Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill
Posted by
Bob McKnight
on 2004-01-04 19:09:13 UTC
To: CAD_CAM_EDM_DRO@yahoogroups.com
From: "vavaroutsos" <pete@...>
Date sent: Mon, 05 Jan 2004 02:58:52 -0000
Subject: [CAD_CAM_EDM_DRO] Re: Converter or
Inverter for 2hp Bridgeport mill
Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com
petev
Ok, that settles that, I will leave the variable speed on the
rotary convertor as it is well along, but will spend my time
on the tried and true circuits which are described in several
articles. I have relays and capacitors to finish in a more conventional
manner and will include metering on each leg. I don't know how
good the Chinese clamp on ammeters are, but for less than $10
apiece, I can calibrate them against a known one and have a
pretty good idea of what each leg is doing. I have an Olllld Elox
Electron Drill (probably 50 year old predecessor to EMD) . I
have a clamp on ammeter in its electrode circuit so I don't blow
the circuit breaker.
Bob McKnight
[ Double-click this line for list subscription options ]
Bob, I'm no expert on generators, but I don't think many generators
are built like an induction motor. My guess is generator rotors either
have permanent magnets or coils with slip rings.
While it's true that over speeding an induction motor will generate
power, it only works because there is a field in the stator to induce
current in the rotor. I don't know how you would start a generator
like this unless there was enough residual magnetism in the rotor.
~petev
--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bob McKnight"
<bobmcknight@c...> wrote:
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From: "vavaroutsos" <pete@...>
Date sent: Mon, 05 Jan 2004 02:58:52 -0000
Subject: [CAD_CAM_EDM_DRO] Re: Converter or
Inverter for 2hp Bridgeport mill
Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com
petev
Ok, that settles that, I will leave the variable speed on the
rotary convertor as it is well along, but will spend my time
on the tried and true circuits which are described in several
articles. I have relays and capacitors to finish in a more conventional
manner and will include metering on each leg. I don't know how
good the Chinese clamp on ammeters are, but for less than $10
apiece, I can calibrate them against a known one and have a
pretty good idea of what each leg is doing. I have an Olllld Elox
Electron Drill (probably 50 year old predecessor to EMD) . I
have a clamp on ammeter in its electrode circuit so I don't blow
the circuit breaker.
Bob McKnight
[ Double-click this line for list subscription options ]
Bob, I'm no expert on generators, but I don't think many generators
are built like an induction motor. My guess is generator rotors either
have permanent magnets or coils with slip rings.
While it's true that over speeding an induction motor will generate
power, it only works because there is a field in the stator to induce
current in the rotor. I don't know how you would start a generator
like this unless there was enough residual magnetism in the rotor.
~petev
--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bob McKnight"
<bobmcknight@c...> wrote:
> To: CAD_CAM_EDM_DRO@yahoogroups.comGenerators.
> From: "vavaroutsos" <pete@v...>
> Date sent: Mon, 05 Jan 2004 00:42:44 -0000
> Subject: [CAD_CAM_EDM_DRO] Re: Converter or
> Inverter for 2hp Bridgeport mill
> Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com
>
> petev
>
> OK
> Let me explain where I am coming from and I sure never got this out
> of a text book. Generators are Motors and Motors are
>of
> I question this with some of the static motors, but it is from lack
> knowledge, not misinformation.bought
>
> I have been told and again never checked it out that if you over
> speed an induction motor it will become a generator. I kinda
> this based on residual magnetism.would
>
> So your explaination makes sense because I would be operating in the
> middle of the area between motor and generator which would no
> current flowing or no energy applied. Except I figured I
> be supplying a little energy, but I figured I was supplying energyto
> overcome mainly friction forces, but I can see that is not thecase.
>way.
> I am at the stage I was many years ago with pumps. I thought that
> shutting off the flow of water would make the pump work harder(true
> for piston pumps). But in centrifugal pumps.either air or water,
> throttling the input reduces current flow. I learned this the hard
> I took a blower unit out of a furnace and ran it just as a vent fanin
> the shop. It burned up. Fortunately I had more and shut offalmost
> all the air on the side opposite the motor to get the current downtransformer.
> where it belonged. Which brings up another question. Most
> convertors are used to run motors. I am using this to run large a
> large welding
> See any problems with the weak leg. The local power companyturning
> can supply 3 phase for a price and it will have a weak leg.
>
> Bob McKnight
>
> [ Double-click this line for list subscription options ]
>
> Bob, I assume you are using an induction motor? If so, the magnetic
> field in the rotor is caused by the slippage. If the rotor is
> at the same speed as the stator magnetic field, it does not see afield
> moving field and no currents will be induced. Without a magnetic
> in the rotor, you won't get any voltage on your generated leg. Ifyou
> don't beleive me try just spinning the motor with no windingscreates
> connected. No voltage will be generated because there is no field in
> the rotor.
>
> When an induction motor is loaded, more slippage occurs. This
> more current in the rotor and a stronger magnetic field. This inturn
> balances the force of the load on the rotor.the
>
> ~petev
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bob McKnight"
> <bobmcknight@c...> wrote:
> > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > From: "vavaroutsos" <pete@v...>
> > Date sent: Sun, 04 Jan 2004 18:33:33 -0000
> > Subject: [CAD_CAM_EDM_DRO] Re: Converter or
> > Inverter for 2hp Bridgeport mill
> > Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com
> >
> > Petev
> >
> > It started out that way. The motor I am using is a 15 HP unit.
> > After looking at the voltage differences and the phasing, I got
> > idea that some of that may be caused by the slippage fromasked
> > synchronous. So, since I was going to use a motor to start the
> > convertor, I decided to try to eliminate the slippage. I have
> > around and even my EE friends don't know. I thought somebody herestart
> > might know, if not, I will just plug along.
> >
> > Thanks
> > Bob McKnight
> > [ Double-click this line for list subscription options ]
> >
> > Bob, what are you using the small motor for? Is this just to
> thethe
> > rotary converter? Why don't you just add a start capacitor and
> > potential relay. If you're building a small unit, you could use a
> > Supco SPP-8E hard start available from www.grainger.com (4MG78).
> >
> > If you use run caps to both single phase legs and a good motor you
> > should get a nice generated leg. My generated leg varies about 10V
> > from no load to full load and the phase angle is pretty good.
> >
> > ~petev
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bob McKnight"
> > <bobmcknight@c...> wrote:
> > > To: CAD_CAM_EDM_DRO@yahoogroups.com
> > > From: "ibewgypsie" <ibewgypsie@h...>
> > > Date sent: Sun, 04 Jan 2004 06:50:28 -0000
> > > Subject: [CAD_CAM_EDM_DRO] Re: Converter or
> > > Inverter for 2hp Bridgeport mill
> > > Send reply to: CAD_CAM_EDM_DRO@yahoogroups.com
> > >
> > > Hi
> > >
> > > am new to the group, so hope this is appropriate.
> > > The Home Shop Machinist just completed a series on rebuilding
> > > Bridgeport. I am building a rotary converter and wonder ifanybody
> > > knows if turning the rotary transformer at synchronous speedwould
> > > help even out the current available from each leg. I have asmall
> > > motor with a mechanical variable speed drive that I amattaching
> tothe
> > > the old motor that is the heart of the machine. Also have
> > > capacitors to help 'tune' the system.
> > >
> > > Bob McKnight
> > > [ Double-click this line for list subscription options ]
> > >
> > > I used a toshiba single phase in, 3 phase out inverter. I used
> > > bridgeport relay to turn on with dry contacts, left theoverload
> into
> > > place (overkill since inverter monitors too). I gutted the cnc
> > drives
> > > and upgraded at that time too thou. Inverter works great.
> > >
> > > My phase convertor made the head rattle, inverter is much
> smoother.
> > > Money well spent. I have my machine on a 30 amp 220 single phase
> > > circuit now. Like I said I upgraded the cnc drives too. The 3
> phase
> > > cnc drive transformer had to go.
> > >
> > > David Cofer
> > >
> > >
> > >
> > >
> > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "john_glynn57"
> > > <john_glynn57@y...> wrote:
> > > > I have just taken delivery of my own Bridgeport mill and want
> > > > know which is the best option for powering the machine : anL100
> > inverter
> > > > or a converter. My research to date suggests that a Hitachi
> > > > inverter is the way to go however I want to question this asunit
> > > > follows: 1. I can run a dedicated 20A or 30A supply to the
> machine
> > > > which should be able to handle the startup current demand of a
> > > > converter. 2. If I use a converter I can use all the original
> > > > Bridgeport systems without mosification ie Bridgeport speed
> > > > control,forward and reverse,3phase coolant pump and shaping
> > > > which is attached to the machine.the
> > > >
> > > > My plan is to circumvent the original Bridgeport wiring and
> drive
> > > > the Main motor(s) directly from the hitachi unit and setting
> > > > motor speed at the low speed of 1400 and not using thevaliable
> > > > speed control of the machine at all. The hitachi will give methe
> > speed
> > > > control by varying the frequency however I do intend to use
> > > > original forward reverse switch. In addition I plan toreplace
> theto
> > > > coolant motor with a single phase model.
> > > >
> > > > Am I doing the right thing.
> > >
> > >
> > >
> > > Addresses:
> > > FAQ: http://www.ktmarketing.com/faq.html
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>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
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> it if you have trouble.http://www.metalworking.com/news_servers.html
>be
> http://groups.yahoo.com/group/jobshophomeshop I consider this to
> a sister site to the CCED group, as many of the same members areAddresses:
> there, for OT subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC
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>
>
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it if you have trouble. http://www.metalworking.com/news_servers.html
http://groups.yahoo.com/group/jobshophomeshop I consider this to be
a sister site to the CCED group, as many of the same members are
there, for OT subjects, that are not allowed on the CCED list.
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THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO
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Discussion Thread
john_glynn57
2004-01-02 09:41:05 UTC
Converter or Inverter for 2hp Bridgeport mill
Lee Studley
2004-01-02 11:11:25 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
Lee Studley
2004-01-02 11:21:12 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
cnczeus
2004-01-02 12:26:19 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
vavaroutsos
2004-01-02 13:36:38 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
john_glynn57
2004-01-02 15:05:22 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
cnczeus
2004-01-02 17:12:26 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
vavaroutsos
2004-01-02 18:36:23 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
ibewgypsie
2004-01-04 00:15:50 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
cncgramps
2004-01-04 07:15:17 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
Bob McKnight
2004-01-04 07:56:45 UTC
Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill
vavaroutsos
2004-01-04 10:23:10 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
vavaroutsos
2004-01-04 10:33:37 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
Bob McKnight
2004-01-04 11:00:35 UTC
Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill
john_glynn57
2004-01-04 11:03:20 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
vavaroutsos
2004-01-04 16:42:48 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
Bob McKnight
2004-01-04 17:07:03 UTC
Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill
vavaroutsos
2004-01-04 18:58:55 UTC
Re: Converter or Inverter for 2hp Bridgeport mill
washcomp
2004-01-04 19:05:21 UTC
Re: Converter or Inverter for 2hp Bridgeport mill - OT?
Bob McKnight
2004-01-04 19:09:13 UTC
Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill
Jon Elson
2004-01-04 19:27:35 UTC
Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill
ccq@x...
2004-01-05 07:48:48 UTC
Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill - OT?
Jon Elson
2004-01-05 09:19:02 UTC
Re: [CAD_CAM_EDM_DRO] Re: Converter or Inverter for 2hp Bridgeport mill - OT?