update on 01 prius battery

<div class='quotetop'>QUOTE(statultra @ Sep 1 2007, 11:10 PM) [snapback]505645[/snapback]</div>

1) The motor generators are both 3 phase "brushless DC" types. The "brushless DC" means that an inverter is needed to convert a DC voltage into a rotating field by switching the motor phases to the DC bus at the right time. It also means that a shaft position sensor is needed on the motor/generator to tell the computer which phase is to be switched on. The positioning of this "phase" (compared to the magnets in the rotor) determines whether the M/G is operating as a motor or generator and controls the amount of power being transfered.

2) On the NHW 11, the inverter and battery operate at about the same voltage. By intellegently controlling the timing of the transistors that send the DC voltage to the specific phase of the motor/generators, the current flow between the the two M/Gs and the battery is controlled to match what is wanted. These algorithms are really involved. On the NHW20, there is a voltage doubling converter that takes the 200 HV battery voltage and increases it to about 500 volts. This extra conversion allows for higher efficiencies in the motors.

3) The motors of the NHW11 and NHW20 are wound differently. The NHW20 converted the parallel windings of the NHW11 to series windings to take advantage of the higher voltage. This also allows more power to be sent to the motor.

 

1) The motor generators are both 3 phase "brushless DC" types.


Could someone please explain to me how you can have a 'phase' on direct current?

 

<div class='quotetop'>QUOTE(MichaelE @ Sep 8 2007, 09:32 PM) [snapback]509272[/snapback]</div>

Hi Michael,

By taking the battery and reversing it into the motor windings. This is what the Inverter Bridge circuit does. First it hooks the battery positive to coil positive, negative to negative, then it hooks the battery positive to coil negative and negative to positive. So the coil sees voltage one-way, then the other. If done quickly enought, the current is limited by the winding inductance.

For each phase (group of windings with a 360/N, where N is the number of phases, position around the diameter) there is a bridge circuit. So that the current peaks (magnetic field peaks) in each phase can proceed around the outside diameter of motor. And the permanent magnets get pulled to those magnetic field peaks. So, a 3 phase motor has 9 windings, which are hooked together in groups of three.

Its called brushless DC, as it only needs a DC source into the motor drive (electronics) to run the motor, and it has little induced (reluctance) field. The typical mechanically comutated (coil-switched) DC motor requires brushes (sliding contacts) that make contact with various coil elements in the wound rotor of a DC motor. Due to the smaller size, and problematic cooling of the rotor, wound rotor motors are lower power, and is not nearly as durable. A brushless DC motor is built just like a three-phase AC synchrounous motor, with the coils on the inside of the stator housing and a iron rotor core. But rather than having an induction rotor core, it has a permanent magnet field rotor core. So the commutation of the coils is external to the motor, and electronic. Additionally, all coils can be driven simutaneously, but at different phases, giving excellent torque.

The typical AC motor, like the blower motor in your furnace, is an AC induction motor. It has no permanent magnets, and magnetic field is due to currents that flow in a cast aluminum conductor (socalled squirel-cage construction) that is internal to the iron core rotor. The current is induced from the magnetic fields in the stator windings. Ever notice these motor cores have an aluminum hub? That is the root of all the coil elements that are imbeded in the iron, and its cast all at once. These motors are not perfectly synchrounous. There has to be a little slip between the rotating field and the rotation RPM of the rotor to generate the current in the rotor. This is why its common for these motors to be like 1725 RPM, rather than 1800 (an interger fraction/multiple of 60 Hz).

Toyota actually specifies the Gen II motor as a synchronous AC motor. Which is correct also, but not common US motor terminology.

 

Thank you, Donee.