Perma-Tork® Selection Model Selection Slip Watts Two types of Perma-Torks are available: When a brake or clutch is slipping, mechanical energy is being converted to thermal energy. The rate that thermal energy is being created is expressed in terms of slip watts. Slip watts are a function of torque and slip speed. The model selected must have a dissipation rating sufficient to dissipate the slip watts created. 1. Hysteresis The hysteresis clutches and brakes offer the smoothest torque and longest life. Torque is infinitely adjustable within its range and is unaffected by speed. Hysteresis units can be mounted as clutches or brakes. Unwind Tension Control The hysteresis models do not slip unless the set torque value is reached. In some applications, such as overloaded protection applications, slip does not occur unless an "overload" takes place. As long as the system 2. Magnetic Particle is being monitored for overloads, it is not The Magnetic Particle Brakes feature high necessary to size for slip watts. torques in small packages. Torque is smooth, adjustable, and unaffected by speed. Typically, these units are mounted Selection Procedure as brakes. (Unwind Tensioning) Brake mounted on shaft or unwind spool or bobbin. Note: Tension will change as material diameter changes. If constant tension is required, it may be necessary to mount the constant torque brake on a pulley or nip roll. Information required: Full roll diameter (inch) = 6 inches Core diameter (inch) = 4 inches Average tension (lbs) = 4 lbs Velocity (feet per in/min) = 100 fpm Quick Selection Selection Criteria Torque (Constant slip applications) How to size: If you know your torque requirement and slip RPM, you can proceed directly to the quick selection charts. Average radius (in) = Full roll diameter (inch) + Core diameter (inch) 4 4 = 6 + = 2.5 inches 4 Hysteresis and magnetic particle applications. Standard selection procedure For Perma-Tork applications torque requirements must be calculated in units of pound-inches (lb-in). If the torque value is very small it may be necessary to express torque in units of ounce-inches (oz-in). Simply multiply the value in lbin by 16 to get the value in oz-in. Step 1. Torque (lb-in) Determine torque required = Avg. tension (lb) x Avg. radius (inch) Step 2. = 4 x 2.5 = 10 lb-in Determine heat dissipation required Step 3. Check tension range: Select model from specification chart Max tension = Torque (lb-in) x Nip Roll Or Pulley Tension Control 2 Core dia. (inch) = 10 x 2 = 5 lb 4 Min. tension = Torque (lb-in) x (Coil Winding) 2 Full roll dia. (inch) Pulley or nip roll diameter* = 4 inches Tension = 6 lb = 11.3 watts Velocity = 100 fpm How to size: Torque (lb-in) = Tension (lb) x Diameter (inch) 2 4 = 6 x = 12 lb-in 2 Tension (lb) x velocity (fpm) Slip watts = 44.2 = 6 x 100 = 13.5 watts 44.2 Select an HC-4 from the specification chart Select a HC-5 from the specification chart Permanent Magnet Clutches & Brakes 151 Permanent Magnet Clutches & Brakes = 10 x 2 = 3.3 lb 6 Max. tension (lb) x velocity (fpm) Slip watts = 44.2 Information required: