Jeff; I think that Rick Miller refers when say to use a high batt voltaje for a
low motor voltaje is a valid idea if you think in 'power' drawn by the motor.
In his 250V batt example; lets suppouse that the motor requires an X amp rate,
lets say 100AMP in 170V, that would be 17KWatts. That energy flowing in the
motor-controller side would be same 17KWatts in the battery-controller side
(plus a minimum lost inside the controller)
But those 17KWatts on the controller-battery side would be arround 68AMP
beeing drawn from the batts;
There it makes sense the C rate, and power. You could put the max power in
the motor, but have batts and controller 32% more relaxed than Normal. Please
correct my theory..
Rick, the only minimal 'insignificant' problem on all this avobe, either it
works or not; would be the Regen. It would be impossible to achieve, since the
controller could boost/step dn voltage from batteries but could never buck/step
up voltage from motor.
Marco Gaxiola
...facebook/EvMarch
Enviado desde mi iPhone
El 27/12/2012, a las 09:11 p.m., Jeff Major <[email protected]> escribió:
> Hi Rick,
>
> Sure you could run a higher voltage battery and set a lower output voltage
> using an AC controller. It is done all the time when motor speed is less than
> base. You could set the controller to a maximum motor phase voltage lower
> than the normal .707 Vb. Or accomplish the same thing by setting a maximum
> frequency. I am not sure why you would want to. AC motors do not have the
> voltage limitation seen with the DC commutator.
>
> The 3 phase bridge inverter used as the AC controller can be thought of as 6
> Buck converters. Or like a DC controller for each 1/2 phase. So the AC
> controller has as much control over motor voltage as a DC motor controller.
>
> I guess I don't follow your logic with regards to
> max power, C rating and all that. How would setting an artificially low
> voltage at the controller output help get more power out of the
> controller?
>
> I wouldn't say that AC lacks flexibility but rather DC is less complex there
> easier for people to apply to different situations. AC drives require tuning
> to the specific motor which is often best done by the pros at the place
> putting the system together. Once that is done the AC drive package is very
> flexible w/r/t applications and features.
>
> Regards,
>
> Jeff M
>
>
> ----- Original Message -----
> From: "[email protected]" <[email protected]>
> To: [email protected]
> Cc:
> Sent: Thursday, December 27, 2012 2:33 PM
> Subject: Re: [EVDL] 9" motor Mishap
>
> Can AC controllers function as voltage transformers in order to allow the
> use of a higher voltage battery pack in order to compensate for battery sag
> that might keep you from achieving max power and holding that power to max
> set RPM in your controller output.
> For example a modern 300V input DC controller can easily be set to an
> output voltage to match a lower motor voltage requirements. 250V in 170V out
> for a 9". The advantage here would be to reduce battery currents and keep
> them within their proper C ratings. This way you get every Kw of controller
> you paid for right up to your set RPM.
> Does this make any sense or have I missed something? Is there a lack of
> flexibility with AC or do I just have to plan better?
>
> Rick Miller
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