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Mekanizm
01-10-2010, 09:36 AM
My Doall bandsaw came to me wired for 440. I have rewired the motor, changed the heaters and am getting this ready to run on a static phase converter (while I build a RPC).

I am will make sure that this transformer is not fed by the missing leg of the 3phase supply.

The first picture shows the transformer currently wired for 440 operation. The second picture shows some of the wires disconnected (and laying haphazardly) so that the schematic can be seen clearly.

http://i255.photobucket.com/albums/hh152/topafranklin/TransformerWired.jpg

http://i255.photobucket.com/albums/hh152/topafranklin/xformerpartiallywired.jpg

(If you look closely, I have discoverd that the three ring terminals on the black wires were all loose. Corrosion maybe? They will be replaced).

My specific question is "what do I do with black lead "1L2"?

From what I see, the black lead marked "1L1" is from a leg of the incoming power. The black lead marked "1L2" is the second leg of incoming power. The black leg marked "240V" goes directly to the grinder motor on the blade welder panel. the red wires imediately route through the shown fuse (currently 1-8/10A) and then to the coils in the relays and to the control switches. The white wires are ground wires.

So to get this guy operational, What do I do with lead "1L2" that goes to the tap marked "480V"?

Black_Moons
01-10-2010, 10:34 AM
I would say connect the 1L2 to the 120V side if its 120v or 240v if its 240v your wiring this thing to. (the 120v terminal along the bottom left that is)

It also should be noted that the transformer may have less total power capability when wired as 120v to the primary, but likey designed to take the same amount of power reguardless of primary used...
if wiring it up to run off 3 phases of 120v to neutral, you could run connect whatever runs off its output to 120v directly insted of using the transformer, but the transformer would still be needed for the 240v blade grinder (Unless you connect that up to 2 of the 3 phases for 208v, well, 240 with a static phase converter)

So basicly you could wire the whole transformer out, since its neutral is also bonded to ground, its not exactly isolating anything either.

I wonder what the L3 terminal is. Definately don't touch that while in operation! 380/480/575v terminals will likey kill you very easily.

JoeFin
01-10-2010, 10:53 AM
You could always place a 10K ohm resistor across L1 and 240 and then measure the resistance across X1 and Gnd. The resistance will be increased propertionately by the transformer winding ratio. In this case your looking for 2:1

I think you need to wire L1 to L1 then 240 AND L2 to 240 since the transformer is only operating off 2 legs of the incoming 3 phase power.

rkepler
01-10-2010, 11:28 AM
So to get this guy operational, What do I do with lead "1L2" that goes to the tap marked "480V"?

I think that you might have a problem with using that transformer - the only taps available for L2 are labeled 380, 480 and 575. You definitely don't want to connect L2 to the secondary labeled 240 - that would be OK if it were a primary, but it doesn't appear to be. Connecting L2 to there would basically short it and things would be exciting.

If the transformer didn't also have a 120V tap on the secondary I'd suggest pulling it out of the circuit and running the inputs through the fuse. I would expect that the fuse is on the secondary (for the fixed amp rating) but you can't tell the relationship with the 120V.

If I had the time I'd call DoAll and get the circuit diagram for this and for the same saw but wired for 240V. If I was in a hurry I'd disconnect the transformer, tie the incoming through a fuse to the existing secondaries and put in a 120V 150VA transformer.

J Tiers
01-10-2010, 11:52 AM
I tend to think JoeFin is right.......

But first I would measure from L1 to each of the other taps...... We do not *know* what is a secondary, but the wires at the fuse are wired up as if they are, and one is marked "X1" which would be correct.

I think that the motor wire is using the transformer as an "autotransformer" to run the small grinder motor. it is most likely part of the primary wiring.

You can easily see by measuring from 1L1 to each other tap. if they are all primaries, which I think they are, you will get increasing voltages in proportion to the numbers marked. if not, the voltages won't make sense

rkepler
01-10-2010, 12:03 PM
I think that the motor wire is using the transformer as an "autotransformer" to run the small grinder motor. it is most likely part of the primary wiring.

I can't image that they could tie any part of an autotransformer to ground. It would seem to me that the 120V output is an isolated output off secondaries.

Could the OP check the motor and see if it's a single phase or 3 phase motor? This really seems to be setup for running a single phase motor (a single lead on the 240V tap). If it's 3 phase then we're only seeing a only a part of the wiring.

J Tiers
01-10-2010, 02:05 PM
I can't image that they could tie any part of an autotransformer to ground. It would seem to me that the 120V output is an isolated output off secondaries.

Could the OP check the motor and see if it's a single phase or 3 phase motor? This really seems to be setup for running a single phase motor (a single lead on the 240V tap). If it's 3 phase then we're only seeing a only a part of the wiring.

The little motor is run off the 240 TAP on the primary, as I (and Jim) see it........

the secondary for the controls is another issue entirely. But the transformer DOES seem to be single phase, from all that is visible...... A 3phase transformer looks different, and has taps for each coil.

rkepler
01-10-2010, 02:31 PM
The little motor is run off the 240 TAP on the primary, as I (and Jim) see it........

the secondary for the controls is another issue entirely. But the transformer DOES seem to be single phase, from all that is visible...... A 3phase transformer looks different, and has taps for each coil.

OK, I see the reasoning. The main motor is completely separate from this transformer, and your thought is that all the studs along the bottom are autotransformer taps for the blade grinder? That'd be easy enough to check - disconnect things and check the resistance. If the resistance changes from the 0V to the 575 reasonably linearly then it is setup to be an autotransformer (also check that the L3 stud isn't in circuit). Similarly, if neither stud of the 120V side has a low resistance with the other studs (and low resistance between them) it's setup as a secondary with the autotransformer as a primary. If all of those are the case it *might* be possible to connect the incoming L2 to the 240V tap - if I were doing that I'd then check the 120V output to make sure that it was in range.

The confusing thing is that a 10A fuse on a 240V line is enough for a 3HP motor, it's a lot for a little fractional HP grinder motor, even considering starting surge. But DoAll did overdo things sometimes.

Mekanizm
01-10-2010, 03:03 PM
Sorry I didn't take and post this pic right off the bat. It says "Pri. Volts - 0, 120, 240, 380, 480, 575". Also "Sec. Volts - 120"

http://i255.photobucket.com/albums/hh152/topafranklin/TransformerDataPlate.jpg

Here is the terminal block feeding the grinder motor on the blade welding panel. The two black wires on the top left are the only conductors going to the kinda hidden grinder motor. The top right black wire on the right is one of the three incoming power (1L1) conductors. The second from the top on the right is the black wire at the transformer tap labeled "240V".

http://i255.photobucket.com/albums/hh152/topafranklin/TerminalBlock.jpg


A shot of the cabinet.

http://i255.photobucket.com/albums/hh152/topafranklin/Cab.jpg

Exiting the bottom of the cabinet from left to right is the two conductors for the grinder motor, the three wires for the main motor and a blue and white pair of unhooked wires going to a non-factory looking 120v duplex receptacle.

Mekanizm
01-10-2010, 03:12 PM
The confusing thing is that a 10A fuse on a 240V line is enough for a 3HP motor,

I had to look at that 2 or 3 times. I now take it to say one and six/tenths and it protects the 2 red wires (relay coils/motor controls).

doctor demo
01-10-2010, 03:37 PM
In looking at the second picture , I see a post for L3 and as been said (and shown) the transformer is single phase. So My question is : where does the other side of that L3 post go? If I'm correct it is just a dead end termination for some other ap. I do agree with the 1-6/10 amp fuse rating lable.

Steve

rkepler
01-10-2010, 03:51 PM
Sorry I didn't take and post this pic right off the bat. It says "Pri. Volts - 0, 120, 240, 380, 480, 575". Also "Sec. Volts - 120"

OK, that helps a lot - it's a simple control transformer, and all the lower studs on the panel are primary inputs.


Here is the terminal block feeding the grinder motor on the blade welding panel. The two black wires on the top left are the only conductors going to the kinda hidden grinder motor. The top right black wire on the right is one of the three incoming power (1L1) conductors. The second from the top on the right is the black wire at the transformer tap labeled "240V".

Where does the other end of the "240" line go?

Blueskys
01-10-2010, 03:55 PM
I don't think that transformer is going to work.
You can run your grinder by connecting your 240 wire
to one of your phases. But to get 110 you are
going to need a 240/120 transformer. Or run a cord
over from a 120 receptacle and use that direct.

Then just forget the transformer totally.

Mekanizm
01-10-2010, 04:12 PM
Where does the other end of the "240" line go?

To the transformer tap marked "240v".

Doctor, you are right that "L3" goes nowhere. It is unused with no wires whatsoever.

Mekanizm
01-10-2010, 04:36 PM
... Where does the other end of the "240" line go?

I need to backpedal a little bit here.

Regarding the terminal strip - The "240V" wire goes out the left side to the Blade Welding Panel (part of this panel is the grinder motor). Out the right side it runs up to the tap on the transformer labeled "240V".

Blueskys
01-10-2010, 04:51 PM
I need to backpedal a little bit here.

Regarding the terminal strip - The "240V" wire goes out the left side to the Blade Welding Panel (part of this panel is the grinder motor). Out the right side it runs up to the tap on the transformer labeled "240V".

You are going to have 208v 3phase right?
Then I would get my power for the weld panel
by running a wire from one of the incoming phases
to the right side of 240v on the terminal strip.
The 110v I would get from a receptacle. What
all is 110v? Buttons, lights, coolant?

Black_Moons
01-10-2010, 05:01 PM
I had to look at that 2 or 3 times. I now take it to say one and six/tenths and it protects the 2 red wires (relay coils/motor controls).
I think 1-6/10 meaning 1.6A makes much more sense then 'one 6 or 10A fuse'
Damn imperial bandsaw designers! Use the metric system! lol.

J Tiers
01-10-2010, 05:38 PM
As I see it, the transformer is doing double-duty, both adapting the (presumably small) motor via the primary as an autoformer, AND supplying 120V control power by the secondary (the X1 etc at top of tagboard). As long as the total VA adds up OK, it works great.

So if you don't over-think it, but just use the appropriate primary tap, it should work fine.

You'll probably need to change those 3phase fuses for the lower voltage/higher current of the main motor.

Mekanizm
01-10-2010, 06:08 PM
You are going to have 208v 3phase right?


Well.... Let me put it this way... the supply is as follows.

http://i255.photobucket.com/albums/hh152/topafranklin/SPC.jpg

The 110V conductors are the red wires of which there are two. One terminates at the terminal strip and goes nowhere. The other one goes to a relay for the motor and from there to the "On" and the "Off" button.

I am starting to see how I can use some externally provided 110v to get this done but that is not my first choice. Heres why;

http://i255.photobucket.com/albums/hh152/topafranklin/RollingBase.jpg

and;

http://i255.photobucket.com/albums/hh152/topafranklin/SupplyReel.jpg

(I would have never bought this reel outright but it was essentially given to me and perfectly suits my goal of having virtually everything in my shop on wheels. It is a 5 conductor, 20 amp cable)

Mekanizm
01-10-2010, 06:24 PM
As I see it, the transformer is doing double-duty, both adapting the (presumably small) motor via the primary as an autoformer, AND supplying 120V control power by the secondary (the X1 etc at top of tagboard). As long as the total VA adds up OK, it works great.

So if you don't over-think it, but just use the appropriate primary tap, it should work fine.

You'll probably need to change those 3phase fuses for the lower voltage/higher current of the main motor.

I don't understand "auto transformer" enough yet to fully follow the logic but it certainly seems that they are coming off of the "240V" primary tap to feed the welding panel (grinder motor) - and coming off the 120 secondary for the On/Off switches...double duty as you say.

Are what you suggesting is to simply take the black supply conductor labeled "1L2" loose from the primary tap labeled "480V" and relocate it to the primary tap labeled "240V"?

I checked the three phase fuses and they are time delay 15A. At 240V, the FLA of the motor is 9.6. OK?

Blueskys
01-10-2010, 06:35 PM
I see three options:

1. Try connecting one of your incoming phases to 240v terminal on
the transformer while leaving the lead going to the weld unit connected
also. If you get 110v at the top terminals you are all set. If the wire
going to the 480v terminal is hooked up on the other end to a phase
you can just move it over to 240v terminal.

Otherwise you have to get 110 from somewhere else
2. External source
3. 240/120 Transformer

Oops sorry. I see from your last post that this is likely
what you are going to try already.

Mekanizm
01-10-2010, 07:08 PM
.... That'd be easy enough to check - disconnect things and check the resistance. If the resistance changes from the 0V to the 575 reasonably linearly then it is setup to be an autotransformer (also check that the L3 stud isn't in circuit). Similarly, if neither stud of the 120V side has a low resistance with the other studs (and low resistance between them) it's setup as a secondary with the autotransformer as a primary. If all of those are the case it *might* be possible to connect the incoming L2 to the 240V tap - if I were doing that I'd then check the 120V output to make sure that it was in range.

I disconnected everything and found the following R values between the respective taps on the 'Primary' side;

0 - 120: 0.7 Ohms
0 - 240: 1.4 Ohms
0 - 380: 2.6 Ohms
0 - 480: 3.4 Ohms
0 - 575: 4.3 Ohms

On the 'Secondary';

120 - ground: 2.6 Ohms

There is no continuity between any taps from one side to the other.

I haven't got the confidence to put power to this yet and take voltage readings because I need to understand the Static Phase Converter and how it supplies power a little better.

Mekanizm
01-10-2010, 07:15 PM
I see three options:

1. Try connecting one of your incoming phases to 240v terminal on
the transformer while leaving the lead going to the weld unit connected
also. If you get 110v at the top terminals you are all set. If the wire
going to the 480v terminal is hooked up on the other end to a phase
you can just move it over to 240v terminal.

Otherwise you have to get 110 from somewhere else
2. External source
3. 240/120 Transformer

Oops sorry. I see from your last post that this is likely
what you are going to try already.

Regarding option 1, there seems to be a consensus building....

J Tiers
01-10-2010, 07:33 PM
.......................because I need to understand the Static Phase Converter and how it supplies power a little better.

Static converters only supply single phase...... They briefly power the third phase for starting.

Therefore, you MUST apply the "straight through" power to the phases the transformer is on, or the controls will have no power. This is always a good idea even with an RPC, of course.....

Mekanizm
01-10-2010, 09:00 PM
Static converters only supply single phase...... They briefly power the third phase for starting.

Therefore, you MUST apply the "straight through" power to the phases the transformer is on, or the controls will have no power. This is always a good idea even with an RPC, of course.....

What I had not done until just now was read the voltages of the three legs immediately after the Static Phase Converter. They all read 120 volts leg to ground. For some reason I didn't quite expect that. Maybe I was thinking that third leg stayed dead except when the starting caps were discharging on startup. Anyway, this is suggesting that my next step is to plug in the bandsaw and read voltages at the transformer.

Paul Alciatore
01-10-2010, 10:31 PM
As for your phase converter Voltages, I suspect it is really 208 V, 3 phase and not 220 V as labeled. 208 V, 3 phase should read 120 V to ground/neutral on all three phases and 208 V between any two of the phases. This is normal.

I am not sure you have given or even have all the information needed. You say you have rewired the motor. Is this the primary saw motor? It was apparently 480 V, 3 phase to begin with. What do you mean by "rewired" it? Has it been rewound for a different Voltage? Or have you selected different taps or connections with the original wires to allow it to run on a different Voltage? And is this new motor Voltage 220 V to match the phase converter? And are you aware that the motor will draw twice as much current when operated on 220 V? So did you increase the size of the three phase fuses to accomodate the higher current needed for lower Voltage operation? But before doing that, did you check the wiring and other components in that motor's circuit (contactor, TBs, etc.) to see if they can take the increased current for 220 V operation? It may be that this saw is not suitable for 220 V operation.

So if you answers the above questions allows you to proceed, then your only remaining problem is the transformer which is providing 220 V for the grinder motor and 115 V for other things, perhaps the control circuit. On this transformer, you must match the primary coil's connection to the actual Voltage you will be using (220V, I assume). The secondary on this transformer is 120 V and the primary is apparently being used as an auto transformer to provide the 220 V needed for the grinder motor. So both of these connections should remain the same. Also L1 and L3 would remain the same. The only question is the correct connection for the L2 wire. And if you are connecting to 220 V or 208 as I suspect you really have, then the only choice is the terminal labeled 220 V. The same terminal that the grinder wire (marked 220 V) is on.

What troubles me is the three lines above the Voltage labels on your panel - one solid and two dotted. They seem to indicate that the L2 connection to the primary, saw motor is connected to one of the three terminals marked 308, 480, and 570. This appears to indicate an internal jumper that can be changed if the motor's Voltage is not 480. Have you observed this jumper? My guess, and I did say guess, is that it is on the 480 V terminal and would need to be moved to the 220 V terminal where the L2 wire is connected for 220 V operation. This is my best guess. I say again that this is a guess.

But the fact that there is not a dotted line from the L2 dot above the Voltage numbers and the 220 V terminal MAY indicate that 220 Volt operation is not anticipated or recommended. Again, as I said above, this saw may not be suitable for 220 V operation. The wiring may not take the increased current. The contactor may not. Any other component in the saw moror's circuit may not. It is also possible that there is some interconnection between the 480 V motor circuit and the (120 V?) control circuit. Such a connection may not work with 220 V. The only way to be sure would be to have a schematic or to completely trace the wiring.

If at all possible, I would try to get an installation manual for this machine and read and understand all of it BEFORE you power it up. Or perhaps some factory help.

Don Young
01-10-2010, 11:50 PM
If you note that the transformer label indicates primary voltages of 120,240,...etc., you can verify that all you need to do is connect the L2 lead to the 240V tap with the grinder lead. Leave all other leads as-is. This is a straight=forward arrangement to supply an isolated 120V for the controls and an un-isolated 240V for the grinder motor regardless of what voltage the main motor is operated on.

Your converter supplies 240V between two of the outputs, directly from the single phase input with each line 120V to neutral/ground. During starting, and perhaps during running, the converter supplies a voltage somewhat less than 240V between the third output leg and either of the other two. What that leg measures means nothing as long as the motor starts and runs okay. Do not assume that the third leg is dead except when starting. Its voltage, current, and phase relationships are highly variable and it may contribute little or no power to the motor, depending on the converter design, but it is still deadly.

whitis
01-11-2010, 12:12 AM
If I read correctly, looks like you have a transformer with a beefy primary that doubles as an autotransformer for the single phase 220V grinder motor and a 110V secondary that runs something (control relays?).

Move the incoming power lead to the 220V tap. That is it, you are done (excluding the changes to the three phase main motor). In this particular configuration, you aren't even using the primary as an autotransformer and so the transformer is not even involved in running the 220V grinder motor. The transformer is just acting as a plain old 220V to 110V transformer.

J Tiers
01-11-2010, 12:15 AM
What I had not done until just now was read the voltages of the three legs immediately after the Static Phase Converter. They all read 120 volts leg to ground. For some reason I didn't quite expect that. Maybe I was thinking that third leg stayed dead except when the starting caps were discharging on startup. Anyway, this is suggesting that my next step is to plug in the bandsaw and read voltages at the transformer.

There are a number of reasons for it to show 120V on the third wire...... that is NOT necessarily due to some sort of power supplied to it, although a few designs do have a capacitor to provide some phase shifted power for running. The cap size is very motor-dependent.

When running, you will find a third phase of likely around 165V+ on the third wire, which comes from the motor. The motor will act like an RPC when it is running, but the voltage there cannot supply any power to the motor unless there is a 'run capacitor" in the converter.

Your transformer must be powered from the input leads, which will be 120V-0-120V from hot to neutral to hot.

Edit: The HIGH voltage of 165V+ vs 120V is because the actual electrical "neutral" is in the center of one of the "delta" phases, because the source voltage is 120-0-120, with the neutral at the "0" point.

There is a "virtual neutral" which is the point "in the middle of" the three motor phases, corresponding to the star point of a star motor. That point is NOT grounded, and the voltage on teh 3rd wire will be the motor "star" voltage PLUS the voltage to ground from the "virtual neutral".

Blueskys
01-11-2010, 05:26 AM
A young fellow could get a good start towards a quality education
from many of the threas on this website.

Mekanizm
01-11-2010, 10:07 AM
As for your phase converter Voltages, I suspect it is really 208 V, 3 phase and not 220 V as labeled. 208 V, 3 phase should read 120 V to ground/neutral on all three phases and 208 V between any two of the phases. This is normal.

Coming out of my static phase converter are three leads that consists of what I call two real and one fake legs. All three of these legs read 121 volts when taken individually to ground. The only reading I get phase to phase is 244v from the real leg to real leg. I get essentially zero volts when reading real leg to fake leg.


Or have you selected different taps or connections with the original wires to allow it to run on a different Voltage?.

This is correct. The nine leads coming out of the main motor were rearranged to now be at 220v operation.


And are you aware that the motor will draw twice as much current when operated on 220 V?

Yes.


So did you increase the size of the three phase fuses to accomodate the higher current needed for lower Voltage operation

The three phase fuses have been and still remain at 15A time delay. At 9.6 FLA at 220v I cannot say for sure that these are the correct fuses.


But before doing that, did you check the wiring and other components in that motor's circuit (contactor, TBs, etc.) to see if they can take the increased current for 220 V operation?

Not definitively.


What troubles me is the three lines above the Voltage labels on your panel - one solid and two dotted. They seem to indicate that the L2 connection to the primary, saw motor is connected to one of the three terminals marked 308, 480, and 570. This appears to indicate an internal jumper that can be changed if the motor's Voltage is not 480. Have you observed this jumper?

I have not seen a 'jumper' but I will look very closely again just to make sure.

I appreciate your help. I should make a phone call and see about getting the schematic for this. I like to have this in my files at any rate.

Mekanizm
01-11-2010, 10:22 AM
A young fellow could get a good start towards a quality education
from many of the threas on this website.

That is happening as we speak. I originally though that this would be relatively straightforward and I would be up and cutting material pretty soon. What these posters and you have caused me to do is go ahead and get a better understanding of what this electrical equipment is actually doing.

I have accumulated some of the basics for a RPC. This plan here is to research and educate myself to the point that any future postings could be competently discussed (by me) with hand holding kept to a minimum. In this case I underestimated what I was actually trying to do and am in the background trying to get caught up on what I probably should have known before posting. Either way the education is coming hard and fast and I am greatly appreciative to you and the others.

Your gentle comment is true.

Mekanizm
01-11-2010, 02:21 PM
Thanks to all, it is now up and running.

The solution, as many of you correctly surmised, was to relocate the "1L2" phase from the tap labeled "480V" and move it over to the tap labeled "240V".

The help I received here prepared me to make a phone call to Doall and their tech guy walked me through it (and it sounded quite familiar by now I might add). I was in no shape to do that before this thread and certainly more educated after so thanks again everybody!

Next up will be the RPC!