Division 3.3 Total efficiency and saved mechanical power

The total efficiency of the 48 V motor generator plus the 48V/12V DC/DC converter shall be calculated using Formula 3:

Formula 3

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 NEDC conditions (ΔP_mTA) as set out in Formula 4.

Formula 4

ΔP_m = ΔP_mRW – ΔP_mTA

Where the saved mechanical power under real-world conditions (ΔP_mRW) shall be calculated in accordance with Formula 5 and the saved mechanical power under type-approval NEDC conditions (ΔP_mTA) in accordance with Formula 6:

• Formula 5

  $${\mathrm{\Delta P}}_{\mathrm{mRW}}=\frac{P_{\mathrm{RW}}}{{\eta }_B}-\frac{P_{\mathrm{RW}}}{{\eta }_{\mathrm{TOT}}}$$

• Formula 6

  $${\mathrm{\Delta P}}_{\mathrm{mTA}}=\frac{P_{\mathrm{TA}}}{{\eta }_B}-\frac{P_{\mathrm{TA}}}{{\eta }_{\mathrm{TOT}}}$$

where

P_RW

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

P_TA

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

η_B

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