Wednesday, 16 October 2013

Day 5

Its been a two weeks worth of school holidays, with two assignments to complete and project work was suppose to be on the home stretch, tying up the loose ends, hoping to finish our projects today. Hooking up to the busbar and happily providing power to the classroom and fingers crossed- the grid. This wasn't going to be the case, we encounter more hiccups and set backs. Our hydro project went from a pleasing 30ish volts down to the mid teens, we check the varible speed drive, phase rotation, hose placement and anything else we could think off, is it the fact that each day we set up, we have to break it down and move it at the end of the day? No- if we can get results once, we must be able to get them again. Along with the hydro work we managed to get some work done on the second wind turbine connecting it to the three phase full wave bridge rectifier we salvaged out of the first wind turbine unit, the unit we reconditioned at the start of this project, as well as running cable to prep for joining the second wind unit to the bus. Circuit continuity tests were good, so were the preliminary voltage tests although inconsistent as the wind blows in gusts, not a nice steady flow, for each step forward we seem to find another hurdle. We are feeling the pressure as the big reveal is approaching fast and we still have a few bugs to iron out. Moving into our final days our approach is going to be positive with a sense of urgency, just keep working at a good steady pace, thinking and problem solving as we go.

Sunday, 29 September 2013

Day 4


-Set up the variable speed drive to increase frequency which will increase the speed of the motor to  increase our out put.

-Set up oscillicope to get a reading of our sinewave for our wind turbine.

  Today we've got the variable speed drive set up to improve the water pressure by increasing the frequency. We found 65 hertz worked best without overloading it. We started off getting 14v using the the large hose(20mm) as the down pipe onto the Pelton wheel and at a later stage we decided to replace the big hose with a smaller hose(15mm) allowing us to change the angle point on the Pelton wheel in doing so we managed to find the sweet spot for water to land on the wheel giving us an out put reaching 34v .
  Today it was not very windy so the wind turbine failed to give us an output of 12v. We need a constant 12v for the inverter to change it from dc-ac so we can check its sine wave on the oscilloscope, we hope to do this on a windy day before connecting to the buss.
Day 3

Goals:  Get hydro working at its optimum level.
            Connect wind turbine to busbar
            Solve the issue of stepping 12vDC to 24vDC for the wind output

  To achieve our goals today we need to finish the wind turbine. We decide to use a variac to increase the output. We also need to check the smoothness of the DC output wave by using an oscilloscope, to make sure it will be able to charge the batteries that are our busbar.

wind----> 3phase output ?vAC----> rectify to single phase 12vAC----> step up to 24vAC---> inverter DC output----> busbar

  Today was also the day we managed to spin the pelton wheel for the first time, by using a larger hose and altering the position of the hose input we managed to get 5volts AC. We need an output of 12volts. This was discussed at length and trialed a couple of ideas. A 3phase full wave rectifier was built using diode packs which also increased our output to around 11vDC, which is a step in the right direction. Bring on tomorrow. 


Day Two

A team meeting starts the day with safety and the daily goals being discussed.

Goals for the day - figure out how to open the wind turbine unit
                            - test wind turbines internal working and find faults
                            - have the turbine mounted and running
                            - start assembling hydro project

  We decide to split into two groups of two, with Mitch and Jordon focusing on the hydro project, Kane and Sam working on the wind. This division of work was a key aspect to a successful, productive day resulting in goals getting meet. We still came together at several crucial points of the day, to problem solve as a team to overcome some of the larger issues we encountered.
  Once the wind turbine unit had been cracked open we tested the windings, getting even readings across the three.We opened it up further to see previous modifications- three full wave rectifiers turning the 3 phase AC input into a DC single phase output. Faults were easy to see, the 2.5mm wire connecting the rectifiers had conductors snapped and dodgy terminations, we had a couple of options- use the same rectifiers replacing the wire and improving the connections, adding support to our new terminations by using strengthening putty. Replacing the three rectifiers with one three phase rectifier- at this stage our preferred option- we wanted to upgrade the unit, to improve it and make a worthwhile contribution.  We got our hands on 3 phase full wave rectifyier which answered our dreams. Assembly was straight forward and with our previous experience, it was up the pole- piece of cake.
  Our full attention was then on the hydro project, it was ready for it's test run with time up our sleeve. Our first run produced no water from the hose- our 3phase pump wasnt working- we swapped two phases over- we had water, but not enough pressure to move the pelton wheel.      


Day 1 on the job.


 The morning was used for the overall planning of the project, getting our heads around the different tasks involved, the sequencing of the tasks, our responsibilities involved around the co-ordination of the other teams accessing the busbar, which is an integral part of the class project, with all teams "plugging in". How to address these issues in the most efficient way, was a lengthy discussion between our four team members. 
  The first step after lunch was to assess the wind turbine- which meant assembly and testing. This was enough work to keep us busy  for an afternoon. Our preliminary tests were visual- checking the general condition of the turbine, looking for any obvious faults, it passed. Electrical tests were a little less conclusive, we knew circuit continuity was a problem, from our tests using the Ohm meter.We discussed the idea of disassembling the unit, checking the internal connections- insuring the terminations were ok and everything was fine.  We then tried to spin the blade to get a voltage reading, but then questioned  "how fast does it need to spin to get a reading of voltage produced. Could we do it by hand? Or did it need to be mounted up the pole working under more ideal conditions." We decide to erect the turbine to the top of the pole, under superb conditions to record sketchy voltage readings, fading in and out. Conclusive evidence that our initial prognosis was correct- poor circuit continuity. Slightly disheartened, we removed the turbine from the pole and finished the day knowing we have to backtrack, pulling apart the unit to check internal connections.
how a pelton wheel works

How Wind Turbines Generate Electricity