These caps arent polarised , I guesss the only way they could be electrolytic is if they are in fact two caps like non polarised electro's . I did see a used one open from the end ,does look like paper/foil ,but hard to tell without unwinding and checking the foils ,two foils would suggest foilpaper ,three might suggest electrolytic . The black bakelite cased ones do have a vent very much like an electrolytic , the white cased ones are normally expoxied around the terminals .
I just browser searched , yes Prr your right ,the black cased are non polar aluminum electrolytic motor start caps , designed for intermittant use . Foil motor run would inevitably be larger size , 50-70uf would be more normal values.
Another avenue I'm needing to learn about is VFD's , or variable frequency ac drives , these are providing more and more economic speed/ torque control of ac motors ,and all the parameters can be easily tweaked over cat 5 if nessesary .
I may end up trying a VFD myself to speed control the synchronous motor in my watkins copicat ,Ive been messing around with dc motors on it for a while without much success ,so maybe I'll return to the original mains motor with a mini Chinese VFD .
I was also wondering how a VFD might do on reel to reel tape recorders to control the capstan motor speed .
The boss also asked about designing a moblie motor test jig , basically a frame with a motor mount ,coupled to a generator with resistive braking and fan cooling , which also incorporates strain sensors to plot torque rpm and vibration , could be VFD powered , a report with graphs could then be produced on-site ,and allow customers and our road bound service guys better evaluate motors and also catch impending fault conditions premptively . Tying in all the sensors and control voltages into a small microprocessor so it was totally self contained would be nice , but a small open source program on a laptop or tablet to run a test sequence on the VFD , integrate the data from sensors, and compile a performance report would be an incredibly usefull tool , such things do exist ,but usually they are proprietary systems costing tens of thousands of dollars .
Of course it probably could be made even simpler by having the VFD cycle through a preset test sequence , while the tech guy simply fills in values off the instruments on the tablet , but a totally automated testing unit in the back of the van would give the customer ,where down time is money ,especially if its unschedualed ,great reassurance everything is running 'tickety boo' and help give a real professional feel to our side of the bargain . I did contact a company in the US already ,they do dyno's mainly to measure Hp in V8's, that most indulgent of American obsessions , they have nicely engineered dynos with all the sensors embedded ,bolt it up , plug it in to the proprietary software and bang you've got all your gauges and dials up on screen , I did ask about integration of their sensors into thrid party or open source , and I got the impression I was being a bit of a spoil sport , I didnt press them on if they would sell me the hardware without the software ,yet
They are very willing to help though , so I'll contact them back this week .
So I guess tomorrow its gloves off and hack out the details with the boss ,Im happy enough on a starters rate while learning to bust up motors on the shop floor ,but I think the electronic tech side of things might deserve a better hourly rate , always a bit of poker facing going on in these situations . One of lads last week had to do a convair belt motor as used in the check out at your local supermarket , about 2 liters of snot green industrial lube poured out after gentle heating with Oxy/Acetylene torch ,and a belt of a large alloy mallet , theres nothing polite about this kind of work ,you dont know what kinda of shite such as PCBs have been added to the oils in 'sealed' systems . Another concern is being a smoker in a workplace of this kind ,bad residues on the hands can end up being smoked ,unless you wash very carefully , its rubber gloves for me from now on on the shop floor , and I'll even wash the crap residue left by the gloves off before I go on smoke break . Even still its a really dirty job and I want to be sure Im taking every precaution I need to to protect my health .
