[Al_The_Man]

I see now that transformer is only 350va total, the windings are too low a current capacity for servo usage.
! amp or so per winding!
Al.

[billsnogo]

then it looks like I should use the other transformer (the one originally powering the servos according to the schematic) here
http://i64.photobucket.com/albums/h1...psdbc6b3b1.jpg

[Al_The_Man]

The original servo transformer should work, although it doesn't show the VA assume it would be OK.
Your DC will a tad over 200vdc however.
Al.

[DeanW]

Price is right if it could save me a lot of headaches, but would I still not need to do a soft start circuit with this before the transformer, which will also supply me with my 120v needed for other accessories?

I am not sure, you could ask Antek what they recommend.
I do not know what you mean about 120v for other accessories. I would think 120 ac is brought in on an aux contact on your main contactor. or, from an isolation transfomer. Are you saying that you have no 120v ac available swithed in any way by the main disconnect?
I do not relate 120v AC with ny soft start circuit?

Thanks to the advice of another member, I was going to use a large resistor and then a contactor that was used in the cabinet originally, and use a 555 timer to activate the contactor to bypass the resistor. Only question is, I assume (I know I should not assume, that is why I am asking) it should be used before the transformer, not after, correct?

When you say "large" resistor, you must mean a high wattage low ohm resistor used for inrush limit - where you leave it in the circuit for a second or so and them switch it out.
If you are uncomfortable with building a 555 timer circuit, instead, you could use a timed relay to switch the contactor. I do not think they are very expensive. Lots of them from China on eBay. Most of them require a base connector to plug the relay in to - so buy one that come with the base if you decide to go that route.

This is new to me, so I need to ask a dumb question, is this resistor going across the capacitor buss? Speaking of which, do most people make there own for a capacitor bank?

OK, for the supply, the buss is simply wire (use 10 AWG) connecting the caps in parallel. The resistor is called the "bleed" resistor and the circuit I posted allows it to be a small value to bleed the charge quickly so you do not have a larger value across the caps drawing current all of the time. Either way, you need a bleed resistor(s).

I see the attachment for the transformer. It would be good to know what KVA it is.
If I am reading the diagram right, the primary is on top and the secondary is on the bottom. You should be able to connect the 240 L1 to the 0v and L2 to the 380v terminal. This should output about 92-95 volts AC on the 150 output right of 0. Rectify and you should get about 128-134 VDC.
If someone sees that is wrong, please speak up.

There really is no way to know if the transformer will provide enough amps without knowing its KVA rating.

Dean

[Al_The_Man]

The first (undersized) transformer had a 120v control winding, which had the transformer been large enough capacity would have saved bringing in a neutral for 120v control.
The second TXFR was used for the original servo's so we could assume this should be high enough VA.
I just realized the second transformer is an auto transformer so there is no isolation between windings.
So as Dean pointed out, you could use the 20v to 220 for the 240v supply and use the 220 and 380 volt winding for the DC supply this will however give you 225vdc. (160 x 1.414).
You will however have to be careful that the servo supply is not connected to chassis or earth ground.
Al.

[Al_The_Man]

If the drives have isolation between power and the control inputs, then you can use a non-isolated supply, Another option with the auto transformer to get lower drive supply voltage is come off of the 380 and 460 = 80vac = 110vdc.
The Dugong drives show that they have isolation on the command inputs so it should be possible to use a non-isolated supply.
Al.

[DeanW]

I thought this big transformer was going to be dedicated to the high amp DC supply? If not, then I do not see how it is useful at 200+ rectified when < 150 is needed.
If dedicated, applying 240 to the 0 and 380 inputs (top side of drawing), should yield < 95VAC at the bottom 0V to bottom right 150V output. Rectifying that would get < 134V DC which is in the DC range needed.

Am I missing something... Am I mistaken?



Dean

[Al_The_Man]

It is an auto transformer so conceivably any pair of windings could be used for the DC supply, such as I mentioned, 240v supply in on the 20 & 220, and out from 380 & 460 (80vac = 110vdc).
The down side here is it puts the DC at a considerable potential above ground.
It may be wiser at this stage to look for a more suitable TXMR. That is if the original 150vac windings with the resulting 210vdc is going to be too high?
Al.

[billsnogo]

The first (undersized) transformer had a 120v control winding, which had the transformer been large enough capacity would have saved bringing in a neutral for 120v control.
The second TXFR was used for the original servo's so we could assume this should be high enough VA.
I just realized the second transformer is an auto transformer so there is no isolation between windings.
So as Dean pointed out, you could use the 20v to 220 for the 240v supply and use the 220 and 380 volt winding for the DC supply this will however give you 225vdc. (160 x 1.414).
You will however have to be careful that the servo supply is not connected to chassis or earth ground.
Al.

I could use the first transformer I posted for my 120v control, just like the original schematic shows, and then use the second for my servo power supply.

Why no ground for auto transformer?

[Al_The_Man]

The first could be used for the 120v control, the down side is it is only 150va winding or around 1.5amp!
For the second TXFR you could use the 150v unless this is going to be too high for your drives, >200vdc?
If you use the 380-460 terminals for 80AC, this produces a DC supply that is ~400v above ground, which could put stress on components, apart from the safety issue.
An auto transformer has no isolation from the supply, so all output terminations are referenced to ground due to each of the 120v supply legs being referenced through the grounded neutral, in spite of no neutral actually being connected to the transformer.
So if any AC or DC power terminal becomes connected to ground, it provides a short circuit.
Al.

[billsnogo]

The second TXFR was used for the original servo's so we could assume this should be high enough VA.
I just realized the second transformer is an auto transformer so there is no isolation between windings.
So as Dean pointed out, you could use the 20v to 220 for the 240v supply and use the 220 and 380 volt winding for the DC supply this will however give you 225vdc. (160 x 1.414).
You will however have to be careful that the servo supply is not connected to chassis or earth ground.
Al.

I found the label for this transformer sitting at the bottom of the cabinet. It is a Bosch type 911 112 K+G No. 231 The rest of the label is harder to read but can make out
UVW 210-460 V, (unreadable)A P1 1KVA (assume that is single phase 1,000va?)
u1,v1,w1 2x150 V 6,66 A 100% ED


So.....if I do as dean suggest and hook up my 240 to the 0 380v primary, I would get 94.73VAC difference on the secondary on the 0 and 150 outputs, rectify it (x1.41) 133.58VDC.

so, I am guessing this is a 1,000va Transformer? So if I draw 94.73V from the secondary of a 1,000 transformer, that gives me 10.55 amps? (divide the 1,000va by the 94.73 voltage pulled from the secondary resulting in 10.55A? Or 1000va by 80v resulting in 12.5A) That is not any more than the antek power supply..... Maybe no more is really needed for decent performance?

Only concern (since I am still reading and trying to learn) what this potential above ground is/does? I really don't want to have any unsafe conditions.

The transformer (and inductor that is connected to it) had a chassis ground, this would not cause a problem since it is not directly connected to an input/output, would it? That is only for safety sake if there was a short circuit?

So far I am thinking about buying the inrush unit, a power supply if one large enough can be found for a somewhat reasonable cost, otherwise TRY and use the transformer as dean suggest, or like Al says using the 380 and 460(but worried about this potential above ground thing, I know I am slow on the uptake, but I am trying), add in a couple of the large canister screw terminal capacitors I had been asking about (like these Two 12 000uF 450V Cornell Dublier Capacitors 12000 Uf | eBay ) and call it good?

Would it be wise to use the inductor after the power supply setup, or not really necessary?
http://i64.photobucket.com/albums/h1...wanka/004s.jpg

THANKS AGAIN TO ALL!

[Al_The_Man]

One thing with using the lower voltage on the higher voltage tap is that the TXMR is derated somewhat, i.e. less efficient.
Whether this will make alot of difference would have to be seen.
The ground reference means that being an auto transformers and fed from a grounded supply (120-N(G)-120), any subsequent secondary circuit or DC obtained from it cannot be connected to ground. which the original obviously was used this way.
You should only need one of the 12,000µf
The inductor won't really be necessary.
Al.

[DeanW]

It looks like the transformer is only rated high enough to run one motor at a time. The label you quoted says "6,66 A" - that is the rating you have to go by (150v @ 1KVA is 6.66 Amps). At any voltage, it is rated at 6.66 amps continuous. It is not rated at 10.55A at 94.73VAC, or 12.5A at 80VAC... it is always rated 6.66A.
So, the previous discussion about the transformer may be irrelevant. It looks like you will want a higher rated transformer to build your supply, or you could use an Antek 1500W supply. For instance, their 70v supply has two outputs that can be run in series for 140v at 11A continuous. However, their supplies are conservatively rated and they state that you can draw 20% more = 13A continuous and 200% (22A) for a minute or two. If you go with a lower voltage, you can get more amps. But, your top speed will be reduced.
From past discussions, others have stated that 2/3 the total motor ratings should be enough... that would be 2/3 of 20 (6.66*3) which is about 13A. How convienient!
If the others are correct, then an Antek 1500W 70v supply with the two 70v outputs wired in series for 140v will work for you.
It seems like building a supply from scratch would not cost much less - unless you get great deals.
Hopefully, someone else knows if 13A with 20A or so for a minute or two is enough to run your motors. I am not sure. But, now that you have posted some specs, I do not think that the transformer you have is going to cut it.
How far does one turn of a motor move an axis? What is the max IPM that you want? You can use a lower voltage than the motors rating, you will just get a lower top speed. But, at a lower voltage, you will get more amps from a 1500W supply.

BTW, I am not affiliated with Antek in any way.

Dean

[Al_The_Man]

The original full print shows all three original motors ran off of this one transformer, the subject of the VA and current is limited by the wire gauge, for example if you were to take 20% turns off, the current capability would rise the same % as long as the wire gauge supported the extra current.
I usually use Antek or on ebay known as Jonango for new applications, usually just the transformer and build my own.
Al.

[DeanW]

The motor driver was powered from the transformer. But, I believe the controller only powered one motor at a time (not cpapable of running 2 or 3 at a time).
That is from what Bill posted elsewhere about the control.
Dean

[Al_The_Man]

This is what I have on the TXMR T2.
Al.

[DeanW]

That schematic has 3 drives each with its own command input. The one Bill posted shows only one command input and 150v (vs. 180) outputs on the transformer. I do not know... the 1KVA 6.66A seems weak to me.
Are you saying the 1KVA 6.66A transformer he has can provide enough power at 120V+ for his motors under CNC control?
I was thinking he needs more power (Tool man grunt)
Dean

[Al_The_Man]

I would tend to go with core size to get an idea what the capacity of the transformer.
I have retrofitted XLO's, about the same size as a B.P. with SEM motors, these had 26lb-" 140v 8.8amp motors, I used the original transformer which I would estimate to be between 1Kva and 1.5Kva.
If Bill is using the same transformer and motors and the transformer fed all three drives, then presumably it should do the same with different drives, but the voltage issue is still there?
Al.

[billsnogo]

A huge reason for this retrofit is so I can drive all three motors at the same time to do true 3D milling, as it was designed to drive only one axis at a time and really is not of much use to me. The diagram there is the the MDI 151tnc, which was a step up from mine as it had three different drivers compared to my one so it could do at least 2.5D milling. Maybe that is why they put a smaller transformer in this as a bigger one was not needed. I guess I need to either buy a larger one, or try and find a large power supply already fabbed up.

More questions to come when/if I find possible alternatives.

thanks again guys

[Al_The_Man]

I guess I need to either buy a larger one, or try and find a large power supply already fabbed up.

Maybe the best thing at this point.
Al.