WorldWide Drilling Resource

Tractor Transformation by Britt Storkson Owner, P2FlowLLC You’ve heard a lot about gas-elec- tric hybrid cars lately. To be with the “in” crowd, I built a generator-powered gas- electric hybrid garden tractor. No, actually I built it to test out VFDs (variable frequency drives) to determine if they were suitable for water pumping. I also wanted to test how well they stood up under various conditions they probably would not encounter in a pump house. I am pleased to report my gas-elec- tric hybrid garden tractor works very well and has served me reliably for several years now. It’s a 4400-watt 230-volt gasoline-powered single-phase gener- ator that runs a three-horsepower 240- volt three-phase motor through a VFD. In its previous life, this was a 1976 Simplicity tractor. It’s built like a tank with a lot of steel and, of course it’s fairly heavy. I installed a 13-gallon fuel tank where the rotary mower would be. An electric fuel pump delivers fuel to the generator motor. As a safety fea- ture, I installed a relay to shut off the fuel delivery if the generator stops, this way the fuel does not continue to be pumped to a hot engine when it is not running. I made a “joystick” drive control to stop and start the tractor and adjust the speed. Push the joystick forward and the tractor moves forward; pull it back and it moves backward. The farther you push the joystick the faster it goes. The middle position is a stop signal. The VFD even provides motor braking to slow the tractor when it is going down hills to maintain the desired speed. It’s underpowered because I want- ed to keep it as inexpensive as possi- ble, but it is adequate for just about any task. It can climb very steep hills as long as the load is applied smoothly. When I hit a bump or roll over a rock, the VFD quits and indicates overload on the dis- play. VFDs are designed to handle only so much power going through them, depend- ing on the horsepower rating. Power is watts. Volts times amps equals watts. Since the voltage is fairly consistent, the amperage changes when the load (torque output by the motor) changes. The amperage is directly proportional to the load, so the amperage goes up when the load increases, and goes down when the load decreases. Since horsepower is torque over time, one can “spread out” the load over time so there is a smaller load placed on the motor. You still get up the hill, you just climb the hill slower. Uniformly loading the VFD is important because an amperage “spike” will shut down the VFD immediately to protect both the VFD and the motor. It doesn’t hurt anything, it just quits. What’s the biggest problem with backup generators many homeowners install? It’s inactivity. Any motor should be run at least twice a month to circu- late the lubricants, among other things. Since the hybrid gas-electric garden tractor can be used as a portable power source, it can be used as a backup gen- erator. In fact, it can be plugged into grid power which will keep the tractor battery fully charged. When the power goes off, the hybrid gas-electric garden tractor can start automatically and “feed” power to the house until the power comes back on. Britt Britt Storkson may be contacted via e-mail at admin@ worldwidedrillingresource.com 41 WorldWide Drilling Resource ® AUGUST 2013 4< /*2'3* "& > > > > ,'< ? /2+ '6* /3+6 /3+6 ')1/3- " " !8=2+ /7843 4* 4* ')1/3- !+8 5)7 !8'3*'6* $'2:+ 9((+6 6':+2 $'2:+ 9((+6 !+'87 9((+6 $'2:+ 37+687 #6+8.'3+ $'2:+ 37+687 $'2:+ !56/3- ! ! $'2:+ 4:+6 '71+8 ? !;/:+2 ')1/3- ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 ? !+6/+7 < /3+6 < /3+6 < /3+6 < /3+6 < /3+6 6/)+7 !9(0+)8 "4 .'3-+ %/8.498 48/)+ !@ @ < < < < <