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Product category: Industrial Drives/Controls
News Release from: ABB Automation Tech (Drives and Motors) | Subject: ACS 600 AC drive
Edited by the Engineeringtalk Editorial Team on 03 February 2000

AC drive cuts mixer's maintenance bill
by 80%

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A reduction of over 80% in maintenance costs has been achieved by replacing a star/delta starter with a variable speed drive on a breakfast cereal mixer at a leading UK supermarket food producer.

A reduction of over 80% in maintenance costs has been achieved by replacing a star/delta starter with a variable speed drive on a breakfast cereal mixer at a leading UK supermarket food producer An ACS 600 AC drive with Direct Torque Control (DTC) from ABB Industrial Systems has smoothed violent vibrations that were causing regular gearbox failures

The mixing machine consists of a rectangular stainless steel vessel, 3m high with a 1m2 base, which contains up to 1 tonne of dried cereal.

Once it has been loaded onto the mixing machine, the vessel is clamped top and bottom and rotated at 30rpm by an 11kW right-angled worm-geared motor.

An 11kW star/delta starter controlled the machine and a smaller positioning motor was used to inch the vessel into its resting position before unloading it with a forklift.

Although this arrangement could rotate the vessel, it could not control the acceleration or deceleration of the spinning load or handle the rapid changes in the torque required to turn the container as the cereal shifted from one end to the other.

These load changes created violent oscillations that were transmitted back through the gearbox causing it to fail every six months.

While the gearbox was being replaced, the factory had to use a standby mixer to maintain its production.

The solution uses an 11kW, ACS 600 AC drive from ABB Industrial Systems that was provided by Parmley Graham distributors and installed by Shropshire-based systems integrator Electrical Design and Automation (EDA).

"We had already made one attempt to control the mixer by fitting a soft start," says Neil Porteous, Managing Director of EDA, adding, "but this could not cope with the rapid changes in torque needed to keep the vessel rotating evenly.

So we conferred with Parmley Graham for a solution." Parmley Graham loaned the factory an 11kW ACS 600 with DTC to prove that it would work.

"This is something that we can do for customers who need convincing that they can get the result they want with AC drives," explains Glen Hickman, Sales Engineer at Parmley Graham.

After carrying out operational tests with the loaned ACS 600, the plant immediately ordered the drive and EDA set about creating a permanent installation.

Capable of providing full torque at zero speed, the ACS 600 with DTC has smoothed the starting process, brought the mixer's erratic movement under control and made it possible to position the mixer without an additional jockey motor.

The mechanical brake and the star/delta starter have also been removed, further reducing the total running and maintenance costs of the mixer.

"Since the drive has been installed, the factory has had no more maintenance problems with the machine's gear-box and the standby mixing machine has been decommissioned," adds Porteous.

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