The Real Power
Power semiconductor devices in the inverter directly interface to the permanent magnet, inductive, or other motors in an EV or HEV. The inverter takes the dc energy in the battery and converts it to the ac power required to run the motors.
“Getting the inverter to be more efficient has a direct impact on the battery size,” said Carl Bonfiglio, segment marketing manager for hybrid and electric vehicle technologies at Infineon Technologies, North America.
Bonfiglio has observed that carmakers’ requests for higher power levels have reached a plateau. “We don’t see that they are going to be increasing the amount of power they want out of an inverter, so the push is on to shrink the inverter,” he said.
In his presentation at the SAE 2011 Hybrid Vehicle Symposium & EV Symposium in Anaheim, California, Jochen Hanebeck, president of Infineon‘s Automotive Division, discussed many changes that can be expected in power semiconductor technologies for future EVs and hybrids.
Compared to today’s standard technology, with 200°C junction temperature operation, Hanebeck said it’s possible to achieve more than 60% higher output power per unit silicon area at the same lifetime and more than 500% larger lifetime per unit silicon area at the same output power. Another alternative is more than a 40% reduction in silicon area at the same lifetime and output power with higher temperature coolant capability to eliminate the low temperature radiator (Fig. 5).
Gate driver IC improvements can have a huge benefit on the system. Being able to quickly diagnose different fault conditions and then take action and communicate with the main microcontroller so it can respond appropriately is occurring now. “The industry as a whole used gate drivers that were developed for industrial motor control where diagnostic requirements aren’t so high,” said Bonfiglio.
On-board diagnostics (OBD) requirements alone are sufficient to drive these improvements. With the revisions, the current approach can be optimized for lower cost and reduced system complexity.
TT electronics developed the custom micro-inverter/modules for Protean Electric’s IWM. Steve Jones, director of Global Technology at TT electronics, sees significant advantages for integrated in-wheel electronic drive systems that include providing sufficient power and torque for larger SUVs and saving packaging space in the vehicle. He has also been involved with alternate motor and semiconductor technologies.
“We’ve seen some interest in inductive control with hybrids, where the car is driven electrically within a city and with an internal combustion engine elsewhere,” said Jones. “This is a modification that can be done quickly with a short time-to-market.”
TT electronics has implemented several technologies in its development of new products for the EV/HEV market. “The use of SiC devices and compatible packaging provide application advantages including greater power density, lower switching losses, higher operating frequencies, and higher operating temperature,” said Jones.
Alternate motor technologies and advanced semiconductor devices certainly aren’t the only potential changes for powering future EVs and HEVs. According to Dave Torrey, vice president of engineering at Ioxus Inc., motor drives are one of the vehicle systems that can benefit from ultracapacitors, which can supplement the battery voltage under acceleration conditions.
“If you had an ultracapacitor, you really have an energy system that is hybridized between batteries and ultracapacitors,” said Torrey. “And the ultracapacitors could support that power.”
The Right Direction
Carmakers are moving toward lower fuel consumption, greater electric driving range, and longer time between charges. To head in that direction, they need help from a range of suppliers with enabling technologies. Any trip begins with the first step.
“I still see the whole hybrid market really in the infancy stage,” said Ansys’ Stanton. “To me it seems like the wild west of the automotive industry 100 years ago. You have all these small suppliers and OEMs, guys in garages coming up with motors and designs that they are trying to sell to the automotive industry.”