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<DIV><FONT face=Arial size=2>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.</FONT></DIV>
<DIV><FONT face=Arial size=2>--Lance</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<BLOCKQUOTE
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=humptybump@sbcglobal.net
href="mailto:humptybump@sbcglobal.net">Richard Lewis</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">'NSRCA Mailing List'</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, July 24, 2007 4:57
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] ESC</DIV>
<DIV><BR></DIV>
<DIV class=Section1>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Nat,<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">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.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">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.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">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.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">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.<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial">Richard<o:p></o:p></SPAN></FONT></P>
<P class=MsoNormal><FONT face=Arial color=navy size=2><SPAN
style="FONT-SIZE: 10pt; COLOR: navy; FONT-FAMILY: Arial"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<DIV class=MsoNormal style="TEXT-ALIGN: center" align=center><FONT
face="Times New Roman" size=3><SPAN style="FONT-SIZE: 12pt">
<HR tabIndex=-1 align=center width="100%" SIZE=2>
</SPAN></FONT></DIV>
<P class=MsoNormal><B><FONT face=Tahoma size=2><SPAN
style="FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">From:</SPAN></FONT></B><FONT
face=Tahoma size=2><SPAN style="FONT-SIZE: 10pt; FONT-FAMILY: Tahoma">
nsrca-discussion-bounces@lists.nsrca.org
[mailto:nsrca-discussion-bounces@lists.nsrca.org] <B><SPAN
style="FONT-WEIGHT: bold">On Behalf Of </SPAN></B>Nat Penton<BR><B><SPAN
style="FONT-WEIGHT: bold">Sent:</SPAN></B> Tuesday, July 24, 2007 3:26
PM<BR><B><SPAN style="FONT-WEIGHT: bold">To:</SPAN></B> <st1:PersonName
w:st="on">NSRCA Mailing List</st1:PersonName><BR><B><SPAN
style="FONT-WEIGHT: bold">Subject:</SPAN></B> [NSRCA-discussion]
ESC</SPAN></FONT><o:p></o:p></P></DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"><o:p> </o:p></SPAN></FONT></P>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">OK, I need
educating.</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">I realize the ESC converts single
phase to three phase. Does it alter the speed of the motor by changing
amplitude or frequency ?</SPAN></FONT><o:p></o:p></P></DIV>
<DIV>
<P class=MsoNormal><FONT face="Times New Roman" size=3><SPAN
style="FONT-SIZE: 12pt"> <o:p></o:p></SPAN></FONT></P></DIV>
<DIV>
<P class=MsoNormal><FONT face=Arial size=2><SPAN
style="FONT-SIZE: 10pt; FONT-FAMILY: Arial">Why did it burn up the ESC (fast,
like in quick) when I accidently single phased
? TIA
Nat</SPAN></FONT><o:p></o:p></P></DIV></DIV>
<P>
<HR>
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