Does any one know some thing about this circuit ? I must wirte a functional analysis. Therefore I got some question:

Frist what is that ? Is that an engine or something ? Are the 6 elemetens there SCR's ? And why they are used ? Is there a better solution instead of using them ? And what is this cirucit exactly doing ?And how can I describe the function of the wire where V1 is placed ? And what does die wire means which is right one the side ? And is T1 a center tap ?


I hope that some is here you know something about this.

 

My limited contribution: the symbol with the "M" belongs to a motor, not to an engine.

I am sure there are "better solutions". Define first to what.

 

Hello,

IE is likely the current through the exitation coil of the motor.

Bertus

 

@atferrari

For a oven. So what could I do to improve the efficiency?

And it seems that T1 is a center tap but I'm not sure, is there some one who can confirm that?

 

Hello,

The used transformer is a 3 phase transformer with a Delta input and Why output going to a controlled bridge rectifier.

Bertus

 

That was how early larger DC motors were driven in many industrial machines, directly off the 3phase supply, very common in the 70's to 90's, even later.
Appears to have a shunt wound field, the controller for this would have a circuit in the event of field loss etc to prevent runaway..
Max.

 

Okay thanks a lot now I know what its. Does someone got the manual? Or something?

And what can we do to proof the efficency? What can we replace. (Usage as a oven.)

 

It's known as a six-pulse fully-controlled rectifier. Still one of the most efficient ways to speed-control a large DC motor.
The main improvements in efficiency would be to use a brushless motor, but the IGBTs in a variable-speed drive have greater losses than the SCRs, higher voltage drop, and higher switching losses because of the higher operating frequency.

How is it used in the oven?

 

General Electric’s SCR Manual, 5th edition, will provide you with all the information required to understand a three phase controlled bridge, and how it relates to DC motor speed control.

 

Ohh no, this manuel has more than 700 pages.

But what I can't understand know is why a DC motor with series excitation (correct me If I'm wrong) is wiring together with a three phase controlled bridge. As far as I know this takes only senes for ac.

Furthermore I searched in the internet, so now I can't understand just the part with T1, L1, L2, L3. This must be a center tap (I'm not sure about this), and could find something that is similar.

Maybe some can explain this parts in short and easy way.

 

It also shows a shunt field, separately excited
That could be a series compensation winding.
The output of a 3ph bridge is 180 hertz ripple, no problem for a DC motor.
The transformer is a delta primary, star secondary.
As per post #6, motor controllers of this nature have always been common for DC motor control.
Max..

 

L1, L2 and L3 are the three live inputs (brown, black and grey wires in Britain and Europe).
T1 is a three phase transformer which looks like this:
Here's a bit more on 6-pulse controlled rectifiers:
https://www.ewh.ieee.org/soc/es/Nov1998/08/CONVERTR.HTM
https://www.electronics-tutorials.ws/power/three-phase-rectification.html
The output ripple frequency is 300Hz on a 50Hz supply, 360Hz on a 60Hz supply, hence "6-pulse"

 

I can't understand just the part with T1, L1, L2, L3. This must be a center tap

T1 is just the designator for the transformer. The line represents the core, not a tap.

 

A 3ph transformer is simply 3 transformers on the same frame/core, it can just as easily be achieved using three separate single phase versions.
You have a star or delta option of connection.
The one in the OP is Delta-Star connected.
Max.

 

I suspect the three-phase version might be cheaper than three single-phase transformers. It will certainly be smaller and lighter.

 

I suspect the three-phase version might be cheaper than three single-phase transformers. It will certainly be smaller and lighter.

It is often done in a pinch, where a replacement is not immediately available etc.
I was once faced with a similar option.
Also it was a effort to point out that in principle, it is derived from three separate circuit devices.
Max.

 

That could be a series compensation winding.

As further explanation, that series compensation winding adds extra field excitation with load.
The number of series winding turns is selected to provide minimum change in motor speed with load change.

 

So far so good. Now I got the knowlegde. But the next huge questions is:

What can we do to improve, the effiency ? The only I can see, is to replace the 6 thyristor to 6 gto's. And add 3ph transformers so that we have in the end 6 of them ? Would this work ? Or you have better ideas ?

 

What would be the point?
Apart from being a bit of a legacy circuit, the method has worked fine and fairly efficiently in the past.
One thing that had to be observed was the use of Rectifier fusing, as power line failures or surges often caused misfiring and destruction of the SCR(s).
Just mainly replaced now with PWM drives and PM.AC motors.
Where does six transformers fit in?
Max.

 

@MaxHeadRoom

This is a good point of view. Now I noticed that it doesnt make sense. But who does the Rectifier fusing look like ? Are they common Rectifier fusing ? Or is there a specific rectifier fusing which was developed for fixing misfiring and destruction of the SCR's ?