Can you not use the static to start a stand along motor with no load - spin that up and then the field and power in the windings will in turn drive the other motors and compensate on-the-fly.
Martin
Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
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According to Chuck Sherwood :
Since the horsepower is a function of both the torque and the speed, this makes sense.
That sounds good -- as long as the winding for the high-speed setting can handle the current at low speed operation.
Excellent suggestion.
And -- if you're doing a lot of the same part, you might even hook a rack gear on the cross-slide, and a pinion on a potentiometer, to have a result of a constant SFM as you face. This can also help eliminate chatter at certain speeds and radiuses.
Enjoy, DoN.
According to Ned Simmons :
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O.K. The switching between the VFD and the motor is what most VFD manufacturers explicitly warn against.
That depends. If you are the only one who ever uses the lathe, you can probably depend on remembering the proper operation. However, with multiple people using the same machine, with a constant potential for a new hire to not have it locked into his memory yet, I would think that such an interlock would be well advised.
Enjoy, DoN.
[ ... ]
[ ... ]
O.K. This is a reasonable approach, as long as the motor is not mechanically unusual in its mounting, thus making the finding of a replacement more difficult.
Enjoy, DoN.
Joe..save yourself some money and build a 7.5hp rotary converter. Even rope start works very well for this application. You should be able to find a good used motor for very little money (Id give you one if you were closer), or simply add a pony motor and spin it up then apply power to the big motor. Shrug..Im just about done with a 10hp pony motor run PRC that runs even my big Clausing 1501 (7.5hp) in full reverse/forwards applications, along with my big 3ph mig (though not at the same time )
You DONT need the bells and whistles of a self starter, unless you absolutly want to.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Absoutly correct Don. Bad things MAY happen when switching the lathe controls when operating via a VFD.
I pulled all my lathes off the several VFDs and run them all on a 5hp RPC for this reason.
The sole exception is that 9-18 Rivett that I wound up with several months ago. It has a two speed motor..but last weekend, for the first time I pulled the tarps and shrink wrap off of it..and discovered the damned thing is 480vts....(Im not happy camper with a certain Vietnamese charector because of this)
I could stick in one of the very very expensive 2 speed Hardnge motors I have on hand...but I can sell them for more than the lathe is worth..so will likely put in a single speed 3ph motor and run it off a VFD. Its only a second ops lathe..so its no big deal.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
I'm not sure I understand exactly how bad things might happen with a VFD. Do you mean switching something like a dual-speed motor or some other electrical control while it is being driven?
Correct. If for example..I were to use the onboard reversing switch...it momentarily interupts the power from the vfd..then spikes it badly when it makes up again. Some serious spikes.
Think of it as spiking the clutch on your vehicle..while doing "hole shots".
Sooner or later something will bust. With luck..it will simply be a universal joint..but it could be the differential or tranny.
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Gunner,
Thanks aga>
Yep. Did that. Or torquing against the brakes on an automatic. Never broke anything like that I can remember. Other ways... other stories... mostly dumber.
Gotcha. Thanks.
Uhhhmm... but an RPC is better for not causing problems when you power switch? Just thinking out loud. But I'm not worried yet.
After posting a couple weeks back about slowing my lathe, I ordered a Hitachi VFD and found a motor, cheap and local. Amazing what a handful of electronics can do these days. I had to read the book for a few days to begin to understand what to think about setting and how I might want to interface to it. Incredible configuration options in the VFD.
Need to go buy some wire this morning to hook up the motor, then I'll try it on the ground for a while. I plan to bypass most of the existing lathe electrics, so I think it will all be good and I should have new things like jog too.
I'll probably resurrect the other thread after I get things going, or if I find some uglies.
Yes..because an RPC doesnt use delicate electronics. It uses the brute force method.
Use the existing lathe Switchs to operate the VFD. Virtually everything is there already, though in some cases..if for example your forward/reverse switch was a momentary and picked a relay..you may have to replace it with a maintained version, though some VFDs have momentary input options. They are actually an amazing contraption and the designers have gone to great lengths to make them as usable as possible under just about any configuration you can imagine. Well..the good ones anyways . From machine tools to pumps, air handling and motion control. And Neptune washing machines......
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
Yeah. The thing that really amazed me reading the manual is the capability for PID feedback control in various kinds of ways. I don't plan to use that, but I never expected it to be there.
My current plan is to remove the existing control panel and replace it with one of my own design. Existing panel has three identical sized buttons for Fwd Stop and Rev. I'd like to find a big red button in case I ever need to panic-stop the thing. Had one scary screw-up already.
Also plan to remote the speed knob and add a control for jog. This VFD allows lots of remote functions through low-voltage wiring. Seems like it shouldn't be very hard to set up.
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