Commission Implementing Decision (EU) 2019/314Show full title

4. METHOD 2 (‘COMBINED METHOD’) U.K.

4.1. Efficiency of the 48V motor generator plus the 48V/12V DC/DC converter U.K.

The efficiency of the 48V motor generator plus the 48V/12V DC/DC converter shall be determined in accordance with ISO 8854:2012, with the exception of the elements specified in this section.

Evidence shall be provided to the type approval authority that the speed ranges of the efficient 48V motor generator are consistent with those set out in Table 1.

The measurements shall be conducted at different operating points, as set out in Table 1. The efficient 48V motor generator plus the 48V/12V DC/DC converter current intensity shall be defined as half of the rated current of the 48V/12V DC/DC converter for all operating points.

The rated current of the 48V/12V DC/DC converter is defined as the output nominal power of the 48V/12V DC/DC converter divided by 14,3V. The nominal power of the 48V/12V DC/DC converter shall be the continuous output power at the 12V side guaranteed by the manufacturer of the DC/DC converter at the conditions specified in the ISO 8854:2012.

For each speed the voltage and the output current of the motor generator shall be kept constant, the voltage at 52 V.

The efficiency at each operating point shall be calculated in accordance with Formula 12:

Formula 12

All efficiency measurements are to be performed consecutively at least five (5) times. The average of the measurements at each operating point ( ) shall be calculated.

The efficiency of the generation function (η_TOT) shall be calculated in accordance with Formula 13:

Formula 13

The measurement set up has to allow the measurement of the 48V motor generation efficiency alone.

4.2. Demonstration of conservativeness of the 48V motor generator plus 48V/12V DC/DC converter efficiency determination U.K.

In order to use the procedure specified in 4.1 for the determination of η_TOT, it has to be demonstrated that the efficiency of the 48V motor generator alone obtained with the conditions specified in 4.1 is lower than the efficiency obtained with the conditions specified in 3.1.

4.3. Saved mechanical power U.K.

The 48 V motor generator plus the 48V/12V DC/DC converter generation function lead to saved mechanical power under real-world conditions (ΔP_mRW) and type approval conditions (ΔP_mTA) as set out in Formula 14.

Formula 14

ΔP_m = ΔP_mRW – ΔP_mTA

Where the saved mechanical power under real-world conditions (ΔP_mRW) shall be calculated in accordance with Formula 15 and the saved mechanical power under type-approval conditions (ΔP_mTA) in accordance with Formula 16:

• Formula 15

  

• Formula 16

  

where

P_RW

:

Power requirement under ‘real-world’ conditions [W], which is estimated at 750W

P_TA

:

Power requirement under type-approval NEDC conditions [W], which is estimated at 350W

η_B

:

Efficiency of the baseline alternator [%], which is 67 %

4.4. Calculation of the CO₂ savings U.K.

The CO₂ savings of the 48 V motor generator plus the 48V/12V DC/DC converter shall be calculated in accordance with Formula 17:

Formula 17

Where:

v

:

Mean driving speed of the NEDC [km/h], which is 33,58 km/h

V_Pe

:

Consumption of effective power specified in Table 2

CF

:

Conversion factor (l/100 km) - (g CO₂/km) [gCO₂/l] as defined in Table 3

4.5. Calculation of the statistical margin U.K.

The statistical margin of the results of the testing methodology caused by the measurements shall be quantified. For each operating point the standard deviation shall be calculated in accordance with Formula 18:

Formula 18

The standard deviation of the efficiency value of the efficient 48V motor generator plus the 48V/12V DC/DC converter ( ) shall be calculated in accordance with Formula 19:

Formula 19

The standard deviation of the motor generator and of the 48V/12V DC/DC converter efficiency leads to an uncertainty in the CO₂ savings ( ). That uncertainty is calculated in accordance with Formula 20:

Formula 20