Shooting for the Electric Land Speed Record—with Off-the-Shelf Motors
Power and automation technology supplier ABB could be taking its place in the record books in early June this year, when its drives and motors equipment will be used to power the British challenger to the world electric-land-speed record. The attempt is scheduled to begin on June 9 on the Chott-el-Jerid salt flats in Tunisia.
An ABB industrial drive and two 50-hp AC motors will be used to drive the ABB e=motion electric car to speeds in excess of the current world record of 245.523 mph held by the White Lightning team from the United States. Based on the development and testing data, the car could also set another first-it might become the first-ever electrically powered vehicle to break the 300 mph barrier.
Already gone 146 mph
With its motors producing a combined output of more than 500 bhp (the horsepower produced at the motor shaft), ABB's system has already helped propel the e=motion car to 146 mph during testing, unofficially breaking the 139 mph U.K. electric record, and equaling the first-ever land-speed record set by Sir Malcolm Campbell's petrol-driven car in 1924.
When they were building the car, its designers, Mark Newby and Colin Fallows, set a goal of using only equipment that could be sourced easily off-the-shelf from any supplier, both to reduce the cost of the project and to add to the prestige of the challenge. The system uses a standard inverter from ABB's ACS800 motor drives line to convert the 600-volt DC output from the car's four packs of lead-acid batteries into AC power for the two motors; the motors are a type commonly used in machine tool and a host of other applications.
To qualify as an official world record under FIA rules, the car must perform two recorded runs at better than 252 mph over a distance of one kilometer (0.622 mile), requiring the motors to reach speeds in excess of 6,000 rpm.
To put this in perspective, in ordinary use the motors would normally run at between 1,000 and 3,000 rpm. So, to prevent overheating during the world-record attempt, each motor has been adapted with a forced-ventilation system that's comprised of a 24-volt DC fan, to help keep the motors within their maximum operating temperature of 356run during the record attempt.
Immediate, high torque is critical
A major consideration in the drive system design was the car's ability to accelerate quickly to achieve maximum speed within the permitted distance. For this reason, the drive system features ABB's DTC (direct torque control) drive technology, which provides control of motor torque, with full motor torque available, even at zero speed.
"Other challengers to the record commonly use gear-driven systems in their cars to achieve the fastest possible acceleration, whereas the technology we've supplied steadily controls torque across the whole speed range," says Frank Griffith, a member of the ABB team that helped to develop the car's power system. "Although a geared vehicle can achieve 100 mph in a few seconds, its rate of acceleration falls away much more quickly compared to our system; this one will continue to accelerate even past the 300 mph mark, provided sufficient battery power is available," he explains.
The system's ability was proven during the car's first test run at the Bruntingthorpe airfield in Leicestershire, U.K., in the summer of 2003, when the car unofficially beat the existing British electric-land-speed record within one-third of the distance traveled by the current official title holder.
"The car used by the Bluebird team, which holds the current British electric-land-speed record, reached a top speed of 139 mph over a distance of two miles. In its first-ever test run, ABB e=motion easily reached 146 mph within just over 900 meters (1,000 yards). In fact, the only reason we had to stop the car was because we ran out of road!" says Newby. "With this sort of performance, we're convinced that our car can beat easily the existing world electric-land- speed record."
For Newby and Fallows, finding a company that could supply the equipment needed to power the car proved a frustrating struggle that would last 18 months. "Of the companies we originally approached, none could provide either the technology or expertise that justified a world- record attempt of this magnitude," says Newby. "In fact, one suggested a water-cooled drive solution which resulted in us extending the nose of the vehicle by some 1.5 meters at great expense."
The search for a supplier ended in November 2002, when they approached ABB and found that the company was able to provide a solution. "Its solution proved extremely compact and means our car does not even need to be the 10 meters that it is!" says Fallows.
Along with Frank Griffith, the drive system developed for the ABB e=motion car is the work of team members Steve Malpass and John Schofield. One of the biggest challenges for the team was the need to simulate likely vehicle dynamics and performance before the car had even run.
Griffith explains that likely performance was modeled and calculated using a set of estimated conditions involving factors such as rolling resistance, drag and battery discharge rate. But much of this information either did not exist. "Or else [it] had to be extrapolated from data found on the Internet," says Griffith, "such as when we were trying to obtain figures for potential tire resistance at 300 mph. Not only that, but we only had a limited amount of space available for installing our system in the car, so we had to ensure that whatever we came up with was also compact."
To help fine-tune the system's performance, ABB used data from the two independent four-channel data loggers incorporated within the drive. During testing performed at the Bruntingthorpe airstrip, the data loggers were used to collect a range of data on drive and motor status, which was uploaded to a PC for analysis using ABB's Drives Window tool.
"The data loggers enabled us to improve the performance of our system in the same way as Formula One teams do with their cars," explains Malpass. "One of the data loggers was set to a rapid sampling rate of one sample per millisecond to record all the actual events as they happened. By setting the other logger to a slower rate, we were able to record information on trends that occurred throughout the test runs, which provided us with an overall picture of how the car was faring."
Using the data loggers proved invaluable in helping to trace the cause of higher-than-expected torque, which occurred during several of the test runs at Bruntingthorpe. "The acceleration data collected during the test runs indicated much higher torque than we'd expected," explains Griffith. "After examining all of the mechanical and electrical factors, we were relieved to find that this was actually due to the track being on a two-inch incline, something which we hadn't noticed previously!"
Speed gains gallop
With several weeks still to go until their initial attempt, Newby and Fallows are already planning their next-to take their car even faster.
"Since 1972, the world electric-land-speed record has shot from 152 mph to the current official record of 248 mph, an increase of 96 mph," says Newby. "In this same period, the record for petrol fuel cars has only risen by 6 mph. There is obviously fantastic potential for electrically powered vehicles, and we aim to be the ones to set the limits to beat for future challengers."