Re: [CAD_CAM_EDM_DRO] Re: H-BRIDGE and DC-SERVO DRIVE improvement help!

----- Original Message -----
From: "Asim Khan" <asimtec@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, May 06, 2003 12:05 PM
Subject: [CAD_CAM_EDM_DRO] Re: H-BRIDGE and DC-SERVO DRIVE improvement help!


> thanks dave for such an helpful information
> oh pc cant generate such a high frequency PWM!! i have plan to
> generate this PWM signal through use of some comparator chips some
> triangular wave generators made up of opamps.
> I' havent done that yet but i will do that. there is information
> available on net for PWM generators for dc motor:
> http://www.solorb.com/elect/solarcirc/pwm1/
>
> or maybe i will use some 8051 compatible microconroller to do this
> PWM stuf.
> regards
> @sim,
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
> <davemucha@j...> wrote:
> > check out,
> >
> > http://www.armory.com/~rstevew/Public/Motors/H-Bridges/Blanchard/h-
> > bridge.htm
> >
> > I'm not sure about the speed of switching for the transistors, but
> it
> > appears that you are not addressing any back EMF unless it is
> handled
> > by the darlintons.
> >
> > and it if I am not mistaken, MOSFET's will be easy to size for the
> > voltage and amps.
> >
> > Also, what software are you using ? and what dwell time do you have
> > for the on time and off time between pulses ?
> >
> > Dave
> >
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Asim Khan" <asimtec@y...>
> > wrote:
> > > Hi forum:
> > >
> > > I had build the H-Bridge by looking at this following
> > > design:
> > >
> > > http://cet.ssu.portsmouth.oh.us/~jlindeman/h-bridge/hbridge.html
> > >
> > > This above design uses PNP and NPN DARLINTON BJTS TIP12X series
> in
> > > its
> > > design. This design works ok as far as the switching frequesny
> > > applied is no more than 3~4Khz. I had put it in an application
> > where
> > > the PWM freqyncy is 11.7KHz. at high frequenies this design
> fails,
> > > burning transistors.
> > > I had tested this desin in my lab and i found that when you drive
> > the
> > > left PNP darlinton and the right NPN darlinton by appliying the
> PWM
> > > signal at left side then the right side PNP darlinton starts
> > getting
> > > heat up, when the PWM frequency is 10~20Khz, and eventually the
> > right
> > > side PNP darlinton blasts!!
> > > It seems the the right side PNP darlinton recieves the driving
> > pulses
> > > when it should not get driven. since in an hbridge at a single
> > moment
> > > there only two transistors should conduct, and in my case 3
> > > transitors starts conducting which causes so much high current
> > > through the transitor.
> > > same happens when i apply the PWM signal at right hand side, but
> > this
> > > time the left side PNP darlinton starts getting heatup
> > >
> > > I had also tried MJ11032(NPN) AND MJ11033(PNP) darlinton high
> speed
> > > switch transistors(specially designed for hi amp inductive load
> > > swithching) with 50AMP continuos current capability in my
> > > circuit. but observations were the same.
> > > I need to design a professional dc-servo drive which can operate
> > upto
> > > 80V and can deleiver around 20-30AMP.
> > >
> > > please suggest what changes should i made in this schematic so
> that
> > > i can use this H-BRIDGE design for HI frequency PWM signals and
> for
> > > hi amp loads !
> > > i request everyone to please suggest me any designs and or links
> > > best regards
> > > @sim
>
>
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