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Product category: Industrial Drives/Controls
News Release from: Mitsubishi Electric Automation Systems | Subject: F740 variable speed drive
Edited by the Engineeringtalk Editorial Team on 27 February 2008

Variable speed drive keeps potatoes
preserved

The F740 variable speed drive helps match fan speeds to the conditions experienced by the potatoes, keeping them preserved at a lower cost.

Today's supermarket shoppers may be surprised to hear that potatoes are a seasonal vegetable; they appear all year-round in every store Their parents though are likely to remember that potatoes where harvested in autumn, stored in outside clamps for perhaps six months, after which they were likely to be sprouting in all directions, ugly and hard work to prepare for cooking

These days potatoes are stored in climatically controlled buildings in a state of virtual suspended animation so that they retain the 'just out of the ground' appearance and taste so vital to modern consumer marketing.

Crop Systems Technical Consultant Ray Andrews, said: "A typical bulk potato store may hold between 500 and 3000 tonnes of potatoes with the more modern unit being 30 by 30 by 7m.

It will be totally insulated and have a large fan house at one end".

The objective is to maintain optimum storage conditions by controlling the temperature, humidity and CO2 content of the atmosphere.

Until recently the philosophy was to have large, fixed speed fans running flat out, regardless of conditions, a setup which made it impossible to truly optimise conditions.

"We have developed the Evolution controller to give many varying levels of control through different types of sensors located around the store, from this we can adjust the fan speed according to the exact requirements", says Andrews.

In fact, when newly harvested potatoes are put into storage, their surface moisture content is high and over the first few weeks this moisture needs to be removed relatively quickly.

The system is designed with an automatic load cure program, this keep the fans running at an economical speed until the stock has settled down.

The potatoes also emit heat, which if left build up would compromise storage.

The fans adapt their speed to compensate for different conditions.

"We have also developed a automatic fogging program so that we can better address the distribution of CIPC fog within the storage area and we have proven that 'stirring' and re-circulating the air at reduced air speeds helps give far better efficacy and extends the fogging intervals dramatically, this speeds the payback period to less than 18 months in some cases".

Central to the storage processes above is the use of an F740 variable speed drive from Mitsubishi.

The F740 is the fan rated version of the F700 range of drives and offers improved motor efficiency during constant speed operation and acceleration periods and optimum torque patterns which accurately match the power delivered to that required at any instant.

Optimisation is effectively instantaneous, so the drive is always giving maximum performance and efficiency to the load.

Its ease of commissioning, its removable terminal block, on-board EMC filter, predictive maintenance monitor and tripless reliability, as well as its ability to optimise energy usage, made the F740 suitable for this fan drive application. Request a free brochure from Mitsubishi Electric Automation Systems ...

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