High-torque electromagnetic clutches suit difficult environments

The 450 series clutches are engaged by applying a DC voltage, normally 24V DC, to a stationary coil. This generates magnetic flux which travels into the rotor, a rotating plate that forms one of the two friction surfaces. The flux then crosses an air gap and pulls another plate, the armature, into contact with the rotor generating the torque by friction. In fact the clutch is designed so that the magnetic flux crosses the air gap twice, hence the description "double flux crossed'. This doubles the attractive force, increases the torque and leads to compact dimensions. The double flux crossing is achieved by using a two-part armature with inner and outer rings, and a rotor where non-magnetic material blocks the flux from travelling radially.

A second notable feature of the 450 clutches is the fact that the friction is achieved through steel-to-steel rubbing surfaces without friction material. The rubbing surfaces, which are the magnetic poles, are gas nitrided. Wear is virtually zero provided the operating conditions meet the limits for engagement speed, energy and frequency of operation. Generally this means slip times of less than 1 second. Use of steel rubbing surfaces makes the clutches unaffected by minor contamination of oil or water - this will be quickly burnt off. In fact, they can be used even in continuous splash conditions with a suitable torque derating.

The robust nature of these clutches is proven in a variety of applications, often with diesel engines. These include the connection of pumps and compressors. Agricultural uses include potato pickers and seeding machines. The high resistance to severe environments has been used for steering disconnect on mobile cranes and a hybrid diesel/electric marine drive.

Mnninghoff 450 series clutches are also available as clutch couplings using the type 313 Hexaflex rubber disc couplings. These form a compact in-line connection with the added advantage that the Hexaflex coupling provides excellent damping of the diesel engine vibrations. Other special designs and brakes are also available.

Series 450 clutches are available in the UK from the Techdrives website www.techdrives.co.uk/.