Great then explain (96-72) x .08 = 300 amps. How will the controller going to see 24 volts
Sent from my iPhone > On Sep 14, 2017, at 4:54 PM, Cor van de Water via EV <ev@lists.evdl.org> > wrote: > > Paul, > It seems you have difficulty grasping some concepts presented here, > you would do well by studying them further before commenting. > Maybe you just read too casually or fast that you missed what was being > explained to you. > > You have the right to not believe what anyone says. > Wise people listen to wise advise is all I want to offer. > Cor. > > -----Original Message----- > From: EV [mailto:ev-boun...@lists.evdl.org] On Behalf Of paul dove via EV > Sent: Thursday, September 14, 2017 11:10 AM > To: Roger Stockton; Electric Vehicle Discussion List > Cc: paul dove > Subject: Re: [EVDL] Slow due to 96V pack? > > There is no voltage adjustment on input voltage in any motor controller I > ever used. > The PWM only controls the output voltage by switching it on and off. The duty > cycle then sets the average voltage the motor sees. > It may have a low voltage cutoff circuit but that just shuts down the output > in the event the battery falls below 72volts.... thus the controller would > not be working if the voltage was 96-72 = 24volts. > And yes hooking batteries straight up you would have no control over the > current but I still don't believe lead acid would put out 1200 amps. > > From: Roger Stockton <rstock...@delta-q.com> > To: Electric Vehicle Discussion List <ev@lists.evdl.org> > Cc: paul dove <dov...@bellsouth.net> > Sent: Thursday, September 14, 2017 12:19 PM > Subject: RE: [EVDL] Slow due to 96V pack? > > paul dove wrote: > >> That made no sense to me but a DC motor controller takes the input >> voltage to power mosfets or igbts which switch the power on and off >> with a pwm signal to get the desired output to drive a motor. It has >> no knowledge of the battery impedance. > > The controller does not have, or need, knowledge the battery impedance; this > is simply Ohms Law at work. > > The controller PWMs the power from the battery, and the duty cycle of the PWM > can be varied to limit whatever parameter the controller logic cares about at > any given time: input voltage, input current, output voltage, or output > current. > > Since the battery has a finite, non-zero internal impedance, its terminal > voltage will sag as current is drawn from it. If the motor controller > enforces a minimum input (battery) voltage (as does the controller in > question), then its logic will vary/limit the PWM duty cycle to prevent the > voltage at the input of the controller from falling below the target level. > > Since the controller logic will limit/vary the input current to prevent the > input voltage from falling below the threshold, then the maximum voltage > difference across the battery internal resistance is the open circuit battery > voltage minus the minimum input voltage limit of the controller: 96V - 72V = > 24V, in this example. > > The controller does not know what the internal impedance of the battery is, > but Ohms Law still applies to limit the maximum current from the battery to > *whatever* value results in 24V drop across the internal resistance: 24V / > 0.08 ohms = 300A in this example. > > *IF* the sophisticated controller were replaced with a simple contactor > controller, then if the contactor controller allowed the entire 96V battery > to be connected directly to a stalled motor (~0 ohms), the voltage drop > across the battery internal resistance would ~approach~ 96V - 0V = 96V, and > the peak current into the motor would approach 96V / 0.08 ohms = 1200A. > > Hope this helps, > > Roger. > > > > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20170914/9002cb7f/attachment.html> > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing > at NEDRA (http://groups.yahoo.com/group/NEDRA) > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > Read EVAngel's EV News at http://evdl.org/evln/ > Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA) > _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org Read EVAngel's EV News at http://evdl.org/evln/ Please discuss EV drag racing at NEDRA (http://groups.yahoo.com/group/NEDRA)
