[bwilson4web]

Hi,

I get the Toyota press releases and the recent technical specs on the Lexus 250h and 450h are impressive:

Lexus_450h said:

ELECTRIC MOTORS
Motor Generator 1 (MG1) - Function
Generator, engine starter, transmission ratio control
- Type
Permanent magnet motor
- Max. voltage
AC 650V
Motor Generator 2 (MG2) - Function
Drives front wheels, regenerative braking
- Type
Permanent magnet motor
- Max. voltage
AC 650V
- Max. output
167 hp (123 kW)
Motor Generator Rear (MGR) - Function
Drives rear wheels, regenerative braking
(AWD Model Only) - Type
Permanent magnet motor
- Max. voltage
AC 650V
- Max. output
68 hp (50 kW)
HYBRID BATTERY PACK
Type
Sealed Nickel Metal Hydride (Ni-MH)
Nominal Voltage
Power Output
288V
37 kW

Also,

Lexus_250h said:

ELECTRIC MOTORS
Motor Generator 1 (MG1) - Function
Generator, engine starter, transmission ratio control
- Type
Permanent magnet motor
- Max. voltage
AC 650V
Motor Generator 2 (MG2) - Function
Drives front wheels, regeneration during braking
- Type
Permanent magnet motor
- Max. voltage
AC 650V
- Max. output
141 hp (105 kW)
HYBRID BATTERY PACK
Type
Sealed Nickel Metal Hydride (Ni-MH)
Nominal Voltage
244.8V

What first attracted my attention were the voltages, 650V. This is important because it means "field weaking," a technique needed by lower voltage motors, is avoided. What happens is as the motor spins faster, the motion generates a voltage opposite the power (aka., back EMF.) To counteract this, the power timing is changed to allow more power in but less efficient. The higher voltage means the power can overcome the back EMF and run at a higher efficiency.

The second 'heads up' was the rear motor of the 450h is about the engine power of my NHW11 Prius. The MG2 power of the 250h is the total power from my NHW11 Prius. What we're seeing is electric motor systems, the inverter and battery, that are functionally in the same power range as my primary commuting car.

The third was the variable voltages of the traction battery packs. I've long suspect the inverters are more than capable of handling traction batteries sized for the vehicle mission. The implication is that traction battery configuration becomes a part that can be sized for the vehicle. The implication is traction battery sizing is no long a major engineering task, at least for NiMH batteries, but a much simpler, formula derived subsystem. This means sizing the traction battery for the vehicle without spending substantial effort tailoring for the vehicle. It has arrived as a stock, standard, vehicle part.

Bob Wilson