Feature 40 years of drives & motors
The future of drives and motors is closer than we think
Drives and motors have come a long way in their functionality since the 1970s, but even greater capabilities are just around the corner, says Steve Ruddell, head of global marketing – motors & generators, ABB
paper machines, making them more responsive to changes in speed. Subsequently ABB developed new algorithms for motor control, which are integrated in its direct torque control (DTC) launched in the late 1990s, which is still the benchmark for performance.
Looking forward
Motors and drives have come a long way in the past few decades, but what technologies are waiting in the wings to form the basis of the drives of the future?
The first practical flux vector
drive, launched by ABB in 1984
esign Solutions celebrates its 40th anniversary this year, and since its launch we have seen steady development in those workhorses of industry – motors and variable-speed drives (VSDs). Motors have been ubiquitous
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throughout industry for a long time, indeed the AC induction motor was developed by Nikola Tesla in 1883. Soon after the AC motor was devel- oped, engineers came up with methods of varying its speed, and at first the only practical way of doing this was to provide the motor with a variable frequency, by using a DC motor turning an AC alternator. This method was used on a wide range of applications from the 1950s through to the 1970s. An intermediate step was the static AC variable-speed drives of the current source design. Later, when pulse width modulation (PWM) drives became the norm, use of the six step variable frequency drive declined, except for unusual applications where the regener- ative capability was an advantage. The PWM AC drive has become the drive of choice for applications including those requiring high starting torques, high continuous torque at low speeds, or fast dynamic response.
The first digital drives were launched in the early 1980s. Based on micro- processors, they offered better reliabil- ity, reduced maintenance, and vastly
Design Solutions 1971-2011
improved diagnostics compared to the analogue drives that preceded them. While ‘electronic’ DC drives have always used thyristors, early AC drives also used thyristors for switching, each of which requires an auxiliary thyristor to switch it off. This made them large and heavy, and they took up a lot of space. This improved on thyristor switch- ing by using GTOs and power transis- tors, which were smaller and so made
One interesting possibility that holds out great potential for electrical supplies and electronics is carbon nanotubes. Also known as CNTs, these are tubes of carbon atoms with walls just one atom thick. This exotic material may not seem to have much use outside a laboratory, yet it is already in something very mun- dane that is familiar to all electrical engineers – electrical brushes for DC and slip ring AC motors.
These are a critical failure point – improving them could save thousands of pounds in maintenance. Stretched through the plastic matrix of the brush, CNTs improve electrical and thermal conductivity, allowing the
‘Motors and drives have come a long way in the past few decades, but what technologies are waiting in the wings to form the basis of the drives of the future?’
the drive itself much more compact. Today, these devices have given way in their turn to the IGBT.
The hardware of drives is, of course, only half the story, the other half being drive software. This has two functions: control of the inverter output and control of the user interface. Although AC vector technology was known as early as 1970, the first practical flux vector drive was launched by ABB in 1984. The advent of flux vector drives brought other benefits to the process engineer, namely closer tolerance on both speed and torque control. This was particu- larly useful for applications such as
- 40TH ANNIVERSARY SUPPLEMENT -
amount of carbon filler to be reduced from around 30% to nearer 4%. CNT brushes provide better lubrication and cooler running, as well as being less brittle, stronger and allowing more accurate moulding. With their great thermal conductiv-
ity, CNTs can act as very effective heat sinks, allowing a much higher density of electronic components. VSDs using these heat sinks could be smaller and lighter. So, who knows where we might see these smaller VSDs in future, perhaps electric cars, controlling each wheel individually to give ultimate traction control. Or how about electrically powered
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