Product category:
Drives, motors and power transmission, couplings, clutches
News Release from: ZF Great Britain | Subject: Hysteresis brakes and clutches
Edited by the Manufacturingtalk Editorial
Team on 15 June 2001
Hysteresis brakes and clutches replace
servos
The ability of ZF's unique hysteresis brakes and clutches to perform precise tension control operations on larger systems has been enhanced with the introduction of new high power brakes.
The ability of ZF's unique hysteresis brakes and clutches to perform precise tension control operations on larger systems has been enhanced with the introduction to the range of new high power brakes These can operate with twice the slip power (up to 2000W) of existing units and up to 4 times the slip power for brief (peak) periods
This article was originally published on Manufacturingtalk on 19 Feb 2002 at 8.00am (UK)
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The hysteresis brakes and clutches provide a cost effective and much simpler alternative to servo systems in precise tension control applications.
Their exact control, and the unique combination of contact free and, therefore, wear free torque transmission, is ideally suited to all manufacturing processes where control of tension is required, e.g the production of endless products such as wire, cable paper and foil.
One of the major advantages of the hysteresis brakes is that they transmit torque via a magnetic flux.
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A combination of Brakes and clutches managed by ZF's ERM controllers has proved to have the accuracy and reliability to replace DC drive based tension control systems in presses at Day International.
Consequently, there is no physical contact and none of the usual disadvantages resulting from friction.
There is also no fluctuation in friction levels due to external influences, no stick-slip effect and no wear during slip operation.
The hysteresis brakes are used mostly in slip mode, but they also have a holding torque.
In contrast, the clutches transmit torque in both synchronous and slip modes.
A major benefit is that the torque transmitted is dependent only on the current though the armature coil and is virtually speed independent.
The torque is continuously variable and is controlled precisely from zero to the maximum.
The level of equipment and time required to set-up the hysteresis brakes and clutches in comparison with servo systems is minimal.
The slip and synchronous torques of the brakes and clutches are simply set manually in the range from zero up to the maximum value.
The values depend only on the setting of the electric current in the magnetic coil.
The torque set is largely speed-independent and is also effective during standstill.
Because of these factors there are essential differences between hysteresis components and eddy-current units.
In synchronous operation and at standstill the latter units cannot transmit torques.
They are also difficult to control in the lower speed range.
The hysteresis brakes and clutches are part of ZF's Tiratron package.
This also includes a universal electronic control unit that provides users with a variety of operating options.
The simplest of these is basic open loop control, without any form of feedback.
For applications requiring more precise control a number of closed loop control options are available.
These include simple sensing with encoders, and systems with both sensing and the capability to perform calculations and provide feedback variables.
Other major options are closed loop force control, in conjunction with a dancer arm, and closed loop position control.
Hysteresis brake units in ZF high power range are available with (continuous) slip powers in the range from 250 to 2,000W.
Peak powers are twice these figures.
The hysteresis clutches for winding-on applications are supplied in four different versions with torques ranging from 0.4 to 12Nm.
The ZF Tiratron range is backed-up by the resources of one of the most respected manufacturers of driveline technology in the world.
ZF Industrial is part of the worldwide ZF Group of companies with production centres, partners and representatives on every continent.
In the industrial sector, ZF is at the forefront of developments, from individual units to complete systems solutions for all types of machinery and production units, including those used in robotic systems and the fast growing factory automation sector. Request a free brochure from ZF Great Britain ...
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