§ 1036.527 - Powertrain system rated power determination.

§ 1036.527 Powertrain system rated power determination.

This section describes how to determine the peak and continuous rated power of conventional and hybrid powertrain systems and the vehicle speed for carrying out testing according to §§ 1036.505 and 1036.510 and 40 CFR 1037.550.

(a) Set up the powertrain according to 40 CFR 1037.550, but use the vehicle parameters in § 1036.505(b)(2), except replace P_contrated with the manufacturer declared system peak power and use applicable automatic transmission for the engine. Note that if you repeat the system rated power determination as described in paragraph (f)(4) of this section, use the measured system peak power in place of P_contrated.

(b) Prior to the start of each test interval verify the following:

(1) The state-of-charge of the rechargeable energy storage system (RESS) is ≥90% of the operating range between the minimum and maximum RESS energy levels specified by the manufacturer.

(2) The conditions of all hybrid system components are within their normal operating range as declared by the manufacturer.

(3) RESS restrictions (e.g., power limiting, thermal limits, etc.) are not active.

(c) Carry out the test as follows:

(1) Warm up the powertrain by operating it. We recommend operating the powertrain at any vehicle speed and road grade that achieves approximately 75% of its expected maximum power. Continue the warm-up until the engine coolant, block, or head absolute temperature is within ±2% of its mean value for at least 2 min or until the engine thermostat controls engine temperature.

(2) Start the test by keying on the powertrain and letting it sit at 0 mi/hr for 50 seconds.

(3) Set maximum driver demand for a full load acceleration at 6% road grade starting at an initial vehicle speed of 0 mi/hr.

(4) 268 seconds after the initiation of paragraph (c)(3) of this section, linearly ramp the grade from 6% to 0% over 300 seconds. Stop the test after the vehicle speed has stopped increasing above the maximum value observed during the test.

(d) Record the powertrain system angular speed and torque values measured at the dynamometer at 100 Hz and use these in conjunction with the vehicle model to calculate P_sys,vehicle.

(e) Calculate the system power, P_sys, for each data point as follows:

(1) For testing with the speed and torque measurements at the transmission input shaft, P_sys is equal to the calculated vehicle system peak power, P_sys,vehicle, determined in paragraphs (c) through (d) of this section.

(2) For testing with the speed and torque measurements at the axle input shaft or the wheel hubs, determine P_sys using the following equation:

Where:

P_sys,vehicle = the calculated vehicle system peak power.

ε_trans = the default transmission efficiency = 0.95.

ε_axle = the default axle efficiency. Set this value = 1 for speed and torque measurement at the axle input shaft or = 0.955 at the wheel hubs.

Example:

P_sys,vehicle = 317.6 kW

(f) The system peak rated power, P_rated, is the highest calculated P_sys where the coefficient of variation (COV) <2%. The COV is determined as follows:

(1) Calculate the standard deviation, σ(t).

Where:

N = the number of measurement intervals = 20.

P_sysi = the N samples in the 100 Hz signal previously used to calculate the respective P_µ(t) values at the time step t.

P̄_µ(t) = the power vector from the results of each test run that is determined by a moving averaging of 20 consecutive samples of Psys in the 100 Hz that converts P_µ(t) to a 5 Hz signal.

(2) The resulting 5 Hz power and covariance signals are used to determine system rated power.

(3) The coefficient of variation COV(t) shall be calculated as the ratio of the standard deviation, σ(t), to the mean value of power, P̄_µ(t), for each time step t.

(4) If the determined system peak rated power is not within ±3% of the system peak rated power as declared by the manufacturer, you must repeat the procedure in paragraphs (a) through (f)(3) of this section using the measured system peak rated power determined in paragraph (f) of this section instead of the manufacturer declared value. The result from this repeat is the final determined system peak rated power.

(5) If the determined system peak rated power is within ±3% of the system peak rated power as declared by the manufacturer, the declared system peak rated power shall be used.

(g) Determine continuous rated power as follows:

(1) For conventional powertrains, P_contrated equals P_rated.

(2) For hybrid powertrains, continuous rated power, P_contrated, is the maximum measured power from the data collected in paragraph (c)(3) of this section that meets the requirements in paragraph (f) of this section.

(h) Vehicle C speed, ν_refC, is determined as follows:

(1) For powertrains where P_sys is greater than 0.98 · P_contrated in top gear at more than one vehicle speed, ν_refC is the average of the minimum and maximum vehicle speeds from the data collected in paragraph (c)(4) of this section that meets the requirements in paragraph (f) of this section.

(2) For powertrains where P_sys is not greater than 0.98 · P_contrated in top gear at more than one vehicle speed, ν_refC is the maximum vehicle speed from the data collected in paragraph (c)(4) of this section that meets the requirements in paragraph (f) of this section where P_sys is great than 0.98 · P_contrated.

[86 FR 34386, June 29, 2021]