Now available in the UK from Lenze, the new BFK468 electromagnetic spring-applied brakes from Intorq are suitable for safety critical applications such as cranes and hoists. Without power applied, the brakes are engaged and generating torque, only releasing when power is restored. They feature multi-pole technology, which achieves high torque without necessarily increasing the diameter of the brake. These devices can be used statically as holding brakes, or dynamically for service and emergency duties.
The BFK468 brakes exchange the traditional single donut shaped coil for six individual coils positioned around the body. The result is an increase in magnetic flux from the greater number of coil turns, allowing higher spring forces and therefore higher torques. Multi-pole technology is best suited to larger brakes and Intorq offers four sizes. The smallest, with a body diameter of 220mm, has a rated torque of 150Nm, which can be increased to 300Nm for holding and emergency top duties. The largest, size 31, has a diameter of 390mm and a maximum torque of 2,400Nm. Compared with standard spring-applied brakes, Lenze claims this represents an increase of 100% size for size.
Brake options available include a manual release lever, external protective rubber seal, aluminium cover to give IP65 protection and a microswitch to monitor either brake status or the wear limit. Half wave and full wave rectifiers are available for dc supply with ratings up to 3A.