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No. 3 November/December 2010
DESIGN DATA
Dave’s DIARY
DRIVES
In this regular feature, Dave Baston, UK General Manager
for Control Techniques, looks at how modern drive and
motor technologies can improve your business. In this issue,
Dave insists that a proposed rating system for variable speed
drives (VSDs) must take a system-level view
For as long as I can remember, I’ve advocated the use of variable
speed drives (VSDs) to raise motor efficiency. They cost more upfront,
but ongoing energy savings will dwarf the initial investment.
Their benefits in pump and fan drives are already well known, and
the EC Energy Using Products (or Ecodesign) Directive has identified
VSDs as a desirable technology. The biggest potential for energy
being applications that move air or fluids at an adjustable rate, i.e.
fans and pumps.
An obvious next step is to introduce an efficiency grading scheme
for VSDs, as is already done for electric motors. The EC has issued a
mandate to CENELEC to develop a suitable technical standard.
Developing it will be a technical challenge, because it’s difficult to get
an accurate measure of VSD efficiency: mostly because it’s already so
high (97-98%), measuring the ratio between input and output power
stretches current instrumentation to the limit. And that’s before we’ve
addressed more general questions: which operating conditions should
be covered? And how should results be weighted?
The key problem is that the quality of the drives output waveform
significantly impacts on the losses within the motor. The loss in a
VSD is 2-3% of rated throughput. The loss in the motor is 5-20%,
depending on the rating. A simple drive only efficiency rating would
be meaningless because it would ignore these system-level effects.
Any new standard for VSD efficiency must address this dilemma –
perhaps by defining an efficiency test between power source and
shaft, using a hypothetical ‘standard motor’. I can already hear the
arguments, but they’re worth overcoming if we’re to avoid a
simplistic standard for VSDs that ignores their effect on the motor.
Jargon Buster - The Ecodesign Directive
The Ecodesign Directive (http://ec.europa.eu/enterprise/policies/
sustainable-business/documents/eco-design/framework-directive/
index_en.htm) provides consistent EU-wide rules for improving the
environmental performance of energy related products (ERPs) through
ecodesign - a way of thinking about design which takes into account the
environmental impact of a product or packaging across its entire
existence, including Raw Materials, Manufacture, Retail, Use & End of
Life. This approach is known as life cycle thinking and can be used to
reduce environmental impacts as well as costs for businesses.
Do you agree? Tell us what you think:
Visit www.controltechniques.com/viewpoint
Rockwell Automation has published a White Paper
explaining how intelligent motor control centres
(MCCs) – which integrate communications,
hardware and software – can help to minimise
downtime. The eight-page publication outlines the
evolution of MCCs, configuration methods,
networking advantages, and real-world
application examples. It describes the underlying technologies,
including advanced monitoring and sensing devices, and network
connections. Intelligent MCCs can cost less to install than
traditional MCCs and offer protective, monitoring and
troubleshooting advantages. They also allow manufacturers to
capture and use equipment and process data to improve
productivity.
http://goo.gl/prgn
US-based Abhisam Software has announced the publication of a
downloadable eBook called The Quick Guide to AC Variable
Frequency Drives, which explains how drives work, and how to
select, use and install them in common applications. The
“vendor-neutral” guide contains six chapters covering all aspects
of VSDs from basic concepts related to AC induction motors and
their control, to an explanation of functions such as vector
control, torque control, anti-windmill control, and dynamic
braking. The eBook is available at an introductory price of $27,
and a free trial can be downloaded from Abhisam’s Web site.
www.abhisam.com
PI (Physik Instrumente) has published a 400-page
catalogue covering its piezomechanical
components and motion systems, from simple,
direct actuators, to long-travel ceramic linear
motors and complex multi-axis flexure guided
nanopositioning stages. A separate section lists
control electronics. The catalogue includes a
tutorial on piezo design for positioning applications. It can be
downloaded as a PDF.
www.piezo.ws/pdf/Piezo_Mechanism_Cat10.pdf
Thomson has produced a guide to using electric
linear actuators to replace hydraulic and
pneumatic cylinders in off-road machinery and
vehicles. Potential applications include controlling
engine speed, operating safety locks remotely,
lifting access panels, and controlling spool valves.
The publication compares electric actuators with
fluid power drives and outlines their advantages
including low development costs, easy installation, user-friendly
control functions, low energy costs, high adjustment accuracy,
low maintenance, and environmental acceptability. The brochure
is available as a downloadable PDF.
http://goo.gl/JJquQ
Leuze electronic has issued a 12-page brochure
describing its machine safety inspection service,
as well as its machine safety devices and support
services. It explains the company’s UK-based
technical support service, its 24-hour telephone
helpline, its parts return process, its machine
stop-time measurement service, and its machine
safety training. The publication also covers the free-to-download
ePlan macros for Leuze’s machine safety components
01480 408 500 mail@leuze.co.uk
http://bit.ly/LeuzeMachineSafetyInspections
48 November/December 2010 www.drives.co.uk