Hi folks, I have a machine (grinder) that has the below tag on it.
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Question, can I run this with a rotary phase converter. As it is now, I have a 230v outlet that runs to a rotary phase converter (5hp) and fro this, I run my Bridgeport Mill and Clausing lathe. Is this usable for this grinder as well (please see tag). I have this in my shop and have yet to run power to it (I have 200 amp service in my shop, just have not ran power from the breaker box to the grinder.
That "230/460" means that it can be wired (internal to the motor's connection box) either for 230 V three phase or 460 V three phase, pretty much the same as your Bridgeport's motor.
Where are you living? It is a 60 Hz motor, and if you are living in the UK, you will almost certainly have 50 Hz power, and the motor may overheat when run on 50 Hz.
Is your rotary coverter tuned for current and voltage balance? It apparently makes a difference in the finish produced by a surface grinder, and it is more sensitive to this than most other machine tools. It should run anyway, just perhaps not produce as nice a finish as you would prefer.
Does the grinder have any other use for the power other than the motor? If it has controls or single-phase motor running power feed, it might be worth while looking at the wiring and making sure that the single phase power is derived from the two wires which go on through to the 230 V service, so it does not see a dip when the spindle motor starts -- though it is probably not going to be a problem with that small a spindle motor.
Yes, if you are in 60 hertz territory, but you need to know whether that grinder is currently wired for 230 or for 460. Make sure it is wired for
230 volt operation. You say you have a 230 volt outlet that runs your rotary phase converter, so that implies to me that your Bridgeport and Clausing lathe are already wired 230 3 phase. When you say ---have not run power from the breaker box---, I assume you mean that you haven't run power from the phase converter to the grinder.
Gunner, cutting and running..... Political Correctness
A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
Hi Pete, Yes, this is new to my shop, shop is 2 weeks old and have not ran power from my panel to any equipment and have yet to move my mill and lathe.
You add capacitance between the output phases to produce equal current out each leg into your motor load. Ideally it is tuned for a single horsepower load, though it will probably be close enough for all if you tune it for the grinder's motor.
There are two wires (L1 and L2) which are the power company power carried through the box where your wiring for the rotary converter lives, and a third wire which comes from the idler motor only (which we'll call L3 here). Start out by adding AC rated capacitance (oil filled units) across the L1-L3 pair while watching the current measured with a clamp-on ammeter to each of the three phases. Adjust for the point where all three are the closest. After you have that one set, try more between L2-L3. You may need to reduce the capacitance between L1-L3 as you add between L2-L3. (If when you first add capacitance to the L1-L3 pair things get worse instead of better, then switch to the L2-L3 pair instead, and only add more to L1-L3 once things are pretty close. Let's see -- you've got a 5HP motor as the idler? Perhaps start by adding in increments of 10 uF or 20 uF per try.
Once you have this as balanced as you can manage, you can do a bit more tuning which will reduce the current drawn from the power line (not power you *pay* for, but it will reduce nuisance trips on the circuit breaker feeding the idler) by adding capacitance across the L1-L2 pair -- while monitoring the current in the leads between the breaker panel and the converter -- and add the capacitors on the motor side of the point where you are metering. Adjust the capacitance here by increasing the value until the current stops decreasing with each addition and starts to increase -- then back up to the last previous value and just leave it on the motor (after whatever switch you use to disconnect the rotary converter, so it is not on the line while the converter is not running.)
I hope that the above is sufficient to help you.
Probably the best articles on this topic would have been posted several years ago in this newsgroup by Fitch. Use Google to wade through the past ones, searching for "tuning" and "rotary conveter" in the same article -- Or go to the FAQ site and download all of the archived history (ending a few years ago -- but covering the time when Fitch was posting). Beware, however, that at least one year's archives includes several copies of a Windows virus. If you are not using Windows, you don't care, but if you are, you should make sure that your virus scanner checks out the files after you've uncompressed them to quarantine the nasties.
Is your converter a home-built one or a commercial one? Both can usually benefit from tuning.
A doctrine fostered by a delusional, illogical liberal minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.
When one speaks of "balanced" rotary phase converters, voltage, not current, is what is being balanced, more or less.
You can not go about adjusting capacitance in a RPC with a clamp-on ammeter. There will never be equal current in the 3 legs because you are not generating 3 distinct phases. What you are adjusting is a complex network consisting of idler motor, load motor and capacitors. RPCs are balanced by adjusting 2 sets of capacitors, each set connected between each line side and the 3rd leg. Capacitances are adjusted until the voltages across each set are equal to the line voltage or nearly so. Fitch taught us to balance RPCs with a voltmeter.
After the RPC is "balanced", incoming line current can be minimized with a clamp-on ammeter as Don suggested.
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