[NSRCA-discussion] ESC

[glmiller3 at suddenlink.net]

Fred,

I can see how that senses the rpm to adjust the "phasing speed" but how does it sense the "flux" of the magnets?

George
---- Fred Huber <fhhuber at clearwire.net> wrote: 
> The simulated AC supplied by the ESC leaves one phase "dead" appx 1/4 of the 
> time.  Durring that time, the ESC senses the "counter EMF" generated by the 
> magnets passing the de-energized windings.
> 
> If the ESC didn't have this feedback, it would need a hall sensor to detect 
> rpm.  Early 3-phase ESC's had the hall sensors. (and actually thats a better 
> way to do it)
> 
> ----- Original Message ----- 
> From: <glmiller3 at suddenlink.net>
> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> Sent: Wednesday, July 25, 2007 9:35 AM
> Subject: Re: [NSRCA-discussion] ESC
> 
> 
> > So (to check my understanding at the risk of being repetitive)- the ESC 
> > changes the voltage to maintain the magnetic flux of the rotor and changes 
> > the frequency to increase the RPM ?!
> >
> > So how does it detect the magnetic flux?
> >
> > And how come your running a 4stroke if you are such an electric guru?<G>
> >
> > G
> > ---- Richard Lewis <humptybump at sbcglobal.net> wrote:
> >> George,
> >>
> >> It is the unit of measure related to the strength of the magnetic field
> >> produced by the windings.
> >>
> >> Richard
> >>
> >> -----Original Message-----
> >> From: nsrca-discussion-bounces at lists.nsrca.org
> >> [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of
> >> glmiller3 at suddenlink.net
> >> Sent: Wednesday, July 25, 2007 6:10 AM
> >> To: NSRCA Mailing List
> >> Subject: Re: [NSRCA-discussion] ESC
> >>
> >> Richard,
> >>
> >> What is the "flux" in the motor?
> >> Thanks
> >> George
> >> ---- Lance Van Nostrand <patterndude at tx.rr.com> wrote:
> >> > Thanks Richard.  I thought the motors were multiphase DC motors and the
> >> ESC sequentially energized the windings at the desired rpm and increased 
> >> the
> >> voltage when the stator fell too far behind.
> >> > --Lance
> >> >
> >> >   ----- Original Message ----- 
> >> >   From: Richard Lewis
> >> >   To: 'NSRCA Mailing List'
> >> >   Sent: Tuesday, July 24, 2007 4:57 PM
> >> >   Subject: Re: [NSRCA-discussion] ESC
> >> >
> >> >
> >> >   Nat,
> >> >
> >> >
> >> >
> >> >   The ESC has a set of transistors arranged in a three phase bridge
> >> arrangement.  The 3-phase bridge is supplied by the DC from the batteries
> >> and through a complex switching algorithm it synthesizes a three phase AC
> >> voltage that is applied to the motor windings.  The motor is a permanent
> >> magnet synchronous AC motor.  The speed of a synchronous machine is 
> >> directly
> >> proportional to the speed of the rotating magnetic field applied.  The
> >> voltage applied to the motor is in short pulses at a fixed frequency know 
> >> as
> >> the carrier frequency.  The width of these pulses is modulated (pulse 
> >> width
> >> modulation or PWM) to produce an average voltage waveform that 
> >> approximates
> >> the sinusoidal shape required to operate the motor efficiently.  The
> >> amplitude of the synthesized sinusoidal voltage waveform is varied
> >> proportionally with the frequency to produce the proper flux within the
> >> motor for a given frequency.
> >> >
> >> >
> >> >
> >> >   To answer the question, the speed controller varies the frequency to
> >> control the speed of the motor.  The ESC varies the voltage to control 
> >> the
> >> flux in the motor.
> >> >
> >> >
> >> >
> >> >   The single phase case would cause the connected windings to draw
> >> excessive current without the third phase to balance the effective 
> >> impedance
> >> in the motor winding and take out the transistors easily.
> >> >
> >> >
> >> >
> >> >   In modern industrial Variable Frequency Drives (VFD) the transistors
> >> have many protection mechanisms from fuses which are relatively slow to 
> >> an
> >> internal gate cutoff that can stop excessive current within a single 
> >> pulse
> >> to protect the transistor from damage due to excessive current.  In
> >> comparison, the ESC's we use have little or no protection from excessive
> >> current.
> >> >
> >> >
> >> >
> >> >   Richard
> >> >
> >> >
> >> >
> >> >
> >> >
> >> ----------------------------------------------------------------------------
> >> --
> >> >
> >> >   From: nsrca-discussion-bounces at lists.nsrca.org
> >> [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of Nat Penton
> >> >   Sent: Tuesday, July 24, 2007 3:26 PM
> >> >   To: NSRCA Mailing List
> >> >   Subject: [NSRCA-discussion] ESC
> >> >
> >> >
> >> >
> >> >   OK, I need educating.
> >> >
> >> >   I realize the ESC converts single phase to three phase. Does it alter
> >> the speed of the motor by changing  amplitude or frequency ?
> >> >
> >> >
> >> >
> >> >   Why did it burn up the ESC (fast, like in quick) when I accidently
> >> single phased ?           TIA   Nat
> >> >
> >> >
> >> >
> >> >
> >> ----------------------------------------------------------------------------
> >> --
> >> >
> >> >
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