• • • TEST & MEASUREMENT • • •
HYBRID AND ELECTRICAL VEHICLE POWERTRAIN TESTING
By Randal Beattie, SAKOR Technologies
AC power with a large amount of harmonic content. These test systems tend to be rather complex and are usually the most sophisticated, with many elements to be tested and coordinated.
In-process and end-of-line testing - manufacturers verify performance and safety
Manufacturing end-of-line testing is usually performed to verify that no defects were introduced in the manufacturing process, and that the components will perform to specifications. Typical tests include operational validation, quick performance testing, as well as rigorous testing to validate that high-voltage electrical systems are properly isolated, and are therefore safe to use in vehicles. In-process testing may also be conducted to test
partial assemblies along the production line. This improves manufacturing efficiency and significantly reduces the chance that faulty components will find their way into the finished product.
O
ver the past decade, most transportation markets, from automotive, to military, aircraft, and even space systems have seen a tremendous surge of interest in hybrid and electric vehicle technology. To gain the promised efficiency benefits and green profile of these vehicles, it is important to conduct driveline and component testing during design and manufacturing that is specially adapted to the particular nature of hybrid and electric vehicles. Hybrid and electric drivetrains have several
features that make testing them very different from the standard testing conducted on internal combustion (IC) only systems. Hybrid and electric systems use regenerative braking (where braking actually generates power that is returned to and stored in the vehicle’s battery for later use). This typically requires addition of fairly complex AC inverter technology, and often more complex transmissions. In addition, these vehicles often have several
module control units (MCU’s), essentially small onboard computers, which control the functions of such major subsystems as the engine, transmission, and charging system, among others. To properly test these components, the test system needs to be able to communicate with one or more of these units via a high speed in-vehicle networks. This changing technology
and increased complexity requires a testing system very different, and more complex, than those used in IC-only systems.
The technology is out there to ensure proper testing and realization of the energy efficiency benefits promised by hybrid and electric vehicles. What’s more, the testing technology is itself energy efficient, reducing operations and maintenance costs and contributing to the vehicle’s overall environmental performance.
TYPES OF HYBRID/EV DRIVELINE TESTING
Hybrid or electric driveline testing is conducted at several stages during the development of a vehicle, and each has an important role to play.
Engineering testing - design engineers need precise measurements
Accurate measurements are critical so design engineers can extract every bit of efficiency from their designs. Otherwise they will lose much of the advantage of using hybrid/electric technology. Most vehicles use 3-phase AC motors driven by inverter technology, so sophisticated power analyzers are needed to properly measure 3-phase
38 ELECTRICAL ENGINEERING • DECEMBER/JANUARY 2021
Quality control testing - motor users look for defects in incoming product
Quality control (QC) testing is usually done on a percentage of the components to verify that that they perform over the specified range, and are relatively free of defects. For example, a fork lift company may conduct QC testing on a shipment of imported electric motors that are scheduled to be placed inside their forklifts. They would use QC testing to verify that the shipment coming from their supplier performs as specified and will not experience high failure rates in the field. This type of test system is typically less complex, because it does not have to measure as many items, nor to the degree of accuracy, as those tested in engineering systems.
REGENERATIVE BRAKING IS THE BASIS OF IMPROVEMENT IN FUEL ECONOMY
Hybrid or electric vehicles use 4-quadrant motor/inverter technology to either assist the engine (hybrid) or as the prime mover (electric vehicle). Four quadrant means that the electric motor can control velocity or torque in either direction − the motor can accelerate, run, and decelerate forward or backward. During deceleration, the system uses regenerative braking, so the electric motor is used
electricalengineeringmagazine.co.uk
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