<html><head></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">No the peak current will be lower at low rpm. The motor is an inductor that resists current flow especially at high frequency. Low duty cycle means very short pulses that so the current doesn't build up to its potential peak before the FETs open up and turn off the current from the battery. However, the ESC has a free-weeling diode that takes the energy stored in the motor to supply current during the time the switch is off so the current doesn't drop to zero. The motor/diode circuit has a kind of flywheel action. Give it short input pulses and it goes slow and long ones and it goes fast.<div><br></div><div>Jim O</div><div><br></div><div><br><div><div>On Mar 15, 2012, at 10:52 PM, Ed Alt wrote:</div><br class="Apple-interchange-newline"><blockquote type="cite">
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<div style="FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: 12pt">
<div>Jim:</div>
<div> </div>
<div>I was thinking along the same lines, but maybe what Peter is driving at is
that current peaks will be greater at lower RPMs. I think that might be
true, not entirely sure though.</div>
<div> </div>
<div>Ed</div>
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<div style="BACKGROUND: #f5f5f5">
<div style="font-color: black"><b>From:</b> <a title="joddino@socal.rr.com" href="mailto:joddino@socal.rr.com">James Oddino</a> </div>
<div><b>Sent:</b> Friday, March 16, 2012 1:15 AM</div>
<div><b>To:</b> <a title="nsrca-discussion@lists.nsrca.org" href="mailto:nsrca-discussion@lists.nsrca.org">General pattern discussion</a>
</div>
<div><b>Subject:</b> Re: [NSRCA-discussion] Plettenberg 30-10 evo and Jeti
ESC</div></div></div>
<div> </div></div>
<div style="FONT-STYLE: normal; DISPLAY: inline; FONT-FAMILY: 'Calibri'; COLOR: #000000; FONT-SIZE: small; FONT-WEIGHT: normal; TEXT-DECORATION: none">Let's
look at this from a logic standpoint.
<div>1) We limit the duty cycle to decrease the rpm. Lower duty cycle
means lower average voltage, therefore lower rpm. RPM= Kv*V</div>
<div>2) Let's say we cut the voltage and therefore the rpm in half. The
power to turn the prop required would be much less than half because power
varies with the cube of rpm.</div>
<div>3) Therefore, if power is reduced by more than half the current will be
reduced as well as the voltage.</div>
<div> </div>
<div>In our modern day speed controllers the current through the motor does not
go full on/full off with the duty cycle but remains relatively constant through
the cycle due to the ESC design and motor characteristics. The peak
current during the on portion of the cycle is lower than the current at 100%
duty cycle. Limiting duty cycle does reduce the current and the power
consumption. Does it limit power dissipation in the ESC? That is
another question.</div>
<div> </div>
<div>Jim O</div>
<div>
<div> </div>
<div>
<div>On Mar 14, 2012, at 9:59 PM, Peter Vogel wrote:</div><br class="Apple-interchange-newline">
<blockquote type="cite">potentially, yes. The most efficient running of
the ESC is WOT. An electric motor is a constant speed system, it
will draw whatever amps it needs in order to spin at the speed defined by the
kV * received voltage for however long it receives voltage. The motor
will pull the amps it wants to during each pulse from the ESC. That'll
obviously depend on all kinds of factors including the weight + size of the
prop, whether you are in an up or downline, etc.
<div> </div>
<div>Peter+<br>
<div>
<div> </div>
<div class="gmail_quote">On Wed, Mar 14, 2012 at 9:45 PM, James Oddino <span dir="ltr"><<a href="mailto:joddino@socal.rr.com">joddino@socal.rr.com</a>></span>
wrote:<br>
<blockquote style="BORDER-LEFT: #ccc 1px solid; MARGIN: 0px 0px 0px 0.8ex; PADDING-LEFT: 1ex" class="gmail_quote">Can you elaborate? Are you saying more current flows
at lower duty cycle than it does when the FETs are full on at high
throttle?<br><br>Jim O<br>
<div class="im HOEnZb"><br><br>On Mar 14, 2012, at 9:15 PM, Peter Vogel
wrote:<br><br>> Limiting throttle does NOT limit current to the motor, in
fact, it can cause higher current draw. All throttle does is vary the
on vs off cycle during which voltage is sent to the motor.<br>><br>>
Peter+<br>><br>> Sent from my iPhone4S<br>><br>><br></div>
<div class="HOEnZb">
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