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  1. #21
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    When I opened the "phase a matic" box up that works the way my friend would like. (Always hooked up to power, load is switched on and off) I remember seeing saw 5 basic components. There was a 274-324uF start cap, a potential relay, a light bulb, a few resistors, and a little black box that I did not recognize. I will see if I can get a picture posted. The phase a matic works how he wants, and he would like to duplicate that functionality.

    So far, the best suggestion was here:
    Phase Converters

    The design is essentially the same as what we built with the addition of a dual primary transformer to generate the reference. I can do that, but the transformer specs aren't listed. Any suggestions on pursuing that design?

    Thanks,
    -Joe

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    Joe,
    You really have to get into the Phase-a-Matic box and draw out the circuit diagram.

    The link is using a regular control transformer.

    What Horsepower is the lathe motor? Then you can size a transformer accordingly.

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    Quote Originally Posted by 2Slow View Post
    So far, the best suggestion was here:
    Phase Converters

    The design is essentially the same as what we built with the addition of a dual primary transformer to generate the reference. I can do that, but the transformer specs aren't listed. Any suggestions on pursuing that design?

    Thanks,
    -Joe
    The transformer is a 120/240V primary, secondary voltage is immaterial as it is not used. The VA size has to be big enough to power the coil in the potential relay, 10VA or above should work.

    The transformer is used as a voltage divider, before the potential relay. This makes the generated voltage be double what the potential relay specs call for. The 6X555 relay specs can be found HERE.

    That would equate to about 340V on pickup, and 150V on drop out.

    SAF Ω

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    Quote Originally Posted by SAF View Post
    The transformer is a 120/240V primary, secondary voltage is immaterial as it is not used.
    "Not used" was my Phase-O-Matic. But y'all HAVE inspired me to make it useful again.

    I have two molded concrete pavers holding down a stack of poly mixing trays for DIY mortar and such so the wind dasn't carry them off.

    If I put the Phase-O-Matic atop the poly trays in their place, I can actually USE those two truant pavers, save $1.96 on pavers, plus Phase-O-Matic's weight @ $66/Ton at the landfill.

    Win-Win situation, yah?

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    Quote Originally Posted by SAF View Post
    You mean like this?
    Attachment 228001

    Attachment 228002

    SAF Ω
    That first one is close, they are making 90 degree 2 phase and using a transformer to shift it to 120 degrees. But it lacks the inductor (or saturable reactor, if you want it self regulating) to provide the voltage boost on the third leg, so you still have the annoyance of capacitive reactance causing phase imbalance.

    That second one seems to shift the 90 degree output of the capacitors to 120 degrees before driving the idler motor and should give a much better phase angle. (As you add capacitors to an RPC the phase angle from the third leg deviates from 120 degrees approaching 90)

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    Joe,
    A Lewus Converter is simple with a 3-Phase Wye-connected motor. The reactor improves the performance of a capacitor-only phase converter.

    L1 connects to T1
    L2 connects to T2
    Capacitor connects from T1 to T3
    Current balancing reactor connects from T2 to T3

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    Quote Originally Posted by rons View Post
    Joe,
    A Lewus Converter is simple.

    L1 connects to T1
    L2 connects to T2
    Capacitor connects from T1 to T3
    Reactor connects from T2 to T3
    Note that this will give you two phase with a 90 degree phase angle.

    You would need another transformer to get 120 degree three phase.

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    Quote Originally Posted by rons View Post
    We know what is wrong. What is your suggestion other than "Consider putting the load motor on-line before you power the system via the relay."
    Number 8 is not for that.
    If the setup works with the load motor on line when powering it up, then
    simply put the static converter in between the lathe contactor and the motor.
    This isn't a quantum computer.

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    Putting the phase converter after the contactors would work and should give my buddy all the functionality he wants. We kinda have it mounted in a location that would make it more messy to do so. Considering that, I think I am going to add the dual primary transformer and wire it like this link shows:

    Phase Converters



    2 Questions:

    1) Does this DP-241-5-24 transformer look up to the task:

    https://www.mouser.com/ProductDetail...XDvddizQ%3d%3d

    https://www.mouser.com/datasheet/2/643/241-1130952.pdf


    The Steveco 90-65 has very similar pick up and drop in V to the 6X555 relay so I think the transformer is the only part I will need to change.

    6X550
    Pick up 166 - 180
    Drop out 100 - 70


    Steveco 90-65
    Pick Up 171 - 184
    Drop out 90


    2) If all I am doing with the transformer is effectively changing the pick up and drop out voltages, would it make more sense to just use a different potential relay like a Steveco 90-68?
    Pick up 323 - 350
    Drop out 135

    STEVECO Relay,Potential - 4E657'|'9-68 - Grainger


    Thanks!
    -Joe

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    That potential relay you linked to is a discontinued item.

    I would dispense with the transformer, and try an adjustable potential relay.

    Supco APR5 adjustable from 130 to 370V, has a built in timer to cut the motor off if it dosen't start within 1.5 Sec. Does it start that quick with the Phase a Matic?

    Instruction Sheet



    SUPCO Relay,13-27 V - 4MG77'|'APR-5 - Grainger

    or, order online from the sister store

    Supco Relay, 13-27 V APR-5 | Zoro.com

    SAF Ω

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    A lot of trouble for copying a Phase-a-Matic static converter that sells at Walmart for approx $160. Couldn't believe it until I saw the add.

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    Those bastards sell converters? Sheesh.

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    SAF,

    I like the idea of an adjustable potential relay, but I think the built in timer might be a problem for this design. The lathe motor started in under a second with the phase a matic, so that isn't the issue with the timer, and it generally seems like a great protection idea for a design where the line is switched like a RPC. Since the line side is always hot and the load is switched in this design, I think the timer might open the potential relay when the lathe is sitting idle. I am not too worried about the Steveco potential relays being discontinued as they seem abundantly available new old stock on surplus sites.

    I started thinking about the static design where the guy added a diode and did not know why and the other with the transformer. Both of those were added to prevent the chatter problem I am observing. I think they both imply the pick up voltage is too low on the potential relay to prevent the chatter. I think the diode and the transformer were basically cutting the voltage down going to sensing pin #5.

    Rather than cut the voltage being sensed, why not raise the pickup voltage on the potential relay? Then I remembered that since the potential relays were only rated at 50 amps, and my 10HP RPC start caps could pull more, I had to decide if I should have the potential relay control a contactor , or just use two potential relays switching two sets of start caps separately to stay under the 50 amp rating. I went with the latter, and for a reason I can't remember (probably availability) I used one Steveco 90-65 and one Steveco 90-66. The 90-66 has a higher pick up voltage (208 - 239 vs 171 -184) So in my RPC half the start caps switch out a little sooner than the other half, but it has worked fine for years.

    I went back to my RPC tonight and disconnected the idler motor (load) and hit the start button to pull in the contactor that switches the line. like before, I heard a potential relay opening and closing, but this time I listened more closely and it was only one of them, not both. I disconnected them one at a time and confirmed that only one was chatering. Then I pulled the one that wasn't chattering out and it was the 90-66 (higher pick up voltage)

    I am going to go to my buddies house and swap out his 90-65 with my 90-66 and I think the chatter issue should go away on his static as it should basically be the same as my rotary without the idler load. I will then put his 90-65 in my RPC where I switch the line and I think everything should work. I will post an update for those that are interested.

    Thanks for the help so far.

    -Joe

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    The relay should cut out when the generated leg on the motor comes up to voltage. I suppose if the motor is not going fast enough, or has a load on it due to drive train components, it may not be able to finish accelerating to normal speed. In that case a higher voltage relay would delay the disconnection until the motor was going faster.

    But.... if the capacitor total value is at the high end of the range for that motor, it might be that the start caps are affecting the voltage generated.... you might try reducing the capacitance to the minimum that will reliably start the motor, and see if that helps.

    Quote Originally Posted by thermite View Post
    Is there anything that lot do NOT sell? .....
    Most anything I want..... Actually I do not know if they sell anything I want or not. I just do not darken the door of walmart so I never fond out.

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    JST,

    This thread is long and drifted a bit. The issue I was looking for help was a potential relay engaging and disengaging when the circuit is hooked to line voltage and the load is not hooked up.

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    Quote Originally Posted by 2Slow View Post
    JST,

    This thread is long and drifted a bit. The issue I was looking for help was a potential relay engaging and disengaging when the circuit is hooked to line voltage and the load is not hooked up.
    I think you got the best answers.

    Fan of statics or no, ANYWHERE yah needs a potential relay for "onesies" or "fewsies", adjustable it should be.

    A volume-production maker shipping a hundred a year to ten thousand-plus has what's needed "nailed down" can use fixed, save money AND reduce grief from out in the field from out-of-proper-range f**k-with.

    End-Luser doing ONE unit needs that adjustable feature to "go find" what works, rather than doing the math, taking measurements on "many"

    2 idlers worth.

    Real reason I like "idlers"? I'm a tad too lazy meself to mess with the extra complexity of a static.

    "Static" dasn't necessarily mean less acoustic noise, after all. Molested motors cannot always be trusted to keep a secret.



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    Quote Originally Posted by 2Slow View Post
    JST,

    This thread is long and drifted a bit. The issue I was looking for help was a potential relay engaging and disengaging when the circuit is hooked to line voltage and the load is not hooked up.

    Yes.... that is why it is chattering. The MOTOR is REQUIRED to avoid that. Yes, I DID assume you had the motor hooked up, because it will not work otherwise.

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    Ergh

    I spent some time at my buddies house, and the net result is that it still does not work, and I am frustrated.

    Things we tried:
    1) Replacing the Steveco 90-65 with a 90-66 (higher pickup voltage). This produced no discernable change. The potential relay stil clicked in and out when power was applied without a load at what seemed like the same frequency as the 90-65. Even though the potential relay clicks in and out constantly while in this configuration the lathe starts right up and all controls function properly when we engage the load with either the 90-65 or 90-66

    2) Frustrated about the chatter, we wired the phase converter after the lathe contactors, just before the motor. I was pretty confident this would work, but found a new issue. The potential relay no longer chattered (since it did not have power) and the lathe started right up. On the first attempt the lathe only ran forward and when we commanded reverse it didn't move. I then realized that when requesting reverse the contactors were swapping 2 ot the 3 wires to the motor and it swapped the non powered third phase into the input of the phase converter. No big deal, I moved the wires I tapped into for input power to the converter to the two terminals that switched and made sure the unswitched one was the one the phase converter output went to. Well now the chatter was gone, and the motor ran when forward or reverse was selected, however it always ran in the same direction... Looking at it and my diagram above it is the equivalent of swapping L1 and L2. If done after the converter this would change the rotation of the phase converter, however because this was at the input it not only swapped L1 & L2 at the motor, it effectively swapped Pin 1 and Pin 5 at the potential relay making the cap phase shift from the opposite reference., effectively undoing the first change and eliminating the ability to reverse the motor.

    3) The stupid phase a matic didn't have any of these issues, and works without being connected to the load, so I took it apart again.
    Inside the "phase a matic". The three terminals coming in from the right side of image are where the power connections are made. The top is L1, the center is the "third phase" for starting and the bottom is L2




    This is a view zoomed in a little. The system consists of a start capacitor (not in pic) a potential relay (p/n 74-502414), a 10w 500 ohm bleed resistor mounted on the potential relay, a light that comes on when the start cap is engaged connected to a small relay, and the sensing wire heading to pin 5 of the potential relay also going through both the small relay and a resistor (measured 15k ohms)




    This is a side view of the small relay,. Is it being used to sense when a load is connected and if so, how? Or is the potential relay not chattering because of the 15k ohm resistor in series =, or just a different pick up voltage?



    Frustrated,
    -Joe

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    Quote Originally Posted by 2Slow View Post
    Ergh
    ...
    Frustrated,
    -Joe
    Look on the bright side.

    You could be "satisfied" instead of "frustrated". All in under an hour. Have spent waaaaay more money.

    And have contracted Syphilis from a different sort of f****g-around.

    Mind, that IS still cheaper to cure than a static converter. But only if caught right away. Either one.

    Or so the grownups tell me.


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    Quote Originally Posted by JST View Post
    Yes.... that is why it is chattering. The MOTOR is REQUIRED to avoid that.
    Yep. Me too. Until I went back and read the first post.

    Relaxation.

    Oscillator.


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