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Re: Capacity vs Hx (Health)

Posted: Sun Nov 03, 2019 9:52 pm
by Daklein
Turbo3 wrote: You can see the Leaf limiting power to the motor at the start.

Yes, you can see it jump up to 25 Amps but then slowly ramp up to 250 Amps. Input was accelerator pressed to the floor after the light turned Green.
Could be the end result of front wheel drive traction control. The RWD Teslas wouldn't need as much limiting for wheel slip.

Re: Capacity vs Hx (Health)

Posted: Mon Nov 04, 2019 11:46 am
by arnis
Permanent magnet motor AFAIK can't use full power at 0rpm as it gives no effect to torque. I have not confirmed that.

Re: Capacity vs Hx (Health)

Posted: Mon Nov 04, 2019 1:51 pm
by goldbrick
I think there is full torque available at 0 rpm but synchronization becomes harder the faster the motor starts. Also, the mechanical stresses introduced by rapid acceleration will be higher the larger the acceleration and jerk are. (jerk means the derivative of acceleration, not the POTUS...)

It's like the difference between allowing an ICE car with an automatic transmission to start 'gracefully' and just revving up the engine and dropping the clutches inside the transmission.

Re: Capacity vs Hx (Health)

Posted: Mon Nov 11, 2019 11:25 am
by crunchy3d
arnis wrote:
Mon Nov 04, 2019 11:46 am
Permanent magnet motor AFAIK can't use full power at 0rpm as it gives no effect to torque. I have not confirmed that.
Of course it can't use full power at speed 0. In fact, the power is 0. Why?

Power = Torque * rotational speed

If speed is 0, mechanical power is 0, but torque can still be significant. In fact most EV have maximum torque from zero speed to some specific speed where Torque * rotational speed = Max power. From this speed on the power remains constant (the maximum one) and torque starts to drop according to equation

Torque = (Max power)/rotational speed