Induction Generator Project Questions

Discussion in 'The Projects Forum' started by tmoncmm, Jul 24, 2014.

  1. tmoncmm

    Thread Starter New Member

    Jul 24, 2014
    1
    0
    Hello,
    I am experimenting with using an AC induction motor as a generator and have run in to a few problems. I have read through many posts about this topic on the forum here, but I have some specific questions about my project that I can’t seem to find any clear answers to.
    First is the motor I’m trying to use. The motor is from an old Xerox copier. The sticker that lists the specifications is faded so much that most of it can’t be read. What can be read says that it is a synchronous motor, single phase at 60Hz and draws .65 amps.
    Plugging the motor into the wall and using a tachometer confirms that it runs at 1800 RPMs exactly and using a meter that it draws .67 amps at 120VAC at no load.
    It has a 6uF starting(?) capacitor and two input power leads.
    Using formulas from http://www.reliance.com/mtr/flaclcmn.htm , I am pretty confident that I have most of the other specifications figured out and have listed them below…
    Input Voltage: 120VAC
    No load current: .67 Amps
    Operating Frequency: 60Hz
    RPM: 1800
    Poles: 4
    Horse Power: .07
    Torque @1800RPM: .204 ft-lb.
    What I’m not absolutely sure about are the last two calculations for HP and torque. By using the info I had I think I calculated them correctly. I was able to reverse the formulas and use all the figures in different formulas with the same results.
    So my first question is; do the values I have calculated appear correct?
    My second question has to do with the capacitor on the motor. If I disconnect it and try to run the motor on line current, it does start and run but the start is noticeably rougher and slower.
    From reading on other pages, mainly http://www.qsl.net/ns8o/Induction_Generator.html and http://www.redrok.com/cimtext.pdf , I know that another capacitor is required in parallel to allow the motor to start generating. I purchased 5 30uF running capacitors on line, but because of a shipping error I only received 1. The company is supposed to be sending the other 4. I got 5 instead of 1 because one of the other problems I have run into is that no one gives a clear answer as to capacitor values for a given motor and load. I figured I could start with 1 and then parallel more until I reach the desired result.
    My question about the capacitor that is already on the motor is what to do with it. By spinning the motor with a drill, I was able to get about 2 VAC out of it as is. If I add the 30uF capacitor I bought in parallel with the input leads, I can now get about 30 VAC out of it. If I disconnect the 6uF capacitor, I get nothing, if I short its leads I still get nothing.
    The real problem is I’m not sure how it is connected so I’m not sure how to remove it and still have a working generator.
    A couple other things that I need some clarification on are…
    To get the above mentioned 30 VAC out of the motor, I have to run it at around 2300 RPMs before it will start to generate. I can feel a slight catch when it starts to generate, before that it does nothing.
    I’m only getting 30 VAC out of it even at well above it’s rated speed.
    I am assuming that the reason for the above is not enough capacitance. Anyone care to weigh in on that?
    I can post pictures of the motor if that would help.
    Sorry for the long post.
    Any help would be much appreciated.
     
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