[NSRCA-discussion] ESC

[Fred Huber]

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
>>
>> _______________________________________________
>> NSRCA-discussion mailing list
>> NSRCA-discussion at lists.nsrca.org
>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>>
>> _______________________________________________
>> NSRCA-discussion mailing list
>> NSRCA-discussion at lists.nsrca.org
>> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>
> _______________________________________________
> NSRCA-discussion mailing list
> NSRCA-discussion at lists.nsrca.org
> http://lists.nsrca.org/mailman/listinfo/nsrca-discussion
>
>
>
> -- 
> No virus found in this incoming message.
> Checked by AVG Free Edition.
> Version: 7.5.476 / Virus Database: 269.10.19/917 - Release Date: 7/25/2007 
> 1:16 AM
>