When a pump kicks on, it does have a tendency to twist, and could possibly tangle up on another pump/line so there would have to be some method of separation?
I do like the idea of several separate setups, vs one huge one since it means simpler controls & electronics and if one does go out, you have the capacity of the others to hold you through.
One other option for the pumps to simplify things once you have achieved about the 65 Meter depth is a low voltage well pump available from Shurflo. http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200332019_200332019 Is just one vendor, posted because the specs are there.
The aspect of running well pumps from an efficient inverter system is a specific aspect of a book I have been working on that has taken the most time. the block diagram is easy and simple, but finding a simple low frequency oscilator with a sine wave output that has excellent stabillity.... With the discontinuation of availability of the "MAX038" chip, the solution is not so easy, and as time has been at a premium for me these days....
BUT the matter is not insurmountable, but would be very useful right now if I had finished this portion of my book. A solution may be ultimately as simple as/ or to be found in the schematic of one of the newer energy efficient frontload washing machines for concept- they use a 3 phase motor with PWM and a bit of variable frequency to ramp up the speed, and ramp it down. Having scrapped out one of mine already for mechanical failure, I may take a look at those parts for a better answer. Hysteresis losses (internal heat) are not as great when doing this with a three phase pump motor- Electrolux is using just PWM square wave as the drive method for their washing machines. I may be giving away part of my book here, but such schematics can be gleaned and adapted from simple motor control devices covered in Industrial electronics books.
From the sounds of what is available over in Afghanistan from this thread so far, they may have to build the circuitry they need, which is why I raise this.
At the simplest description I can think of- consider an AM transmitter where the "audio portion" is power MOSFETs firing, and the exciter is a 50Hz or 60 Hz sine wave. Variable from "0" to the rated frequency for ramping up and ramping down. Yes, this the dreaded "modified Sine wave" but remember your motor is immersed in water- constantly drawing away heat. You Class "D" audio amplifiers use this method for creating major amounts of audio power with less than logical heat sinking. The real killer of well pumps is the "on/off" nature of their service.30 KiloWatt Brats anyone?[ Parent ]
Within the inverter, you can regulate your low voltage " frequency signal" prior to waveshaping with 2 simple linear voltage regulators set up as is shown in the National Semiconductor Application sheet for the LM117/317 regulator. This allows you a means to trim your AC current potentials as needed. 30 KiloWatt Brats anyone?[ Parent ]
This can be done digitally on the cheap and can be very stable. Two options off the top of my head are (1) A microcontroller either with a D-A output or interfaced to one, (2) an EPROM (or EEPROM or OTPROM, whatever is cheapest) interfaced to an D-A converter and programmed with a sine pattern. Its address bus could be driven by a counter IC with timing from a 555-type timer. The microcontroller approach is probably the cheapest and lowest part count option.[ Parent ]
