New drive technologies, new safety requirements
Recent industry trends toward high-performance electric and hybrid vehicle (EHV) drives has created a new set of testing requirements. New systems call for onboard electrical energy stores and drive units with battery power requirements of up to 1,000V depending upon vehicle size and type. While such high-voltage systems are commonly known for their stationary use within power generation and energy distribution applications, they are still fairly unfamiliar to onboard EHV applications.
It is important to understand that, if EHV drive construction was the same as traditional 12-, 24- or 42-Volt (nominal) on-board systems, units would create unreasonably high power requirements and end user costs, directly affecting a manufacturer’s ability to produce cost-competitive new vehicles. Because power is a byproduct of both current and voltage, EHV on-board system voltage must increase to keep currents within “reasonable” limits. Such increased capabilities can diminish cable cross-sectioning requirements while fully optimizing drive system efficiency.
To ensure optimal EHV performance, numerous tests must be conducted during the new vehicle development process. Suitable mobile vehicle data acquisition systems are vital for ensuring system competency, functionality and efficiency. In addition, proper incorporation of this technology as a viable onboard power source within an operating EHV requires a commitment to stringent safety testing and risk-mitigating hardware and accessories.
A typical high-voltage onboard system
A typical high-voltage onboard system consists of two key components: The direct current grid (DC voltage) of the energy storage device; and the three-phase alternative current grid of the RPM-regulated drive (rotary current, 3-phase AC). An example of typical EHV high-voltage component positioning is shown below, as well as a typical block diagram of direct and alternating circuits found within these systems. Please note that universal safety precautions for AC and DC voltages must be followed at all times.
Common measurement parameters
Electrical drive energy balance is a key EHV drive system measurement parameter, and particularly, studies of