View attachment 227697

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.

The symbols are wrong. It looks like someone is trying to draw a 3-phase AC, rectified to DC for powering a motor. They are using SCRs for rectification diodes, and they don't know how to draw a Y for 3-phase, or this is from a simulator that doesn't have those symbols so they are 'making do'....

...at least that's my SWAG.

 

The SCR bridge phase angle control units were typical DC motor controllers used in motion control and CNC in the late 70's on.
Max.

 

The symbols are wrong. It looks like someone is trying to draw a 3-phase AC, rectified to DC for powering a motor. They are using SCRs for rectification diodes, and they don't know how to draw a Y for 3-phase, or this is from a simulator that doesn't have those symbols so they are 'making do'....

...at least that's my SWAG.

Okay, now I'm confused. Whom should I believe now ?


Maybe BobaMosfet doesn't take consideration that the symboly whichs is used in there are european.

 

Having worked on many of these drives in the 80's 90's in the CNC field they are quite familiar, I can dig up an old example of a drive, probably.
They are not exclusively euro symbols. But Universal.
Max.

 

Having worked on many of these drives in the 80's 90's in the CNC field they are quite familiar, I can dig up an old example of a drive, probably.
They are not elusively euro symbols. But Universal.
Max.

That would be interesting and it seems that you got knowlege about this. Can you also explain me the reason why a SCR bridge phase angle control is used for a DC Motor ?

And the function of the wire where V1 is placed ?

 

Ohh no, this manuel has more than 700 pages.

So? It's called homework. Use the table of contents and the index to find the chapter that fits your questions.

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.

The output of the bridge is pulsating DC with a ripple frequency that is 6 times the line frequency. This makes for a relatively low peak-to-peak ripple voltage. Changing the timing to the SCR's changes the average value of the DC output voltage, and hence the motor speed.

ak

 

That would be interesting and it seems that you got knowlege about this. Can you also explain me the reason why a SCR bridge phase angle control is used for a DC Motor ?

And the function of the wire where V1 is placed ?

Because it was at the time a simple form of providing variable DC for RPM control, not only is the ripple low, but the mean motor current level has minimum ripple due to the inductive reactance of the motor.
Max.

 

It has gone out of fashion, not because of its lack of efficiency, but because the brushed DC motor has gone out of fashion being replaced by more reliable brushless motors; and because of poor mains harmonic currents.
The circuit is still alive and well in battery chargers, especially those for fork-lift trucks.
Thyristors are extremely reliable devices, with a better ability to withstand surges than IGBTs, and can't get accidentally biassed into a linear region where they dissipate power and fail, and don't have a vulnerable gate oxide.

 

So far every one of Max's comments have been totally correct. And if the TS does not understand what is going on then they were either not listening in class or missed the first three courses. The circuit is indeed totally reasonable, and there is no adequate reason to consider alternate devices. And why have a discussion of fusing on a theory level circuit??? And three phase power is indeed drawn that way. And the TS needs to understand what L1, L2, and L3 are before going any farther.

 

View attachment 227697

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.

This seems like using AC input to power DC motor......Those diodes rectify the AC input and power the motor thats all i can think off

 

This seems like using AC input to power DC motor......Those diodes rectify the AC input and power the motor thats all i can think off

Exactly what it is. Before variable-speed drives, only brushed DC motors could easily be speed-controlled.

 

First, this is NOT a series-field DC motor, because a separately excited field is clearly shown. That inductance "L" s a reactance for filyering the DC to reduce the ripple voltage, OR both the L and the resister "R" may be simulator values for the armature inductance and resistance. So there would not be a manual in existence because this is not a product circuit drawing. In addition, that transformer secondary is not a center tap, but a "WYE" connected winding of the 3-phase transformer.
The requested detailed circuit analysis would be an engineering level report that would cost a fair amount, and certainly not be a free thing.

 

As per posts #16 & #17, it is more likely series compensation winding, commonly seen on larger DC motors which also required a field loss circuit for the shunt winding to prevent runaway in the event of an open field, and possible damage to life or machine.
.The AC PM motors that came after used a 3ph bridge with a six BJT controller after it achieving the same thing, just different motor technology.
Max.

 

As per posts #16 & #17, it is more likely series compensation winding, commonly seen on larger DC motors which also required a field loss circuit for the shunt winding to prevent runaway in the event of an open field, and possible damage to life or machine.
.The AC PM motors that came after used a 3ph bridge with a six BJT controller after it achieving the same thing, just different motor technology.
Max.

That is quite an assumption, about it being a compensation winding, given that it is not labeled as such, and that there is also a resistor, just tagged as "R", and given that there is no additional labeling of them. So it makes more sense that they are either separate components or simulation variables although they are not tagged as such.

 

That is quite an assumption, about it being a compensation winding,

Not really a stretch, it appears to be a symbolic drawing, not details of actual devices, therefore in that style of motor, compensation winding's were common.
It would not be for any control of the motor RPM obviously, as this would be done through the SCR control electronics.
This general diagram was typical of large DC motors used in industry and machining, CNC spindles etc.
Max.