broadbent spins energy savings with vacon drives
TRANSCRIPT
broadbent spins energy savings with vacon drives
Reference Story
Thomas Broadbent & Sons, the UK’s preeminent developer
and supplier of solid-liquid separation equipment, is now
using Vacon AC variable speed drives with Active Front End
(AFE) technology to recover up to 90% of the energy con-
sumed by the batch centrifugals it supplies to the sugar pro-
cessing industry.
The centrifugals are designed for processing massecuite, a
mixture of sugar crystals and molasses, which is produced by
the crystallisation phase of sugar refi ning. The centrifugals
spin the massecuite in a perforated basket, which typically
has a diameter between 1.2 m and 1.8 m, at speeds of up to
1,200 rpm. The liquid molasses is forced through the perfora-
tions, leaving behind sugar crystals that are ready to be sent
to a granulator for drying.
The batch centrifugals produced by Broadbent work with
loads of between 1.5 and 2 tonnes, and can process up to 25
loads per hour. The centrifugals are driven by AC motors rat-
ed between 160 and 400 kW, depending on the capacity of the
machine. Because the operating duty is so onerous, standard
motors are not ideal for this application, so Broadbent pro-
duces special motors of its own design.
Fitted with a non-regenerative drive, the centrifugals would
have a very high-energy consumption and, in addition, during
braking they would produce a lot of energy that would have
to be dissipated as heat. For this reason, Broadbent adopted
regenerative drives for its machines as soon as these became
readily available. These drives allow the energy produced
during braking to be fed back into the supply system, which
means that the net energy consumption of the centrifugals is
reduced by 80% or more. The problem of heat dissipation is
also eliminated.
The Broadbent engineers, however, constantly evaluate new
technologies as they become available to determine whether
they might offer benefi ts to the users of the company’s ma-
chines. As part of this process, they investigated the use of
Active Front End (AFE) drives. These are regenerative drives
of a special type that incorporate controllable solid-state
switches in their input section.
“AFE drives provide high effi ciency when operating in both
motoring and regenerative modes, and they also generate a
much lower level of harmonics than conventional regenera-
tive drives,” said Graham Hindle, Chief Electrical Engineer of
Thomas Broadbent & Sons. “We have, however, found that not
all drives of this type work well with our higher torque mo-
tors.”
Dependable and cost-effective Vacon Active Font-End
drives meeting customer needs
“We were, therefore, happy to accept when Vacon offered to
supply us with one of its AFE drives for evaluation. Our tests
showed that the Vacon drive could readily be tuned to meet
our needs and also that it offered better performance than
Vacon Drives UK Ltd.
18 Maizefi eld,
Hinckley Fields Industrial Estate Hinckley
Leicestershire, LE10 1YF, UK
Tel. +44 (0)1455 611 515
Fax. +44 (0)1455 611 517
E-mail: [email protected]
Web: http://www.vacon.co.uk RS
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other drives we had tested. And there was another important
benefi t – the Vacon drives was very competitively priced!”
Since selecting the Vacon AFE drives as the preferred op-
tion for its batch centrifugals, Broadbent has discovered that
they offer another signifi cant advantage. They are well suited
for use in applications where unpredictable interruptions to
the supply are likely to occur, which is a common problem in
some of the overseas locations where sugar cane is grown
and processed.
With conventional regenerative drives, loss of supply while
the centrifugal is braking frequently leads to failure of the
main fuses in the drive system. Not only is this a major incon-
venience, the fuses are also special semiconductor protec-
tion types that are expensive to replace. With the Vacon AFE
drives, however, this problem does not occur.
“We’ve now been using Vacon AFE drives for around fi ve years
and as well as offering consistently excellent performance,
they’ve also proved to be exceptionally reliable,” said Graham
Hindle. “We now fi t them to our batch centrifugals unless, of
course, the end user expresses a preference for drives from
an alternative manufacturer.”
Very good support
“We get very good support from Vacon, with prompt deliver-
ies and easy access to expert technical advice and guidance
although, in truth, we have rarely needed this. I suspect that
Vacon’s repair service is just as good, but the reliability of the
drives is such that we really haven’t had enough experience
of it to comment!”
For Thomas Broadbent & Sons, Vacon AFE drives are provid-
ing major benefi ts and these same benefi ts can be enjoyed in
many other applications. In fact, wherever dependable cost-
effective drives that support regeneration and generate low
levels of harmonics are required, the Vacon AFE units are an
ideal choice.