Electrical system helps handle frozen foods

Edited by the Engineeringtalk editorial team Jan 17, 2008

In order to prevent tripping, Block UK recommended adding a motor reactor (choke) that would smooth out the PWM (pulse width modulated) waveform.

Block UK and systems integrator MLH Services are helping two producers of ready meals minimise production downtime on their spiral freezer conveying process, using a range of panel-installed electrical components, including three-phase power supplies, EMC filters, inverter drives and motor reactors (chokes).

The control panels were built and installed by Peterborough-based systems integrator MLH Services.

The first control panel was installed at Headland Foods' production plant in Flint, North Wales, in order to control the spiral freezer process and associated cooling fans.

The Headland Foods plant at Flint uses a spiral freezer system, custom-designed and installed by KE Parafreeze (formerly KE Jackstone), a Norwich-based company that specialises in the design and manufacture of industrial freezers.

David Everington, Director of KE Parafreeze said: "The function of the spiral freezer system at Headland Foods is to freeze a high throughput of ready meals that pass through the plant, before they are shipped off to customers".

"The spiral freezer is fed by a conveyor system".

"The ready meals move slowly around the spiral-shaped freezer system, for around 45 minutes in total, after which they are sufficiently frozen to be ready to be shipped to customers".

"As a company, we designed and manufactured the freezer system, but for the associated electrical control panels, we used MLH Services, a local company with considerable expertise in small OEM and industrial automation systems".

The novel design of the spiral freezer minimises the production space required in the factory and also ensures that the plant can meet high production volumes.

The system is therefore critical to Headland Foods' production process and so downtime must be kept to a minimum.

Back in 2002, after installing the spiral freezer system, associated cooling fans and control panel, there were some initial teething problems.

Fan overload switches tripped occasionally, causing production downtime.

The 12 cooling fans that blow cold air through the spiral freezer were controlled by a single inverter drive via 12 separate thermal overloads.

After consultation with Block UK, MLH Services concluded that the overloads were being tripped by reflective wave transience due to a long total cable length from the inverter to the 12 cooling fans.

In order to prevent tripping, Block UK recommended adding a motor reactor (choke) that would smooth out the PWM (pulse width modulated) waveform, closer to a sinusoidal waveform, thus improving the power quality.

Mark Langfield-Holland, Partner at MLH Services comments: "With help from Block UK, we were able to quickly select and source an appropriate motor choke, which we duly installed in the control panel".

"This helped smooth out these irregular waveforms".

"Since installing the motor choke, there have been no further problems with the fan overloads".

After the successful installation at Flint, KE Parafreeze and MLH Services have completed a similar system for Cascade Marine, a producer of ready meals based in Dubai.

This time, the panel was skid-mounted so that the customer could install the system as a complete freezer unit.

Another identical control panel for a second spiral freezer system is also currently being installed at Cascade Marine.

Again, Block UK supplied the three-phase power supplies, EMC filters and motor chokes for the control panels.