[NSRCA-discussion] ESC

Ken Thompson mrandmrst at comcast.net
Wed Jul 25 14:35:20 AKDT 2007 

I believe I will have to research some of my old DVD's to find that answer, 
however, it has something to do with the charge of a lightning bolt near a 
clock tower.


----- Original Message ----- 
From: "Mike Hester" <kerlock at comcast.net>
To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
Sent: Wednesday, July 25, 2007 5:16 PM
Subject: Re: [NSRCA-discussion] ESC


> 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
>>>> >> >
>>>> >> >
>>>> >> >
>>>> >> >
>>>> >> ----------------------------------------------------------------------------
>>>> >> --
>>>> >> >
>>>> >> >
>>>> >> >   _______________________________________________
>>>> >> >   NSRCA-discussion mailing list
>>>> >> >   NSRCA-discussion at lists.nsrca.org
>>>> >> >   http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>>> >>
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>>>> >
>>>> >
>>>> > -- 
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>>>> > 1:16 AM
>>>> >
>>>>
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