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Integrated actuator provides simple all-in-one motion

11 February 2013

Olsen Engineering has introduced the new Exlar Tritex II dc TDM/X integrated actuator to the UK market. Already available in ac rotary and linear versions, this new product operates from 12V, 24V, 48V and 60V dc supplies in five different motion modes. The standard package features a fully integrated energy efficient permanent magnet (PM) motor, high resolution position controller and amplifier.

The Tritex II has a built-in, non-volatile memory that stores programmed functions for linear and rotary motion control applications, product configurations and motion parameters. For commissioning, Olsen offers free ‘Expert’ software for a variety of actuator applications, configuring position or force control using a 0-10V or 4-20mA analogue control signal or digital inputs.

A more recent development is provision of EtherNet IP fieldbus options amongst others. An onboard RS/485 interface is a standard feature, providing control, programming and monitoring of all motor functions and actuator movements. Olsen Engineering UK’s Piers Olsen describes a recent application of the Tritex II, which enables stators to be wound to any speed and torque, depending upon the end-use requirements:

“We have just won a project from a hydro turbine operator to supply an actuator which has an internal spring for failsafe operation to open or closed positions. This is pretty unique for process control with valves. If the mains power fails, for mission critical applications it would be backed up by UPS power anyway but if, in the unlikely event, the drive electronics fails in the actuator, we have an internal spring option which allows the operator to select whether it fails open or closed. Tritex II TDM/X is also available with an electromagnetic PM holding brake option, to allow it to stop working at a fixed position even under full load conditions.

Another alternative configuration available on the Tritex II is a manual override that disables the actuator and enables it to be moved using either a hand wheel or a side hex drive operated by a standard socket wrench. The hand wheel has an integrated 3:1 planetary gearbox so it is easy to move by hand; a more typical arrangement for products of this type is to use 1:1 worm gear, which requires much more effort.

Bearing in mind the process valve application, it is worth noting that the Exlar Tritex II actuator is Class I Division 2 explosion proof rated for hazardous areas, with ATEX certification planned for next year. Ingress protection to IP54 or IP65 is available, and Olson says the actuator even passes IP67 tests. A subsea variant that can operate at depths of 3,000m is also available.

In addition to the standard front-protective bellows, a high temperature Teflon-coated fibreglass version is available, rated to 260oC, while low temperature grease allows operation from -40oC. The actuator housing and main rod are of stainless steel, but different coating options are available, including a Type III hard coat and food grade white epoxy. In addition, mounting arrangements and main rod dimensions can be customised according to application requirements. Piers Olsen again:

“Tritex II is based on the same inverted planetary roller screw design as used on the GSX, GSM and I Series. Because of the annular groove engaging spurs design there is no conflicting friction and the load is transmitted evenly across the central pinion, providing efficiencies in excess of 85 percent and five times the travel life compared with that of an equivalent ball screw. Moreover, the bearings are preloaded and heat shrunk to the housing, avoiding adhesive issues.

“And with the Tritex X series, which has ten spurs, you get fifteen times the travel life for little additional cost. What this means is that instead of a ball screw actuator lasting twelve to eighteen months, Exlar II will generally last for more than ten years.”

According to Olsen Engineering, PM electric actuators are proved to consume at least eleven times less energy than pneumatic cylinders and 4.4 times less energy than a hydraulic cylinder, while offering the advantage of little or no maintenance and repeatable, smooth positioning/applied force. 

Offering a reliable method of controlling linear movement, Exlar's range of roller screw linear actuators offer thrusts of up to 370kN, 8m travel and max speeds of 1.5m/s with 25m/s² acceleration/deceleration. An Exlar Energy Efficiency White paper is available upon request.

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