<div dir="ltr">Hello, Motorheads~ and with a cc to SolarConverters since I'm casting in all directions for answers.<div><br></div><div>Another "solar guy" left our town & abandoned a pond aeration system. The owners asked me to be their "new guy", but we're struggling with motor problems way too soon.</div>
<div><br></div><div>+++++++++++++++++++++++</div><div><br></div><div>Original setup: Twelve 36 cell (~60 watt) Solarex modules wired all parallel, driving a SolarConverters PPT12/24-30 "power pump tracker". The original array wiring work had to be redone. The S-C controller was configured to MPPT the ~17 volt array input and the control was factory defaulted to clamp the motor output at no more than 15vDC, as appropriate for the original "12 volt" air motors. </div>
<div><br></div><div>The Gast DC air motors are the type that pump up the airbrakes in big trucks. Each compressor head is direct coupled to a permanent magnet motor with the familiar look of old school Pacific Scientific aka Honeywell motors. The original 12v motor-compressors were well worn so we rewired the array ~34v MPPT, jumpered the SolarConverters controller to match, and bought the 24 volt version of the same type air motors. Another jumper in the S-C controller sets it to clamp the output at no more than 30v DC.</div>
<div><br></div><div>Gast says no problem if their "24 volt" air motor is fed 30 volts since they assume the truck alternator can push the voltage that high. We're loading those motors way lower than what they're rated for since we're only pushing air to the bottom of a nearby pond. The existing 30 amp controller seems "super sized" compared to what the motors need and the PV array is also way bigger than what the motors really need. My clamp meter is broke right now--which makes me feel like an amputee--so I can't get fresh numbers today but each motor only drew a few amps @ 30 volts when last I checked. </div>
<div><br></div><div>Two motors are connected in parallel to the output of the single SolarConverters motor controller so <b><i>maybe that's a key to our problem:</i></b> the motors do not start reliably and this misbehavior is very unpredictable. When the 24v motors were new--around 2011--these problems did not present until after several months had passed. Tapping on a motor shell (as one may do with a balky car starter) sometimes gets it to spin up, so I think they're not commutating properly. We took one motor apart and the commutator bars looked badly chewed up. The brushes looked OK where they rub on the comm and the brushes still have some length left. Some cleanup effort on the comm bars improved things with that motor. </div>
<div><br></div><div>++++++++++++++++++++++++++++++ </div><div><br></div><div>With both motors wired parallel--but obviously they won't commutate in synch with one another--I wonder if back emf from one motor (maybe when the brush crosses the commutator gap) might be spiking the other motor with a voltage surcharge that causes arcing at the brush/commutator interface? My DC voltmeter shows 30 volts steady at the motor screws but it's not a fancy meter and it may not be able to capture a higher voltage flicker.</div>
<div><br></div><div>My client and I are frustrated, hoping for a logical explanation, and also looking for plan C to implement. The fish endure stress leading to death whenever the aeration fails, so I hope to get past these nervous times soon.</div>
<div><br></div><div>* Could we add capacitance across each set of motor screws...or a zener diode? If so, how would I determine values to try?</div><div><br></div><div>* Should we special order the SolarConverter with a flat 24 volt voltage clamp set by the factory instead of their standard 30 volt clamp?</div>
<div><br></div><div>* Should we split things up with a dedicated controller for each motor? In that event, must we dedicate part of the PV array to each SolarConverter or can two controllers share the same overall solar array power supply? (All the glass is in the same plane, and partial shade only occurs during sunrise and sunset times.) </div>
<div><br></div><div>Thanks as always for being the "Motorheads Nonpareil". </div><div><br></div><div>Jolliness,</div><div><br clear="all"><div>Mick Abraham, Proprietor<br><a href="http://www.abrahamsolar.com" target="_blank">www.abrahamsolar.com</a><br>
<br>Voice: 970-731-4675</div>
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