Total output vs. performances in single speed EV
▶ Comparing to ICE with the same output, EV should have outstanding performances in all areas with superior torque-rpm characteristics to engine’s. However, performances
(top speed, gradeability, passing acceleration) of single speed EV with double output than ICE
are inferior to ICE’s
, except initial accelerations.
▶ Weak points of single speed EV using field weakening control (FWC): overheat at higher speed range
(half of electric
energy in battery is not converted into kinetic energy, wasted as a heat
.) Overheat results in performance damage in
▶ Overheat at maximum output has negative effects on motor and inverter, which should be temporally used (10~20
Driving system of NHC 6AT
▶ It always use rated torque (rated current) and rated rpm (rated voltage) at any speed, which is 1/3 to single speed EV
Max permitted current is 1.5 times of rated current, which is temporally used without overheat of motor and inverter.
▶ NHC 6AT with smaller motor than single speed
provides wider range of torque and rpm
without using FWC.
▶ With narrowing gear change ratio of compact 6-speed gearbox, it makes motor rotate at the most efficient rated range at any speed
▶ Initial battery energy is saved by starting and accelerating from lower gear to higher gear
Current(A) is proportionally consumed to loads.
▶ Max current
is permitted to 1.5 times of rated current
at power mode “ON”. ⇒ Rarely used
• Automatically “OFF” if permitted time (about 5 minute) is passed, and/or temperature of motor is saturated.
• Continuous driving vehicle over rated output without water cooling system makes temperature of motor be over
saturated, which radically drop motor efficiency as shown in above graph and motor get seriously damaged.