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Baldor 3-phase motor for RPC

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  • #31
    Do you hear the start contactor get energized and de-energized? Is power getting to the timer board?

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    • #32
      Originally posted by Mr Fixit View Post
      Fear,


      So the one thing that you can do is use the switch if it is as I describe, to energize the start contactor and then let go and it puts the system in the run mode and all is good.. This is if the system is low voltage. If these are 240v coils then the switch will need to be verified that it is rated for this voltage which from the gray cable I doubt it, but they do make it in 300v rating so maybe it is.



      TX
      Mr fixit for the family
      Chris
      I went and checked and those switches look like they were made to take anything you threw at them.

      Everything I'm looking at seems to say the control is all 240v single phase. I figured anything would step down to at least 120v for control circuits.

      I'm figuring a push/pull mushroom kill switch to break everything, and a start switch for the run contactors and a momentary push for the start contactors. I'm only worried if there was a power interruption and I don't notice then the RPC would stop turning, then when power resumes there would be single phase legs powered with no turning armature which could burn the caps or motor. I'm thinking a latching relay with a momentary start for run so a power interruption would kill power to the run contactors when power comes back on.

      Do they even make 240v latching relays? It almost looks like it's wired so the run contactors have a built-in latching feature. I can't make sense out of Schneider's online literature.
      Last edited by Fear; 05-11-2020, 08:56 PM.

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      • #33
        Originally posted by reggie_obe View Post
        Do you hear the start contactor get energized and de-energized? Is power getting to the timer board?
        It's built in a way that I have to pull the whole chassis apart to even see the contactors or timer board. I don't have enough length on my leads to get it to where I could spread it out under power.

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        • #34
          Does this make sense? Click image for larger version

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          • #35
            and a start switch for the run contactors and a momentary push for the start contactors. I'm only worried if there was a power interruption and I don't notice then the RPC would stop turning, then when power resumes there would be single phase legs powered with no turning armature which could burn the caps or motor. I'm thinking a latching relay with a momentary start for run so a power interruption would kill power to the run contactors when power comes back on.
            I don't know all the details, but the contactor is started with a momentary NO, held open by itself, then broken by the NC. There is no concern about power failure, as the contactor will break when power is lost.
            21" Royersford Excelsior CamelBack Drillpress Restoration
            1943 Sidney 16x54 Lathe Restoration

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            • #36
              I removed the timer board and wired in a momentary NO straight to the start contactor. I start the run contactors, then the start contactor and there's no change. The motor's output shaft just twitches back and forth. I try again spinning the output shaft by had and then hit each start and it starts spinning faster and faster and sounding good, but the second I release the starter contactor it slows down. I tried to see readings but it kicked the 125amp single phase input breaker before I could see. I reversed the input leads but it didn't change it. I got my wife to snap the picture of readings while I had it spinning good with the start contactor engaged.
              The first picture is the single phase input voltage, second picture is the phases as read at the 3ph sub panel after the RPC.

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              • #37
                Are you sure the start contactor is actually closing? Disconnect the string of start caps and wire 2 110V bulbs in series where the caps were attached. Disconnect motor temporarily, Hit your RPC Power button, then hold your Start button, if bulbs aren't bright or flicker or dark, you've got a problem.

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                • #38
                  AFAIK one of the phases should be the same as the line voltage, which you show as 247 VAC, but the output voltage L1-L2 is only 211 VAC and the other phases are only about 1/2 that. This means that there is essentially no phase shift on the third leg, and the motor windings are acting as a voltage divider. Find out why L1-L2 is so much lower than line voltage, and then check the capacitors to see if they are any good. You might be able to simply wire the run capacitors to the third leg, and that may be enough to start the motor, and certainly should run it once spinning. A quick capacitor check would be to connect it to a 9V battery with a 100k resistor across the terminals. Measure the time for the voltage to drop to 3 volts, then use the formula TC=R*C, or in this case C=T/0.1. 10 seconds would be 100 uF. This is just a rough check, maybe good to 20% error, but enough to see if they are not shorted or open circuit or very leaky.
                  http://pauleschoen.com/pix/PM08_P76_P54.png
                  Paul , P S Technology, Inc. and MrTibbs
                  USA Maryland 21030

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                  • #39
                    Originally posted by PStechPaul View Post
                    Find out why L1-L2 is so much lower than line voltage, and then check the capacitors to see if they are any good. You might be able to simply wire the run capacitors to the third leg, and that may be enough to start the motor, and certainly should run it once spinning..
                    I just replaced the start caps. All brand new American-made. I'll get some lights and check that. The voltage and amps were likely still settling. I only had a few seconds to snap pictures and hit stop before popping the breaker.


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                    • #40
                      If the meter that's part of the RPC is reading 211 from L1-L2, where is the DMM attached that it reads 247?

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                      • #41
                        Originally posted by reggie_obe View Post
                        If the meter that's part of the RPC is reading 211 from L1-L2, where is the DMM attached that it reads 247?
                        I hope you're joking.

                        The "247v" is my Fluke meter to each of the L1/L2 input bars. The three digital readouts are ones that I installed in a plastic box on the wall I got from Lowe's.

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                        • #42
                          Originally posted by Fear View Post

                          I hope you're joking.

                          The "247v" is my Fluke meter to each of the L1/L2 input bars. The three digital readouts are ones that I installed in a plastic box on the wall I got from Lowe's.
                          Not joking at all. Trying to make sense of the voltage readings before you get led astray. L1 to L2 input voltage on the fluke is acceptable. The reading on our L1-L2 digital meter is greatly different, where is it connected? Is it on the output side of your incoming power contactor?

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                          • #43
                            There is something messed up for sure.

                            Problem #1 is that the motor will not keep running when you take it off the start. For the moment, focus on that. The rest of it can be checked later.

                            A wise car repair shop owner once gave me a great piece of advice.... "When a problem just does not make sense, FIX WHAT YOU KNOW IS WRONG". Much of the time, that will fix other things as well.

                            What we know is wrong, is that the motor starts, but will not stay running, per your post #36. Nothing works if the motor will not run, you need to fix that first.

                            So.... First thing is to triple check the wiring. In fact, you should trace out the wiring and develop a schematic of the unit. Since you are not using the timer, there is not much to trace out, really. Just contactors, terminal strips and capacitors, with a couple push button switches.

                            You need the schematic for the power, and the schematic for the control circuit.

                            The idler should run fine on single phase coming in two wires. It should pull about maybe half of full load current, a bit more than it would if running on 3 phase.

                            Since it does not, you need to determine if it is getting voltage. At start, the main contactor should close and latch, and the contactor for the start capacitors should close also, but only for as long as the button is held. (at shutdown, the stop button should open the main contactor).

                            During the start, there should be NO LOAD on the output of the converter. That is normally easy, since the loads are left "off".

                            If the main contactor does not latch, obviously the idler will stop. If that happens, then you need to check the control wiring. There should be an "aux" contact on the main contactor to "latch" it closed (often called "sealing").

                            Really, much may be made clear by making the schematic of the converter.
                            Last edited by J Tiers; 05-14-2020, 11:08 PM.
                            1601

                            Keep eye on ball.
                            Hashim Khan

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                            • #44
                              I drew this three times and still put the caps in the wrong place. What's a good Mac-friendly schematic drawing program (cheap-free)?

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                              • #45
                                Here are some choices, but I use Win10 and haven't tried any of these (although I evaluated Eagle many years ago):

                                https://machow2.com/electrical-design-software-mac/

                                Comparison of many EDA platforms:

                                https://en.wikipedia.org/wiki/Compar...f_EDA_software

                                I see that KICAD works on MAC. And so does LTSpice, which can be used for schematics as well as simulations. I use that quite a lot, as you may have seen here.

                                http://pauleschoen.com/pix/PM08_P76_P54.png
                                Paul , P S Technology, Inc. and MrTibbs
                                USA Maryland 21030

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