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Baldor 3-phase motor for RPC

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  • #46
    The simple way is to draw it on paper and take a pic of it.
    1601

    Keep eye on ball.
    Hashim Khan

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    • #47
      This was a fun post. I have an Art designed 5hp3ph converter. Works day in and day out. Small, 12"x10" motor giving my bridgeport and any thing else it wanted.

      An it is quiet. I had to remove the end of the shaft. Nice lil package.

      Dont ask whats in the box. Motor alone does not make good 3ph.

      I could show you the contents of the 10x14" grey box with Art's permission. Until then you just have to make it.

      Wish u all the best. Remember. Art was on the internet in the 80-90s.

      He was the Father of home made RPC!! JR
      My old yahoo group. Bridgeport Mill Group

      https://groups.yahoo.com/neo/groups/...port_mill/info

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      • #48
        I drew the whole schematic out on one sheet of paper only to realize I put the capacitors in the wrong place and I was not drawing that whole damn thing out again.

        I put 240vac to the control side of the contactors after stripping all connections to one side and I checked resistance across all 12 points of the 3 run contactors (4 sets of contacts each) and they all ohmmed out perfect. I checked the resistance on all the capacitors and they all matched, so I don't know the spec but if they all show the same reading, I think they're good.

        I realized while checking all my pictures to make sure I reconnected all the wires right that when I got it the wires were blown off many of the caps, so I asked American Rotary to send a schematic. The best they could do was a picture of an old panel they had in stock that was the same age and model. When I rewired it I saw where someone had removed the capacitors from between L2 and L3 and taped the wire off. They then installed jumpers to add those caps to the caps between L1 and L3. Kind of a Bandaid for not having enough run caps from the factory. So I ordered 5 more caps from Ebay. So I now wired it so where it had 2 caps between L2 and L3, it now has 4 caps. And where it had 4 caps between L1 and L3 it now has 7.

        I couldn't get the video to load, but I still have to spin the output by hand before hitting start but now it runs on it's own for a few seconds before tripping the breaker.

        The voltages while running show 210vac between L1&L2 (the two non-fake leg feeds), 122vac between L3&L1 and 98vac between L2&L3.

        I'm happy it runs on it's own now, but it's far from fixed.

        Is there a chance I'm not engaging the start contactor long enough to get it to proper speed?
        Last edited by Fear; 06-06-2020, 10:14 PM.

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        • #49
          You shouldn't need capacitors across L1 and L2, except maybe for PF correction. Having seven capacitors there may give enough phase shift to negate the phase shift effect of the capacitors across L2 and L3. There should not be any capacitors between L1 and L3. Your voltages 122 VAC and 98 VAC add up to 220 VAC which is just slightly more than the 210 VAC input on L1 and L2, and that means there is only a tiny bit of phase shift, far too little to approximate a three phase supply. It seems like the voltage on the manufactured leg L3 is just from the two motor windings acting as a voltage divider.

          Can you try using a small three phase motor instead of the big Baldor, to see if it produces a more reasonable phase shift? Or even check the voltages without the motor, although it would be better with some load, such as three incandescent lamps or heaters wired in star or delta? Or maybe you can find a Three Phase Light Bulb?!
          http://pauleschoen.com/pix/PM08_P76_P54.png
          Paul , P S Technology, Inc. and MrTibbs
          USA Maryland 21030

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          • #50
            Originally posted by PStechPaul View Post
            You shouldn't need capacitors across L1 and L2, except maybe for PF correction. Having seven capacitors there may give enough phase shift to negate the phase shift effect of the capacitors across L2 and L3. There should not be any capacitors between L1 and L3. Your voltages 122 VAC and 98 VAC add up to 220 VAC which is just slightly more than the 210 VAC input on L1 and L2, and that means there is only a tiny bit of phase shift, far too little to approximate a three phase supply. It seems like the voltage on the manufactured leg L3 is just from the two motor windings acting as a voltage divider.

            Can you try using a small three phase motor instead of the big Baldor, to see if it produces a more reasonable phase shift? Or even check the voltages without the motor, although it would be better with some load, such as three incandescent lamps or heaters wired in star or delta? Or maybe you can find a Three Phase Light Bulb?!
            That was a typo. The 3ph bars are arranged "1, 3, 2" with the fake leg being the middle bar making it easier to arrange components.

            The plan was 4 caps between L2&L3 and 7 caps between L1&L3. I realized looking at the picture I screwed up and have 2 caps between L2&L3 and 10 caps between L1&L3 (whoops!). I'll rearrange and see if it helps.

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            • #51
              Alright. I switched jumpers. Now the split is 8 caps between L1&L3 and 4 caps between L2&L3.

              When it runs I get 211vac between L1&L2, 105vac between L2&L3 and 113vac between L1&L3.

              It still trips the 125amp breaker.

              There might not be any problem other than I just need to up my breaker size to 150amps. But the last owner said he ran 125amp and American Rotary said that was enough for 40hp. I'm cool with getting a bigger breaker, but it's popping after running a few seconds. The motor should draw most at start-up or when the 3ph side is under load. Running unloaded should be the least draw on the single phase side in my mind.
              Last edited by Fear; 06-06-2020, 10:50 PM.

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              • #52
                Try removing all four capacitors from L2 and L3.
                http://pauleschoen.com/pix/PM08_P76_P54.png
                Paul , P S Technology, Inc. and MrTibbs
                USA Maryland 21030

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                • #53
                  The voltages appear to show NO activity of the idler motor at all. Are you certain it is connected where you think it is?

                  "Capacitor" is not a "value", it is a general description. The capacitance values of the parts are needed to get an idea of what is going on.

                  THERE IS NO POINT TO THIS THREAD WITHOUT A WIRING DIAGRAM.....All is made clear by accurate wiring diagrams and schematics, but nothing much is clear from descriptions in typed words.
                  Last edited by J Tiers; 06-06-2020, 11:39 PM.
                  1601

                  Keep eye on ball.
                  Hashim Khan

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                  • #54
                    Originally posted by PStechPaul View Post
                    Try removing all four capacitors from L2 and L3.
                    Why wouldn't you want any capacitance between 2 and 3?
                    21" Royersford Excelsior CamelBack Drillpress Restoration
                    1943 Sidney 16x54 Lathe Restoration

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                    • #55
                      Originally posted by J Tiers View Post
                      The voltages appear to show NO activity of the idler motor at all.
                      THERE IS NO POINT TO THIS THREAD WITHOUT A WIRING DIAGRAM.....All is made clear by accurate wiring diagrams and schematics, but nothing much is clear from descriptions in typed words.
                      Here's the schematic. The caps are in the wrong place but I've been adjusting the caps around so it doesn't seem to matter where they are on here beyond where I say they are at the present time.

                      What makes you think there's no activity from the motor? The damn thing is spinning and it's the only draw on the circuit that is popping a 125amp breaker.
                      Attached Files

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                      • #56
                        Hard to tell for sure, but it looks like the start capacitors go from T1 to T3, while there are five run capacitors from T1 to T2, and two from T2 to T3. L1 goes to T1 through a 4 pole contactor and 2 poles of another contactor. L2 goes to T2 through a 4 pole contactor and two other poles of another contactor. So it looks like the start capacitors will try to spin the motor in one direction, while two of the run capacitors will (mostly) try to spin it the other way. The capacitors from T1 to T2 are across the supply line L1 and L2, and will not contribute to phase shifting on the manufactured leg T3. But they will draw extra current. A total of 500 microfarads (uF not mF) will have a reactance of 5.3 ohms at 60 Hz, With a 210 VAC input, that will be 40 amps of current. Since the motor is inductive, it is possible that there could be some LC resonance shenanigans going on, which can build up to a very high voltage and insulation breakdown which could trip the breaker.

                        BTW, I suggested removing the capacitors from L2 to L3 and leaving them on L1 to L3, because they subtract from the phase shift.
                        http://pauleschoen.com/pix/PM08_P76_P54.png
                        Paul , P S Technology, Inc. and MrTibbs
                        USA Maryland 21030

                        Comment


                        • #57
                          I think ther is no activity from the motor because if there were, the motor should be putting out a reasonable voltage on the generated ("fake") output wire. But since the voltages are low, and add up only to approximately the incoming voltage, then the motor does not seem to be properly connected.

                          There is also the matter of all those capacitors across the input lines. They are doing nothing particularly useful and only draw more current. (they probably are overcompensating for power factor)
                          1601

                          Keep eye on ball.
                          Hashim Khan

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                          • #58
                            There is a picture in this ad for a 40HP phase converter that shows the inside of the panel. I have no idea if it is the same as the one you have but might give an idea of the cap wiring.

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                            • #59
                              Originally posted by J Tiers View Post
                              I think ther is no activity from the motor because if there were, the motor should be putting out a reasonable voltage on the generated ("fake") output wire. But since the voltages are low, and add up only to approximately the incoming voltage, then the motor does not seem to be properly connected.

                              There is also the matter of all those capacitors across the input lines. They are doing nothing particularly useful and only draw more current. (they probably are overcompensating for power factor)
                              I had tried to make it clear that the reason I didn't share this schematic earlier is because there are no capacitors across input voltages, that was my mistake and I didn't want to redraw this whole thing over a couple of mistakes. There's three times as much wiring and components than what I've seen in other RPC schematics.

                              The run caps are set with 2 between L2&L3 and 5 between L1&L3. I just really didn't want to draw this whole thing again over that.
                              Last edited by Fear; 06-07-2020, 10:40 AM.

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                              • #60
                                OK You DID say that, but it was a while back and I thought it was fixed on schematic, I guess. (Pro tip: Use pencil for schematics when tracing circuits)

                                That does not affect the comment, however. If the motor is turning under power, AND THE WINDINGS ARE GOOD, there is no alternative, it WILL produce "approximately" the same voltage across 1-2, 2-3 and 1-3 (3 is generated line), there is no choice, it is "baked-into" the way the motor works.

                                Now, if there is a very heavy load on , say, 1-3, that may draw down the voltage and also pull a very large current.

                                The first thing I would suggest (and I think I may already have done so) is to disconnect ALL the "run" capacitors. They are NOT required for generating voltage, they are for "tuning" it, if needed. So DISCONNECT the 2 and the other 5. Make sure the wires are not touching anything they should not.

                                Make sure all loads of any sort are DISCONNECTED from the generated line output.

                                NOW test the thing again. If all it correct, you SHOULD have the idler start and run, the start capacitors should disconnect, and you should have approximately the same voltage across 1-2, 2-3, and 1-3. Probably the 2-3 and 1-3 will be a little lower than the input.

                                If you do not get that result, but the breaker holds check all the motor connections.

                                If you still get the heavy current and breaker opening, check for wrong connections in wiring, if none, the motor may have a problem, or it may be connected wrong (reversed coil)

                                The 40 HP motor will pull a bit over 100A if under full load, and on idle, it may pull as much as 40 or 50 A. I would NOT expect it to pull much over that just running with no run capacitors and no load.

                                Power factor capacitors might help by reducing the no-load draw, but leave that until it is all working OK otherwise


                                Last edited by J Tiers; 06-07-2020, 01:29 PM.
                                1601

                                Keep eye on ball.
                                Hashim Khan

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