So something I have understood for over 40 years. Electric motors running at full load 24/7 will last longer in hours run by in some cases 2 times that of cycling loads and up to 4 times longer on those motors that start and run for short periods say 10 to 30 minutes at a time. A continuous rating is something that runs for 2 hours or more at full load in the Ontario Electrical code, depending on what information you use, Nema standard is 3 hours at full load, there are other factors such a service factor, most of what I am saying here will mean absolutely nothing to 98% of the membership. I copied the link below as it has ratings referred to as insulation classes and hours of operation, note page #8, as a example I mentioned class F at 155'C , this has a direct bearing on life of the winding. This link would be extremely useful to anyone in the electrical service or installation of electric motors.
RATED TEMPERATURE RISE OR INSULATION CLASS
So heat Cycle relating to Series and Shunt regulators/ Varying load / Fixed load
Tow things to be aware of , varying load and heat cycle. Varying load, many don't realize the shunt regulator starts working at or above roughly 14.5 to 15 Volts DC. So at idle the shunt regulator has 6 diodes that transform AC to DC, the stator provides the wattage
required to run the motorcycle , I refer to this as base load, as the RPM increases, the stator output in the form of Volts AC
increases, this in turn causes a increase directly proportional in Volts DC. I have mentioned cooking the AGM battery, which battery will last longer, one charged at 14.2 VDC or one that sees 14.5 to 15 Volts DC, yes I know the answer. Cycling load, once we activate the shunt part of the regulator
14.5 VDC - 15 VDC , we start wasting Watts
to ground. So to interrupt my explanation, those with incandescent lights , incandescent signal lights , heated gear, accessory outlets, switching to LED or trying to reduce load, concern about overloading the stator is unfounded, because anything in excess of 14.5 VDC - 15 VDC, will be shunted to ground in the form of heat.
Now to the meat of this discussion, at 1350 to 1500 RPM idle ( I run 1500 because that keeps output at 13.9 VDC with my fan of something like 70 Watts running), heat cycle with a Shunt regulator, at idle we have what I refer to base load, somewhere around 160 to 180 watts
( keep highlighting watts as that is energy/ work done , work is volts times amps = watts, you can have volts and no work done). So once you reach 3500 to 4000 RPM the stator is capable of outputting full 330 watts
, going above 3500 - 4000 RPM accomplishes very little, so your shunt regulated motorcycle stator is wasting if we use the base load of 180 watts , it is wasting 150 Watts.
And finally why this is a problem, copper expands and contracts much more than steel ( laminations https://www.google.ca/url?sa=t&rct=j...n9jk-NA_w0FU64
expansion and contraction ) The magnet wire https://en.wikipedia.org/wiki/Magnet_wire
coating is typically smaller than a human hair, again most of this information will mean nothing to 98% of the membership.
This expansion and contraction will occur every-time you go from 3500-4000 RPM and higher back to idle, as the oil is trying to cool the stator.
When winding is done, it is usually either dipped in a now epoxy coating, encapsulated or years ago a varnish dip and bake, this purpose was to prevent movement of the magnet wire. If anyone has ever watched someone welding using high current with both the ground and electrode cable traveling 15 feet or more, will notice the cables jump every-time a arc is struck , that is a direct result of the magnetic field change.
Since our Stator has a rotating permanent magnetic field, every-time it passes across the magnet wire, the collapsing field of the magnet wire is equal to and opposite the applied force, between the expansion and contraction of the winding on RPM change, eventually some looser turn start moving and that less than a human hair insulation wears off and a turn to turn short occurs. So consider a day ride where you start and stop say 3 times, all lasting 10 minutes or more, in addition to the numerous heat cycles during RPM change you also have cooling below normal operating temperature. Will stop here, next Series Regulator and why your stator will last indefinitely.
I am not going into detail how it works , but the why and differences. First I am going to point out for those that have no clue what I said above
In my stator testing and my Polaris install I mention to test your stator before you convert from Shunt to Series at 2000 RPM using your idle screw, if you have more than 1 VAC difference between phases your stator is toast or to explain what will happen next if you switch to a series regulator, imminent failure will occur
. The reason is because you already have a turn to turn short, in fact for those reading this and they are switching, running at 3000 RPM with the idle screw would be even better, strictly to find if you have a turn to turn short, and this test would be better run once the motor is up to temperature, at that point the copper winding has expanded . The reason for this is because instead of loading / shorting the stator at or above 14.5 to 15 VDC, the series regulator starts switching around 14.2 VDC, what happens is the total watts
output never changes , that is if you need 180 watts
, that is all that is produced, yes there is a catch , much like a light dimmer in your home, the Series regulator starts switching, the higher the RPM the higher the switching, the end result is the VAC will rise, only the portion that is required to keep at 14.2 VDC is used, so it is possible to have 36 to 48 VAC across phases with a series regulator, so with a already damaged magnet wire stator, that higher voltage will speed up the failure .
Two very important points to remember, my stator with what is now a 4016868 Polaris regulator , only sees roughly 180 watts all the time, which is roughly 55% load, the heat produced is much less as the circular mills per amp is greater because of the reduced current. When I am riding with my heated gear and heated grips, it is colder out, again that load is fixed, some cycling does occur because at idle my stator can't keep up with my Gerbing jacket load, howver my stator never sees full load, unless I am riding at night, high beam on with heated gear, and the fan running. So with a series regulator , a fraction of the heat cool cycles of the shunt.
I am sure I missed something, this forum is open to questions, feel free to ask.