Variable Speed Mixing
Date: 27 October 2003
Improving consistency and operation
When Lu, a division of Danone, needed to increase dough mixing capacity at their biscuit plant near Barcelona in Spain, they chose a Baker Perkins 850HS, equipped with the new option of Variable Frequency Drive (VFD). This allows the mixer to be run at any speed within its operating range, rather than just high and low speed.
The Lu mixing room supplies several production lines, and three high-speed 850HS batch mixers have operated successfully there for a number of years. The new machine mixes dough for hard-sweet sandwich biscuits, one of a wide range of brands made by Lu for the Spanish market.
The VFD option provides several advantages over the conventional two-speed mixer that have the potential to improve product consistency and operational efficiency. The ability to select mixing speed at will means that a mixing profile can be developed to match the characteristics of each type of dough. This is a level of control not available on mixers with two-speed motors. The single-speed VFD motor is also less expensive than the two-speed alternative.
Existing machines can benefit from this new technology via a retrofitted VFD package.
Profiles can be developed that base the mixing cycle on energy input, final mixing torque, and time, or a combination of all three. This can give higher levels of consistency, verified via log traces, and can also significantly reduce energy costs.
The Variable Frequency Drive provides improved working conditions, with less noise and vibration as the machine starts up and changes speed; this also impacts on maintenance requirements. An additional maintenance benefit is the use of an 'off-the-shelf' motor rather than the bespoke unit required for two-speed mixers.
A further benefit is the elimination of the power surge that can occur when a two-speed mixer is started or changes speed. This can cause a drop in factory voltage, and reduced torque on the mixer motor that may lead to stalling.
Baker Perkins has supplied several hundred High Speed mixers to biscuit factories world-wide. These multi-purpose machines are available in batch sizes from 550 to 1100kg, and are suitable for hard and soft biscuit doughs, and snack doughs.
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