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Lockridge Device - Peter Lindemann

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  • Finally get a chance to take some pics of a comm setup that is very easy to put together and very adjustable. Like I said just mount them both on a shaft and jumper as many comm segments together as needed then connect the slip ring terminal to the segments jumpered together. HTH Wayne
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    • Field - Shunt / Series

      Thanks Mark - you are indeed correct - my motor is definitely series wound.

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      • Originally posted by emfimp View Post
        Thanks Mark - you are indeed correct - my motor is definitely series wound.
        My recollection from the DVD is we want to use a DC shunt motor (field coil in parallel). It seems to me a series-wound configuration would offer unnecessarily large resistance to current flow from the capacitor. To get maximum torque, we want maximum current.

        It might be worth exploring the idea of decoupling the field coils altogether, and run them on 12VDC, either commutated in parallel with the armature or just on all the time. Commutation might produce a bit more "kick" as the field coil current is switched off, similar to how an ignition coil works. 12VDC through the field coils would eliminate the need for rewinding for higher voltage or a resistor in series to limit the voltage.

        Comment


        • Ok I received and watched the video......

          If we need large motors like the ones in the video to get 300 watts then what kind of system would we need to get 3K watts.... or even 5K watts?

          My house uses way more than 300 watts.....

          Hopes and Dreams....

          Tj

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          • Ac Delco components ww2 era

            Here is a link to a free download of an AC Delco electrical manual from the ww2 era. Covers Starters, Generators and Ignition...very interesting. TM 9-1825a - Delco-Remy Electrical Repair Manual, WW2

            Bill H.

            Comment


            • Originally posted by Bill H View Post
              Here is a link to a free download of an AC Delco electrical manual from the ww2 era. Covers Starters, Generators and Ignition...very interesting. TM 9-1825a - Delco-Remy Electrical Repair Manual, WW2

              Bill H.
              Thanks for sharing that Bill H ! Very interesting indeed !
              ________
              Creole & Cajun Recipes
              Last edited by dragon; 05-11-2011, 11:11 AM.

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              • The commutator is almost complete, just lacking a spring system. I decided to take a few measurements on the frictional losses ( brushes, bearings, flywheel etc ) and found it to be quite high - much higher than I would consider good. Taking some measurements from the flywheel I ended up reading about 1.5 lbs on a 3.37 radius to start rotation. This would be a load of about .4 ft lbs continuous and at 3000 rpm were looking at mechanical losses of around 170 watts - not good.

                The motor alone runs 80 watts no load, with the flywheel it draws 110 watts until it's up to speed then falls to the original 80 watts but with the starter connected draws 180 watts. The starter motor may not be the best choice. Removing the brushes from the starter it seems to freewheel quite nicely, the brush drag is extreemly high.

                I'm going to look into some alternatives and start work on phase 2 of this project. I believe Peter's attraction motor to be a far better alternative to the starter motor.

                I'm going to need another week....
                ________
                StunningNika
                Last edited by dragon; 05-11-2011, 11:12 AM.

                Comment


                • Originally posted by phil.g View Post
                  My recollection from the DVD is we want to use a DC shunt motor (field coil in parallel). It seems to me a series-wound configuration would offer unnecessarily large resistance to current flow from the capacitor. To get maximum torque, we want maximum current.

                  It might be worth exploring the idea of decoupling the field coils altogether, and run them on 12VDC, either commutated in parallel with the armature or just on all the time. Commutation might produce a bit more "kick" as the field coil current is switched off, similar to how an ignition coil works. 12VDC through the field coils would eliminate the need for rewinding for higher voltage or a resistor in series to limit the voltage.

                  Good points Phil - Peter does recommend a shunt motor in the vid, & I'm not entirely sure why. The series wound (according to his 3 comparison graphs) shows a lot more torque available, compared to the shunt or permanent magnet motors. It is possible the armature winding method that Peter recommends is only available on shunt wound motors...

                  As far as the idea presented of rewinding the field coils (for a shunt motor specifically), I believe that the purpose of this is not because of the higher voltage input - we are running a lower duty cycle along with the higher voltage, so this ought to even out. (No smoke test danger here)

                  I believe the purpose of rewinding the field with more turns of higher gauge wire, or adding a resistor, is to lower the field strength, which will lower the back emf generated - thus increasing the available output power from the motor. (making it act more like a series wound)

                  I agree that we want maximum torque from the motor, & therefore maximum current is desirable. I do believe that whatever added resistance that may exist from a series motor configuration will not be significant, as Peter talks about the resistances from these motors being 1 ohm or lower. Wish I had mine here to measure...

                  Also, back to Peter's 3 torque/speed charts, the series motor again seems to demonstrate significantly more torque than the other two configs, demonstrating a real life advantage. Reality trumps everything, with the exception of the stock market & banks - there you'll find that money trumps reality...

                  Also one other specific about the motor I picked up - technically it is a split series motor. Basically there are 4 field poles - 2 in series with each other, and this pair in parallel with another 2 that are in series with each other. Then this whole assembly is wired in series with the armature. If one wanted to reduce the resistance of the motor further, one option would be to simply wire all 4 field poles in parallel with each other, then wire this assembly in series with the armature. Of course, as you have pointed out, there are far more options than this as well.

                  Love the discussions that are happening here!
                  Last edited by emfimp; 01-02-2011, 06:16 AM.

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                  • Anybody out there have one of those newer high efficiency furnaces? I'm told they have a dc motor in them, and that they are insanely cheap to operate, as far as the electricity consumed. (something like $50 per year, running them 24 hours a day, every day of the year)

                    It'd be neat to put a scope on one of these - they may encompass the very idea that we're all talking about on this thread. Torque enhancement off the shelf!
                    Last edited by emfimp; 01-02-2011, 06:34 AM.

                    Comment


                    • Emphimp

                      You might want to go back and study the 3 graphs again. The scales were not the same on all 3. Pick out different settings and compare them on all 3 graphs.

                      Mark

                      Comment


                      • Originally posted by emfimp View Post
                        Anybody out there have one of those newer high efficiency furnaces? I'm told they have a dc motor in them, and that they are insanely cheap to operate, as far as the electricity consumed. (something like $50 per year, running them 24 hours a day, every day of the year)

                        It'd be neat to put a scope on one of these - they may encompass the very idea that we're all talking about on this thread. Torque enhancement off the shelf!
                        I have a blower from one of the newer furnaces. It's 240VAC but the controller in the motor converts it to PWM DC for running in constant torque mode. I bought it for a (failed) air circulation issue in my home. It's runs at around 5 amps when a similarly sized induction squirrel cage blower motor would require around 10-12 amps. It uses less power but if you ran it 24/7 it alone would cost more than $50 a year. It'd likely be more than $50 every other month to run continuously. There is no industry supplied silver bullet when it comes to heating...

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                        • Originally posted by Mark View Post
                          emfimp

                          You might want to go back and study the 3 graphs again. The scales were not the same on all 3. Pick out different settings and compare them on all 3 graphs.

                          Mark
                          I'm not sure I follow, Mark. Yes, the scales are different, but the fact remains the series motor shows the highest available torque (as a percentage of the 100% rated torque) when back emf is the lowest. (which is when speed is close to zero) Did I miss something?

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                          • Thanks for the reply everwiser - it was worth a shot!

                            Comment


                            • Originally posted by emfimp View Post
                              I'm not sure I follow, Mark. Yes, the scales are different, but the fact remains the series motor shows the highest available torque (as a percentage of the 100% rated torque) when back emf is the lowest. (which is when speed is close to zero) Did I miss something?
                              Maybe I'm the one that missed it. The way I'm looking at it is that the motor will be running at somewhere between 50 to 80% of its rated speed and looking at the torque figure. I see how your looking at it. I guess only testing will tell the whole story.

                              Comment


                              • Originally posted by Mark View Post
                                Maybe I'm the one that missed it. The way I'm looking at it is that the motor will be running at somewhere between 50 to 80% of its rated speed and looking at the torque figure. I see how your looking at it. I guess only testing will tell the whole story.
                                Ah, I see - I guess I could have been more clear as to how I was looking at it. Sounds like you've already got it, but I'm looking at it like % back emf (like Peter was mentioning in the vid), instead of % speed. So we are trying to operate at 10 times (minimum) the rated voltage (120 volts+ for a 12 volt motor) - so for every one unit of bemf (12 volts, say) we have 9 units of energy creating torque for us (120 - 12 = 108v, 108 divided by 12 = 9)

                                Therefore we are running @ 10% bemf or lower (say 5 - 10%), so I am looking at the torque around the graph's 10 - 20% rated speed area. (remember that 100% rated speed is where the bemf = 50% of the rated input voltage, so 5 - 10% bemf happens around 10 - 20% rated speed)

                                Strange thing is that this should mean that the excess torque hits zero at about 200% of the rated speed. The series motor chart does this, but not the permanent magnet or shunt motor chart.

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