Alln1DC Bridgeport series 2 interact 2

[Snap-On Phil]

About the Autotransformer ? I’m using 220v single phase . I’m not an electrician, but I have a 110 leg on 20 on one side of coil and other 110 leg on the 460 on other coil. When I put volt meter Leeds on 180 on one coil and 0 on other coil it reads 89.1vAC by the 1.41 multiplier for rectifier that gets me 125.vDC and my Servo motors are 140v

Can this transformer be wired this way or is this not going to work.

[cncsnw]

I think you need to get someone who is familiar with electricity and transformers to look at it.

That person could disconnect all wires, then check continuity between the different taps. That would determine whether it is an autotransformer, or whether it has isolated primary and secondary windings.

It almost looks like maybe the 0/180/210/.../460 taps go to primary windings, and the 0/20/180 taps go to secondary windings.

But if that were the case, then applying one leg of 110VAC (or 120VAC, if you live in North America) to the "20" tap on one side, and the other leg to the "460" tap on the other side, would not yield any output; so that is confusing.

It is likely you can use this transformer, and it will work just fine. But you need to get someone who knows what they are doing to get their hands on it and tell you how to connect it.

I am assuming, through all this, that you do not have any original wiring diagrams that would simply show you how the transformer windings are related, and how they were used in the original control.

[Snap-On Phil]

So my servos say 5.0NM around 40 something inch pounds with voltage of 140vdc. So do have to use a CAPBDHI ? I’ve watched cnckeith’s videos explaining the use of the cap boards he shows the power tron motor with voltage of 140v but motor is 30 inch pounds in video with use of transformer.

Looking over the schematics of the 2 cap boards ( hi and low ) the drawing doesn’ show a rectifier and uses a varister on the dc side of hi board and uses a different voltage cap. Where the drawing for the low show a rectifier. Just asking where does the dc come from with the cap high board ?

Either way I don’t care which board I use just asking for the correct one so I can get on to next item.
The mill originally worked with a rectifier off of the transformer that i currently have.

I’m looking for just the cap board. as I have a 12000 uf 450v capacitor, unless it needs to be one of 2 shown on schematics ( low ) using a 250v and (high ) using a 16ov

[centroid467]

How many wires are going to the currently installed rectifier? Can you post photos of it?
If you know it is putting out 125 volts and working, why change it at this point?



CAPBRDHI does have a rectifier on it - two diodes for rectifying from a center tapped secondary as Marc explained.


No, you don't necessarily need those specific caps that we install on the CAPBRD products. It should have a very large capacitance (such as the 12 mF cap you have) to store a lot of energy for when the motor current spikes. It should also be sufficiently large to provide a relatively smooth (low ripple) output.

[Snap-On Phil]

The rectifier that was on the machine was wired to the old Heindenhain system. It looks just like the one the capbrdlo has on it. Little 4 tab unit with one differant direction,

[cncsnw]

Do you know what two wires led into the AC terminals of that original rectifier?

Do you know what two transformer taps those AC wires came from?

If so, you can connect the CAPBRDLO assembly to the same two wires, from the same two taps, with the same primary connections feeding into the transformer; and you will get a suitable DC bus voltage out of the CAPBRDLO assembly.

[Snap-On Phil]

No I don’t know how the routing was for the old rectifier ,So you feel the CAPBRDLO should still be fine with the 5nm servos ( stock units ) I don’t have a center tap transformer to use with CAPBRDHI and really don’t want to buy one.

[Snap-On Phil]

I did find a similar machines drawing. This has it appears to be same transformers different controller but same servos. I only see the one rectifier looks to be a 24v ? I marked transformers in light red and rectifier in yellow. I’m just trying to make sure I’m supplying enough voltage to use the ratings of the motors ( as in) torque and voltage with out burning up the CAPBRDLO unit

[cncsnw]

Okay, that helps.

For what it's worth, it is an autotransformer: note that there is a single set of windings, with no isolation between the input and output. Compare the other two transformers, which have two separate sets of windings, with a gap between them (lines in the gap represent the iron core).

It appear that, in your first picture, you have connected 220V (or more likely 240V) between the "0" and "460" inputs, so you are basically running the transformer at half its nominal voltage. That is okay, but you should not count on getting more than 1.5 KVA out of it when you do that.

Running the transformer at half voltage, you get about 90V between "180" and "0". That makes sense.

It appears that the transformer output has two "180" taps, on either side of the "0" taps.

If I were wiring it, I would use a CAPBRDHI assembly, with the diodes connected to the two 180 taps, and the Minus/Common connected to the 0V tap.

I could well be mistaken about this, but it is my impression that you can draw more DC current, for less input AC current, using a CAPBRDHI in this manner vs. using a CAPBRDLO just connected between the "0" tap and one of the two "180" taps.

Also for what it's worth, it appears that the old servo drives were SCR drives with no rectifier(s). They just chop up the incoming AC (by switching off at each zero crossing, and then switching on at some point in the subsequent cycle) and feed the resulting partial wave form to the DC load.

[Snap-On Phil]

but if im putting 124v (my line voltage) in at both 180s on transformer, split should be 124v. so how do i get a voltage @ < 140vdc for the servo motors
will the CAPBRDHI do this?