Body
MickOddly enough, I had the very best luck with an incredibly small inverter that was over twenty years old.It was a Statpower made in Burnaby British Columbia, and only 125 watts.It was the unit that without bells, buzzers, or breakers, drove ten big permanent magnet motors at full speed, and power using Doug's bridge rectifier idea of parallel connecting a whole chain of these motors each with the rectifier AC legs down to the brush wires of the motor before it, in a line, in my case, of ten motors.I started feeding the 125 watt inverter into a 5 amp Variac, set at 35 volts.There was a progressive increase in voltage through the ten motors as one measured along the line of motors, until at the last one, it was about 93 volts.As you know, when you increase the voltage to these DC motors, you increase the speed.Well what about power? This was a question I asked myself.One of the motors, in about the middle of the line, happened to have a vee belt pulley on it, so I took yet another motor, and ran it as a generator off this randomly picked motor.The nice thing about a generator is that you can load it up, which I did. I think I remember it was 7.5 amps, or there about.All this time number 10, at 93 volts, was screaming away, unaffected in speed, or, I presume, power.
On one run, number 10 did a flip off the end of the bench with switch on.This knocked a field magnet loose, which required a take apart, and the magnet crazy glue thing.All in all, I found it interesting that ten big DC motors could be run from one 125 watt inverter that was only connected to a single 5 amp 12 volt lead acid battery. The motors were running for over a half hour, with no apparent slow down, or lack of power. The torque on anyone of them, as full as these motors normally deliver, which is quite considerable.I do think I might redo this experiment yet again.I blew a transistor, carelessly, on that Statpower, doing a complerely different experiment.I find the new inverters sold at Canadian Tire crap. They twitch, and beep, using any excuse for not running, using their smart little logic, rather than stoically delivering, until they explode, and burn.Cheers Warren
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On Sat, Feb 24, 2018 at 1:12 AM, [email protected] [EVGRAY]<[email protected]> wrote:
Warren,
I will have to take another look for surplus around here, don't think there is much of that within 250 miles.
There is a metal recycling place that sometimes rarely has these but they usually try for more than 20 bucks.
Ah the magic of large cities and dumpster diving!
I do keep my eyes out for curbside motorized excercise equipment like treadmills and such.
By the way I picked up a cheap Chinese inverter 220 3000 watt, so probably good for 1000 watts near full duty. Would not trust it as is, they were too cheap to use micas to seperate the fets from the heat sinks and used little silicon tubes cut to 3/4 inch over each piece of silicon. Of course no theremal paste, does not bode well for future use.
Anyhow the circuit is quite handy as it has two TL494's and four transformers.
Have you had a look at all one can do with a 494?
It's very fast 500ns, very hard switching with a wide frequency response determined by either an outside triangle pulse like a signal gen or it's own internal oscillator and an R/C like a 555 or another 494 it slaves to. A wide frequency range and voltage adjustable duty cycle by how much DC one of the pins sees. There are two driver sections that run parallel or push pull, one to drive fets right at their gates and a flip flop that runs at either 50 or 60 cycles to drive something else like SCR's to switch the whatever one does with the first section to square wave AC.
I wish the last part flip flop was variable too but I think it's programmed at 50 or 60hz but the first part is still there to toy with.
This inverter is called modified sine but there is nothing sine about it, super hard square edges. Of course one could add the filters and such to get a better representation of a sine but otherwise this thing can be hacked into 2 channels of push pull variable frequency coil pulser/drivers.I think the frequency is good from around 1k to 300k and can be driven right from a function generator or two.
Anyone here hacked a 494 while still inside a cheap inverter to pull variable frequency energy before the last FWB? #yiv3855261779 #yiv3855261779 -- #yiv3855261779ygrp-mkp {border:1px solid #d8d8d8;font-family:Arial;margin:10px 0;padding:0 10px;}#yiv3855261779 #yiv3855261779ygrp-mkp hr {border:1px solid #d8d8d8;}#yiv3855261779 #yiv3855261779ygrp-mkp #yiv3855261779hd {color:#628c2a;font-size:85%;font-weight:700;line-height:122%;margin:10px 0;}#yiv3855261779 #yiv3855261779ygrp-mkp #yiv3855261779ads {margin-bottom:10px;}#yiv3855261779 #yiv3855261779ygrp-mkp .yiv3855261779ad {padding:0 0;}#yiv3855261779 #yiv3855261779ygrp-mkp .yiv3855261779ad p {margin:0;}#yiv3855261779 #yiv3855261779ygrp-mkp .yiv3855261779ad a {color:#0000ff;text-decoration:none;}#yiv3855261779 #yiv3855261779ygrp-sponsor #yiv3855261779ygrp-lc {font-family:Arial;}#yiv3855261779 #yiv3855261779ygrp-sponsor #yiv3855261779ygrp-lc #yiv3855261779hd {margin:10px 0px;font-weight:700;font-size:78%;line-height:122%;}#yiv3855261779 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