[NSRCA-discussion] ESC

Mike Hester kerlock at comcast.net
Wed Jul 25 14:16:17 AKDT 2007 

yeah but how many gigawatts?

-M

----- Original Message ----- 
From: "Ken Thompson" <mrandmrst at comcast.net>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, July 25, 2007 6:17 PM
Subject: Re: [NSRCA-discussion] ESC


> George,
>
> It uses the Flux Capacitor, every one knows that <VBG>
>
>
> ----- Original Message ----- 
> From: <glmiller3 at suddenlink.net>
> To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
> Sent: Wednesday, July 25, 2007 4:49 PM
> Subject: Re: [NSRCA-discussion] ESC
>
>
>> 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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>>> >> >   NSRCA-discussion at lists.nsrca.org
>>> >> >   http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>> >>
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