in poor stability and repeatability, along with a high residual drag. Eddy current brakes develop torque by the direct magnetic linking of the rotor to the stator. This linking generates eddy currents in the driven rotor. Eddy current brakes must have a slip between the rotor and the stator to generate torque.
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