Page 17 - Industrial Technology EXTRA 15th February 2021

suggest they’re completely unaffected. Quite simply,
electrical resistance is a function of temperature,
and therefore a warmer motor becomes less
efficient. This effect is compounded by an increase
in counter-electromotive force created by the more
resistive coils. High temperatures also decrease the
flux density of the magnets, even further reducing
efficiency.
These losses in efficiency can add up very
quickly, particularly when summed across
potentially hundreds of motors on a production line.

Peaks and valleys
Another impact of high temperatures on equipment
comes when the temperature drops. In bakeries this
exposes equipment to particularly high is often the case when ovens are left to cool for
temperatures. Humans can work in those cleaning or line maintenance. Equipment constantly
conditions, but it’s not particularly safe or exposed to high temperatures will cool as well, but
comfortable, so why not get technology to do it this is where the problems sneak in.
instead? On the face it seems like an obvious Again, it’s simple physics that causes the issues.
solution, but as with most things in engineering, Materials expand as they are heated, and as the
seemingly obvious fixes are never quite that simple. motor cools different parts of it, from the stainless
The first consideration is direct heat damage to enclosure to the permanent magnets, to the rotor
equipment. material to the copper windings, cool and contract
at different rates.
Don’t get burnt Over many heating and cooling cycles this effect
Most food-grade electric motors, for instance, are slowly walks components out of tolerance, step by
typically constructed from easily washable stainless step, until they’re unacceptably loose. This directly
steel, with magnets and copper windings. There decreases the lifespan of the motor through
may be hundreds or thousands of discrete motors increased wear and tear. But, in the context of food
on a bakery production line, and while there is not and beverage manufacturing with its stringent anti-
much to denature or melt inside them, that doesn’t contamination measures and deep-cleaning, high-
account for the supporting infrastructure. pressure spray washdowns, it also opens up
While this will be similarly externally food-safe, enclosures to ingress.
with paint-free surfaces and spray-washable There’s a surprising amount to consider when
stainless enclosures, the shielding for the wire, installing automation equipment where it’s exposed
connector inserts and other appended monitoring or to high temperatures. If tackled cleverly, with proper
control equipment can suffer under extreme monitoring infrastructure and modern maintenance
temperatures. techniques, bread can be provided without any
While motor meltdown is not a likely outcome of circus.
exposing motors to extreme heat, it’d be wrong to www.euautomation.com/uk/

February 2021 • INDUSTRIAL TECHNOLOGY EXTRA • p17