SCR regulator?

[rshankar86]

dear all,

I am a 3rd year electronics and communication engineering student working on my project of the "design of high current DC variable power supply", with an expected output of range (1-10)A. Regarding this, I have problem in selecting my regulator circuit as I am not using an IC as a regulator( project rules). So as per my guide's advice I have decided to use SCR regulator. Can anyone help me out by giving me ideas about circuit or the circuit diagram itsself if possible.
I am using a bridge rectifier for rectification purpose.

 

[Nigel Goodwin]

An SCR isn't a linear device, so you can't really regulate DC with it - by feeding the raw output of the bridge to the SCR you can alter it's triggering point to alter the amount of power supplied to the load. Note that this will be a very rough pulsed waveform - OK for light bulbs, some motors, and heaters - it's called 'phase shift control'.

Using two of them you can do PWM from a DC source, which is how fork lift trucks etc. used to be controlled.

But really your specification is far too vague to suggest anything?.

 

[Styx]

10A high current....
suppose I am just lucky working with 1000A


Are you trying to make a variable current-source or a Voltage source with a variable current limit (from 1-10A)


if it is the latter I would recomend designing the Voltage stage and put a current-loop around the voltage loop.


Since a circuit will draw only as much current as it needs, if you build a 10A supply at 10V but put a 1k resistor across it, it wont draw 10A will it



BUT if you are after a current-source... well just as duable.
BUT if you could clarify whather it is a Current-source or a voltage-source you want

 

[rshankar86]

its a current source

I am a rookie in this ocean..... i m fascinated and excited by the fact that u are designing a dc current source of 1000 A magnitude .

The primary aim of my circuit is to convert a given AC source into regulated current supply of range say (1-10)A. Ironically, i wanted to make the regulation part a bit different. This is why I decided to use SCR. But now I have realized tat SCR's ripples wont give me a constant dc o/p required.

thank u very much all 4 ur guidance....

Shankar Ramanathan

 

[Styx]

Re: its a current source

I am a rookie in this ocean..... i m fascinated and excited by the fact that u are designing a dc current source of 1000 A magnitude .

The primary aim of my circuit is to convert a given AC source into regulated current supply of range say (1-10)A. Ironically, i wanted to make the regulation part a bit different. This is why I decided to use SCR. But now I have realized tat SCR's ripples wont give me a constant dc o/p required.

thank u very much all 4 ur guidance....

Shankar Ramanathan

Ahh well this is different!!!! IF you are sure you really are after a current-source, (ie sometihng that will produce alot of amps, and obiously some voltage)


At work we have 3 kinds of supply's

1) Power. 45KVA variable freq 3ph power supply
2) High voltage. 400V DC (tunable) with a tunable current-limit upto 40A
3) High current. a 20V DC (tunable) with a tunable current-limit upto 600A

So as you can see what we use as a current-source really is a power-supply but depends on its use

If we set the voltage high enough but set a current-limit it will act as a current-source sitting in current-limit
IF we set the voltage low enough but the current high enough it will act as a voltage source sitting in voltage-limit

With the added infomation abt supplying from AC then Thyristors/SCR are the ideal choice.

How? Fully-controlled rectifier with the firing angle controlled via a current-loop. AND to make it a current-source a nice big inductor, this will also smooth out any current-ripple giving you a current-ripple that is related to inductor size





You will definitly want to use a step-down transformer, what is the highest voltage you perceve you will need (bearing in mind for a current-source to work it's voltage-limit must be in excess of the load voltage)