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  1. JST

    15 hp RPC struggles to start 7.5 hp 3 phase air compressor - add cap?

    Easy enough. But if the utility is drooping, the lights will show it, different branch circuit or not. Basically, since the setup runs the compressor OK with added "idlers" in the form of machines "idling", that is a very positive indication that there is no issue aside from a sagging...
  2. JST

    15 hp RPC struggles to start 7.5 hp 3 phase air compressor - add cap?

    If you have lights in your shop, you have effectively already done the experiment. If the air compressor is drawing down the line, you should be seeing the lights dim, or some may even blink off. A drop in voltage sufficient to stall the compressor would be significant, and should be easily...
  3. JST

    15 hp RPC struggles to start 7.5 hp 3 phase air compressor - add cap?

    Missed this the first time through..... The RPC is "undersized" for the demand. You knew that, but that sentence proves it. You provbably know the rest of this also, but it may as well be stated. OK... "undersized" has details. The RPC can run that motor fine.... and it is significantly...
  4. JST

    15 hp RPC struggles to start 7.5 hp 3 phase air compressor - add cap?

    Yeah that is straightforward, and as you suggest, less screwing around. I have a small lab type pump that I plan to use for general 50 psi or so air around the "small work" part of the shop, and it won't start against any load. The unloader I have is not quite sized correctly, I may go with...
  5. JST

    15 hp RPC struggles to start 7.5 hp 3 phase air compressor - add cap?

    This is really not an issue for more capacitors. The capacitors can only do so much in terms of voltage boosting, and then adding more becomes counterproductive, actually adding a current draw to the generated leg. The centrifugal unloader should be good, it ought to delay closing until a...
  6. JST

    Rotary phase converter

    Normally higher at no load due to the common use of "balance" capacitors to raise the voltage. Also because the back EMF is the highest under no load, since the rpm is highest then. Having it a bit high at no load makes it more likely to be close to OK when it sags under load.
  7. JST

    Logan model 200 lathe compatible with a south bend worm gear apron?

    What you want is the Logan "Automatic Apron". Those, with compatible carriages, are available on ebay sometimes. You may need a QCGB and different leadscrew brackets, if you don't have them, as the apron is farther out than the plain one, IIRC.
  8. JST

    Rotary phase converter

    There are details...... Plain rectified loads draw short bursts of high current. That is exactly what the generated leg is not at all good at, and it will tend to contribute less charge to the power supply, acting like a low phase (which it may really be). (rectified loads with a power...
  9. JST

    Rotary phase converter

    Phase from an RPC is fine, but voltages from an RPC are different by around 6 to 10 percent You can correct that for motors, but rectified loads are more of a problem, and most CNC will have substantial rectified loads.
  10. JST

    Rotary Phase Converter Voltage Outputs and Step Down Transformers

    It is actually "generated", rotating magnetic field and all, so I use that. I don't object to "manufactured" however. The other two line are "pass-through" from the source. The RPC does nothing to them.
  11. JST

    Metal lathe, possibly hand-built

    The chain does appear to be a substitute for a rack. Also looks possible that the bed is a casting. There are no visible screws in it, aside from two that are visible in the view from the headstock end on the operators side. Those two are evidently through the plate and into the bed.
  12. JST

    Motor reversal

    While it was presumably missing from yours, there are often instructions on the motor. They may be on the data plate, or on the inside of the wiring box cover. Generally this consists of something like "reverse the black and red wires" or "reverse wires 5 and 8" if the wires are labeled...
  13. JST

    Fred Dibnah

    I dunno, didn't grow up with anything like that, pretty far from a Minnesota accent, but I got nearly all of it. Had to turn the sound up a bit, "bu' after tha' it were alrigh' ".
  14. JST

    B&S 2L Surface grinder oil pump help

    23-3214 looks like an orifice and maybe check valve. Could be just a tubing end fitting, I suppose.
  15. JST

    B&S 2L Surface grinder oil pump help

    The other may just be in the Bijur regulators, which IIRC have check valves if for piston pump systems.
  16. JST

    OT: Sizing a VFD for an Ice Cream Maker with Multiple Motors/compressors

    Obviously the VFD only needs to do the job. It does not have to be 3x larger than what does the job. You need to figure out what the "job" means in terms of current requirement. All you have to do is cover the requirement, plus a bit for margin. That is going to vary depending on the total...
  17. JST

    B&S 2L Surface grinder oil pump help

    "How to get it pumping"? That is a rather open-ended question, as there are any number of reasons for it not to pump. What kind of pump? Piston, I would assume, but.... If the piston is moving, but it will not pump, my first areas to check would be "is oil getting to the piston/cylinder...
  18. JST

    OT: Sizing a VFD for an Ice Cream Maker with Multiple Motors/compressors

    The VFD is running motors. That is what it is designed to do. The "other option", which I assume is a Phase Perfect, is essentially the same thing, but just set up for one output line, not three. The innards of the "PP" which output power are the same basic design as a VFD, and they are...
  19. JST

    OT: Sizing a VFD for an Ice Cream Maker with Multiple Motors/compressors

    Oddly, rectified loads with SMPS in them like the power supply or computer are pretty tolerant of even square wave power. Of course, the power wiring needs to be routed away from sensitive areas, but that is normally already done for reasons of EMI output reduction. The VFD MAY need to be...
  20. JST

    OT: Sizing a VFD for an Ice Cream Maker with Multiple Motors/compressors

    People here have run their whole shops off of a single higher rated VFD. Of course you cannot do variable speed, at least in most cases. The VFD has to be in V/Hz mode, nothing that requires the VFD to auto-tune itself to the load. And, you cannot depend on the VFD to provide current...

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