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  1. JST

    Motor duty 6-50 socket?

    You can often get away with that, but standard breakers are not rated for a "lot" of operations, as with "switch duty". There are breakers rated for that, but they are not as common and may not be available for your panel.
  2. JST

    Motor duty 6-50 socket?

    The item Rons linked is specified and rated to interrupt full current. That means it can be used as a disconnect in any definition. Don't know but doubt it is rated for any inrush when plugged IN. So not suitable for that. UL is indicated at top of catalog page, and in listing part of...
  3. JST

    Motor duty 6-50 socket?

    Plugs are accepted as a "disconnection means" in most cases. Not as a switch, but as a positive disconnect that will not allow power through when disconnected. When used as rated, they are not employed as switches. And when used outside their ratings, they are not approved.
  4. JST

    Converting a 480v CNC and Wire Size Question

    What you need now, is to know the exact type of service your machine needs. Or, if there is any type service it cannot deal with, that would be good info as well. Since you have "stinger" or "high leg/farm" 3 phase from the PP, there is a chance that the high leg may cause damage. If the...
  5. JST

    VFD Loud bang.

    We have not been told what voltage the machine runs on. I would think that if it was 480, that would have been mentioned, but.............. The mention that the noise seems to come from the motor is of interest and tends to support a mechanical cause, but does not prove it.
  6. JST

    VFD Loud bang.

    I like your idea of pull out the VFD and have a look. I'd have probably already done that. No telling what you may find............. I've seen many things that I would not have believed except they were right there when I looked. What you find may point out the solution. BTW, your original...
  7. JST

    VFD Loud bang.

    Yes, about 1000V/mm, although that depends on the shape of the "electrodes" the spark jumps between. A 240VAC VFD will typically have components rated for between 450 and 600V.
  8. JST

    Converting a 480v CNC and Wire Size Question

    as far as I know, ALL 208 is wye with a true neutral. Some loads may not need the neutral, but the service will always be 208 wye with neutral if it is 208 at all. There is no reason for any other type, as the point of 208 is the 120V from line to neutral. The problems come in with "220V"...
  9. JST

    VFD Blew up

    Actually, one leg of the RPC is LOWER.* You can boost it at no load with capacitors, but the effect drops with load. You can do better boosting with a transformer, but that leg will always be weaker than the "pass-through" legs (the other two). That's not really a big negative for most motor...
  10. JST

    Converting a 480v CNC and Wire Size Question

    Check the manual for acceptable supply voltage and connection types. If you have 208VAC with neutral, then yes, that is what the transformer supplied. But, most 220/230/240 3 phase is supplied by "corner grounded delta" or else "stinger" 3 phase / "farm 3 phase" / "lighting tap 3 phase". The...
  11. JST

    VFD Loud bang.

    it takes a goodly amount of voltage to jump any sort of a significant gap. The common 120V outlet will "flash over" at something like 6 thousand volts, and that is only a few mm. To cause a spark to jump, there has to be voltage. You would have to have some thousands of volts at one end of...
  12. JST

    VFD Blew up

    The motor is ONLY a generator when the drive "excites" it, meaning supplies a signal which would cause it to turn slower than it is currently turning. That is what the slowdown (decel) does. Without that, it will not generate except under very special conditions which won't be present with a...
  13. JST

    VFD Loud bang.

    Forget the spark idea for now. While not actually impossible (I have seen some very strange things), mostly any voltage that could arc over is much higher than what the VFD components can withstand. It would most likely have failed. Besides, you would more likely hear a sharp "snap" sort of...
  14. JST

    Best engineering screw ups

    Paints are pretty similar in emissivity. But heatsinks depend more on direct transfer than on radiation. All those fins are a neutral for radiation, but a big deal for direct surface to air transfer. The catch may occur with thickness. Paints usually do not conduct heat very well, although...
  15. JST

    VFD Blew up

    Not "entirely" true. The drive "should" protect itself. But with a high inertia load (a heavy wheel, blower, etc) the voltage can be driven up very fast. A poorly designed drive may fail to protect itself. A really poorly designed drive may not have an overvoltage protection built in. At...
  16. JST

    Need Help identifying a G. Boley lathe

    I'd bet the spindle runs either in bronze, or possibly in hardened steel bearings, as many watch type lathes did. The spindle will come out toward the nose, as there is probably a tapered bearing there. Could be another at the back, but maybe not. You need to get the collet lever mechanism...
  17. JST

    Simple 3 phase conversion

    I agree. I don't find the need for such fine speed control, myself. But, a VFD is often used for speed control, as well as simple 3 phase conversion. People have the VFD, so they want to "use it". If you start mucking with speed via the VFD, the pump gets the same speed change.
  18. JST

    Converting a 480v CNC and Wire Size Question

    OK, it is specifically for 480V delta, with some adjustments down, but not for 240. You cannot use it for operation on lower voltage. It has a secondary at 208V wye with neutral. So, there is some concern that your 220V 3 phase may not be configured in the way that the CNC wants. It may want...
  19. JST

    Simple 3 phase conversion

    Yes, it should. But the pump will have the same power frequency as the spindle motor. That might be an issue if the spindle is speeded up or slowed down significantly.
  20. JST

    Mystery clamp - ID please?

    That there is an "air clamp". You torque it down on the air and set it on some papers. Those papers are not going anywhere then.

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