Electric motor stators on an assembly line at the GM Baltimore Operations. When finished, the 130-hp (130-kW) motors will be used in the Chevy Spark EV.
Compared with the Spark with its standard 84-hp, 1.2-liter gasoline engine, the Spark EV has a 130-hp electric motor. The EV is more aerodynamic than its kin, says Chuck Russell, Spark EV chief engineer, thanks to features including a closed front grille, aero shutters in the lower grille, different front and rear fascias, an underbody cover, added rocker cover, and a modified rear spoiler.
The stack of laminations for the rotors. Magnets are inserted into the slots on the top. Note just right of center how there is a discernible vertical line that is not straight. That is deliberate. It is designed to help shape the magnetic field created.
The drive unit for the Spark EV. The planetary gear set to the right of the motor is actually a part used for GM six-speed transmissions. This is one way that they’re able to keep costs down for the unit.
The GM Baltimore Operations (GMBO) facility is not an old plant. The 471,000-sq. ft. facility has been producing transmissions and torque converters for everything from the Chevy Silverado 2500/3500 full-sized pickups to the Corvette for more than a decade. Since start of production in December 2000, GMBO has produced 1,419,038 transmissions.
But an interesting thing happened a couple of years ago, when there was a ground breaking at the site in White Marsh, MD. Corporate, state, and local officials moved dirt for what has become an 110,500-sq. ft. building filled with a variety of equipment, from Fanuc robots (fanucrobotics.com) to Promess electromechanical servo presses (promessinc.com). The facility was set up to produce permanent-magnet electric motors (or, as Pete Savagian, GM, general director, electric drive systems engineering, says, “electric machines,” as this is the nomenclature that those in the field use) for the 2014 Chevrolet Spark EV. The motors (we admittedly aren’t in the field) produce 100 kW and 542 Nm . . . or 130 hp and 400 lb-ft of torque for the minicar that will initially be sold in California and Oregon, then make its way to markets including Canada, parts of Europe, and South Korea.
And before leaving South Korea, it is interesting to note that the Spark EV and the gasoline-powered version are built in the GM plant in Changwon, South Korea. The 560-lb. lithium-ion battery pack (consisting of 336 cells) for the electric vehicle (EV) is built in Livonia, MI, by A123 Systems. And the drive system (including the motor—which was developed in Pontiac, MI) is being produced in White Marsh. This is truly a global program.
And before leaving the overview of GMBO, it is worth noting that the women and men who work there (186 hourly, 64 salaried) are not wholly unfamiliar with advanced powertrain technology: the Hybrid Two-Mode transmission that is used in GM pickups and SUVs is produced at that plant, too.
Speaking of the Spark EV motor, Savagian says that its performance is comparable to those used for machine tools. Which leads to the question of why, then, is GM manufacturing these motors rather than sourcing them from companies that produce motors for machining centers and the rest?
And the answer is that what’s needed for EVs is different than the requirements for machine tools. For one thing, the EV motors must be quiet; there must be low vibrations. Clearly, this is not high on the checklist so far as factories are concerned. The EV motors provide safety-critical torque—when you’re zipping along in a Spark EV on the freeway, you don’t want to have your motor fail—so the levels of quality and reliability must be exceedingly high. This is not to say that quality and reliability aren’t important for the motors used for machining centers, but it is of a different nature. Savagian says the EV motor reliability and safety requirements are more analogous to elevator motors. Importantly, because this is the auto industry, affordability is essential.
This is not to say that GM is going to be the source of electric motors for all of its existing or future hybrids and EVs, be it for the Volt (which is similar to the Spark EV setup; according to Chuck Russell, Spark EV chief engineer, who also worked on the Volt, by taking advantage of learnings from the Volt—ranging from the battery to the HMI to the motor—“We were able to reduce the lead time on vehicle development”) or for the eAssist that is available in a variety of its models (though eAssist uses an induction motor, not a permanent-magnet type).
Larry Nitz, who heads up global electrification engineering for GM, says of their approach to motors, “We will build, we will buy, and we will partner where we see fit as part of our portfolio for electric vehicles.” He also points out that since 2003 the company has been creating an extensive capability when it comes to designing, developing, processing, and validating electric motors and batteries.
A key reason why they’re building the Spark EV motor at GMBO is because they want to have the necessary under-standing of what it takes to build a motor: When they go out to the supply base, they’re speaking from a position of first-hand understanding. As Savagian puts it, “There are subtleties we can only learn by doing.”
Speaking of first: GM is the first U.S. automaker to be producing motors for EVs.
While the number of motors that can be produced in the GMBO eMotor building is something that GM isn’t revealing because the number of Spark EVs is also being kept inside, the factory is setup with a sufficient amount of flexible automation supplemented by manual operations such that it seems that it would be fairly easy to ramp up to higher volumes. This is not a low-volume arrangement by any stretch of the imagination.
For example, the bending of the square copper wires that are used in the stator (128 wires) is performed in robot-based cells; there are nine different shapes produced (two of those shapes are welded together so that there are eight part numbers). The wires are manually inserted into stator stack. The ends of the wires are automatically welded. Varnish is robotically applied. The stator is manually bolted into the housing. The rare-earth magnets in the 10 silicon-iron laminate sections that are stacked to create the rotor core (400 magnets are used per motor) are manually positioned (as are the stacks, which are slightly offset for purposes of controlling what’s called “torque ripple”: Nitz explains that to minimize vibrations in the electric motor, the magnetic field has to be specifically tailored, so the stacks are built up such that they create a herringbone pattern on the OD and there are precise features stamped out of the laminates to control the flow of the magnetic field).
In mid-April 2013, when Governor Martin O’Malley comes to the plant for the official start of production ceremony for the motor (in full campaign mode he tells the assembled, “The only way to strengthen the red, white and blue for the future is green!”), the capacity of the plant is evident. “We’re early in the launch process,” plant manager Bill Tiger says. One gets the sense that they’re ready to go full-bore into the production process. Should the volumes of the Spark EV be high, the people at White Marsh are prepared.