(R) Performance Characterization of Electrified Powertrain Motor-Drive Subsystem
|Publication Date:||1 February 2018|
This document was developed to provide a method of obtaining repeatable measurements that accurately reflects the performance of a propulsion electric drive subsystem, whose output is used in an electrified vehicle regardless of complexity or number of energy sources. The purpose is to provide a familiar and easy-to-understand performance rating. Whenever there is an opportunity for interpretation of the document, a good faith effort shall be made to obtain the typical in-service performance and characteristics and avoid finding the best possible performance under the best possible conditions. Intentional biasing of operating parameters or assembly tolerances to optimize performance for this test shall not be considered valid results in the scope of this document.
Background and Purpose
Electrified vehicles are increasing in market share, and are expected to continue to do so. These advanced vehicles are currently found on dealer lots and in marketing material. They are being compared to conventional vehicles powered by internal combustion engines; whether in light-duty, heavy-duty, or off-road applications. Additionally, these vehicles are being compared with other electrified vehicles which may operate with different voltage levels or powertrain configurations.
Currently there is no widely accepted standard for specifying the performance of a traction motor. It is our intention to be as similar in approach as possible to the existing worldwide standard UN ECE R85 (uniform provisions concerning the approval of internal combustion engines or electric drive trains intended for the propulsion of motor vehicles of categories M and N with regard to the measurement of net power and the maximum 30 minutes power of electric drive trains). In addition, a wide variety of powertrain configurations, as well as limitations arising due to the traction battery, cooling system, or vehicle controls, makes it difficult to predict the net and continuous power of the electric motor, the major component in an electric traction drive subsystem (ETDS), once installed in its application vehicle. The SAE J2907 test procedure provides an accurate assessment of the ETDS performance, under controlled laboratory conditions, using manufacturer supplied equipment settings, as the basis for in-vehicle performance as outlined in SAE J2908.
The test procedure, Section 4, is comprised of three sections:
An initialization procedure that includes specific preconditioning of the ETDS.
The maximum net power (synonymous with peak power) rating of the ETDS for manufacturer (MFG) specified power supply voltage, test speed, coolant system setpoints, and operator interface software.
The maximum 30 minute power rating, a measure of continuous power capability of the ETDS under manufacturer prescribed power supply voltage, test speed, coolant system setpoints, and operator interface software.
The tests detailed herein are application 'agnostic' and should not be interpreted as favoring any particular motor or inverter technology, powertrain architecture, or type of control employed. This recommended practice has been developed to document the consensus from industry stakeholders on acceptable motor test methods that enable a formal means of characterizing the motor as an ETDS component and communicating those characteristics. As such, the full ETDS represents the minimum hardware complement of this procedure, performed out of vehicle on a laboratory dynamometer using a regulated power supply. Use of high power industrial ac drive inverters and controls other than manufacturer supplied production algorithms (not to be modified) is outside the scope and purpose of this document.
Due to the inclusion of the inverter and associated production software, the majority of the testing results will reflect the characteristics of the motor in a specific application. The implementation of one motor design in multiple applications or with different inverters or with different algorithms and/or parameterization would require retesting to obtain the motor characteristics that represent the different motor drive systems. The procedures stated in this document apply whether the ETDS provides direct access to its motor shaft, or access via an integrated gearbox, so that test fixturing requirements are minimized.
This document should be viewed as a starting point for the standardization of electric traction motor testing. This technology will be evolving as newer and more integrated drive systems become commercially available. It is likely, therefore, that these test protocols will need to be periodically revisited and revised, as the technology matures.
Field of Application
The electric drive system in the scope of this document includes the ETDS consisting of:
• Drive motor with access to its output shaft, either directly or via a gearbox.
• Power inverter plus control electronics having MFG supplied production software.
• Cables and sensors as needed for operation, data acquisition, and operator interface software.
• Any enclosures required to support the operating system.
• Entire cooling system that mocks up vehicle usage.
This document is meant to cover electrified powertrain motor-drive subsystem regardless of end use. Typical applications include fuel cell EV (FCEV), battery electric vehicle (BEV), hybrid EV (HEV), plug-in EV (PHEV), or range extended EV (EREV), regardless of architecture.
Also included within this field of application are ETDS units as may be found in electric motorcycles, scooters, and low speed electric vehicles such as Neighborhood EVs.
Motor only characterization tests are not covered by this document. Instead, appropriate motor test procedures for the characterization of particular electric machine types, such as those illustrated in Figure 1 is described in the following IEEE Standards, and should be consulted for more in-depth testing.
• Std. 11 for rail and road vehicles
• Draft Std. P1812 for permanent magnet machines
• Std. 112 for polyphase induction motors and generators
• Std. 115 for synchronous machines
Appendices are provided in this recommended practice for recording pertinent information about the traction motor and its drive system undergoing test. Users are provided Appendix B as a template for recording results and Appendix A as a communications tear-off sheet that summarizes how well maximum (net) power and maximum 30 minute power match manufacturer declared values.