<p>Starter motors are sensitive for overheating. By estimating the temperature and</p><p>preventing cranking in time, there is an option to avoid the dangerous temperatures.</p><p>The truck manufacturer Scania CV AB proposed a master thesis that</p><p>should evaluate the need of an overheating protection for the starter motor.</p><p>The aim is to evaluate any positive effects of implementing an algorithm that</p><p>can estimate the brush temperature instead of using the available time constrain,</p><p>which allows 35 seconds of cranking with a following 2 seconds delay, allowing the</p><p>crank shaft to stop before a new start attempt is allowed. To achieve high load</p><p>on the starter motor and high temperature in the brushes, tests were performed</p><p>under</p><p>Initial testing on truck, under normal temperatures, showed that the batteries</p><p>could not run the starter motor long enough to reach high temperatures in the</p><p>brushes. This is believed to be caused by the voltage drop between the batteries</p><p>and the starter motor, causing the starter motor to run in an operating area it</p><p>is not optimized for. There are several other problems which gives a higher load</p><p>on the engine, for example oil viscosity, resulting in higher currents, but those are</p><p>not mentioned in this report.</p><p>Three different models are compared, Two State Model, Single State Model</p><p>and a Time Constrained Model. Tests and verifications show that the Two State</p><p>Model is superior when it comes to protecting the starter motor from overheating</p><p>and at the same time maximizing the cranking time. The major difference between</p><p>the Two State Model and the Single State Model are the cooling characteristics.</p><p>In the Single State Model the brush temperature drops quickly to the outside</p><p>temperature while in the Two State Model the brush temperature drops to a</p><p>second state temperature instead of the outside temperature. With the currently</p><p>implemented time constrain it is possible to overheat the starter motor. The</p><p>algorithms are optimized under cold conditions, due to problems in reaching high</p><p>temperatures under warmer conditions.</p><p>−20 Celsius.</p>
| Identifer | oai:union.ndltd.org:UPSALLA/oai:DiVA.org:liu-57309 |
| Date | January 2010 |
| Creators | Gerhardsson, Daniel |
| Publisher | Linköping University, Vehicular Systems |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, text |
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