SynRM changes the face of constant torque in extruder applications

SynRM brings between 8 to 15 percent improvement in energy use

It took just five days to install and commission a synchronous reluctance motor (SynRM) and drive package on a twin extruder, including the removal of the old DC motor. The results for the end user, Radius Systems of Derbyshire in the UK, are good: up to 15 percent lower energy use compared to the old DC motor, a significant reduction in motor maintenance costs and a drop in audible noise.

Reducing operating costs
The three main costs faced by the plastics business are raw materials, labor and energy. Anything that can reduce such costs is looked upon favorably by the industry. Installing the SynRM package has helped to reduce labor costs by removing a maintenance routine that is essential to DC motors.

A DC motor’s operation depends on carbon brushes to conduct current between moving parts and stationary wiring. However, Radius estimates that the annual static and dynamic checks, brush changes and outsourced labor costs alone were costing it about £2,000 per motor.

Being an AC technology means that the SynRM does not require any carbon brushes and so the costs are eliminated.

Increased energy efficiency
Furthermore, retrofitting a drive and motor package to a constant torque application, such as an extruder, does not normally bring energy saving benefits. The fact that SynRM brings between 8 to 15 percent improvement in energy use – and with a return on investment within two years – shows the efficiency of the SynRM solution.

This energy saving range is due to the nature of the extrusion process, as Rob Betts, Engineering Manager at Radius Systems explains: “The actual energy saving is dependent upon several process variables such as raw material type, different product ranges and profiles, the temperature at the die and the barrel and the general ambient environmental conditions. For instance, energy consumption is higher on a cold day as more energy is needed to warm up the process.”

Deciding that the SynRM was the right solution for the extruder line was down to ABB Authorized Value Provider, Inverter Drive System, which carried out a series of “before” and “after” monitoring tests. The tests revealed that the speed range of the application’s DC motor was over-sized for the application and hence consuming more energy than necessary. Also, despite the motor having been regularly maintained, it was 20 years old and nowhere near the efficiency for which it was originally designed.

Unexpected noise reduction
The SynRM used is a 200 kW, 1500 rpm, IE4 solution, together with the ABB industrial drive, ACS880. It is proving to be a far quieter package than the existing DC motor. “SynRM has given us a reduction in noise in the production hall which is a benefit we had not expected,” says Betts. “While we have not measured the noise levels, everyone has noticed a definite reduction across the plant, which in itself is a motivational measure.”

Motor size matters
A challenge was presented by the physical footprint of the existing DC motor. “DC motors tend to be long and thin,” explains Betts, “whereas AC motors tend to be shorter but bigger in diameter.” However, SynRM can be up to two frame sizes smaller than a conventional induction motor which is a benefit in the direct replacements of DC motors.

So, would Radius Systems consider a SynRM package again? “Most definitely,” says Betts. “IE4 and higher inefficiencies are the way forward, so provided the price is competitive, the return on investment can be justified and the technology can be delivered to our time frames, then we would have no qualms about using SynRM.”

For more information about this customer case, visit our website: http://new.abb.com/drives/segments/plastics-and-rubber/case-radius-systems