Half Wave Controlled Rectifier

[mufcforever7]

Please help to provide me a complete circuit for the Half Wave Controlled Rectifier. I have searched many times in the internet but i could not find any complete circuit wif the firing circuit to fire the SCR.

 

[Boncuk]

Hi,

as the term "half wave" suggests you just use one half wave of the AC to rectify.

Here is a circuit of a half wave rectifier.

Boncuk

 

[MrAl]

Hi,


I think he means a 'controlled' rectifier, which uses SCR's instead of diodes and they are only turned on as needed by the load, and the turn on point is determined by the control circuit, which is what he seems to be looking for.

 

[Boncuk]

Sorry for the misunderstanding.

He probably meant something like that.

Boncuk

 

[mufcforever7]

thx u very much Boncuk and MrAI for helping me out!!!

im looking for something similiar like the SCR. How do we turn on the SCR? Izit using variable resistor?

Please guide me...

 

[MrAl]

Hi,

The SCR gate voltage isnt that accurate so you can not really depend on turning it on using the gate characteristics as the backbone for the design. Usually some sort of trigger circuit is used to fire the gate and that is what turns the SCR on. It can be a short pulse and then turn off until the next required firing of the SCR.
What is it that you are trying to build?

 

[mufcforever7]

hi MrAI,

actually i am building tis half wave controlled rectifier to convert AC supply to DC. After that the DC will drive a dc motor. i really cant quite figure out how to build this circuit...

Can you please help me on this?

Thank you very much!

 

[Reloadron]

hi MrAI,

actually i am building tis half wave controlled rectifier to convert AC supply to DC. After that the DC will drive a dc motor. i really cant quite figure out how to build this circuit...

Can you please help me on this?

Thank you very much!

I am missing a few things here. How large is this DC motor as in how much current does it draw and what is the voltage of the DC motor? I don't understand why Half Wave is mentioned? Are you trying to vary the motor speed of a large DC motor using SCR control?

Maybe if you could explain in detail, including voltages and currents exactly what you want to do this would go much, much better.

Ron

 

[MrAl]

Hi again,

Yes that would help a lot thanks Ron.

 

[mufcforever7]

Hi Ron,

im using this half wave controlled rectifier to convert AC supply to DC and to control the speed of a saperately-excited dc motor.

im using half wave controlled rectifier is because required by the spec...

Please guide me Ron and MrAI.

Thank you!

 

[MrAl]

Hello again,

So what you need is a circuit that can fire the SCR and vary the duty cycle so the motor changes speed?

 

[mufcforever7]

hi MrAI,

yea yea i nid a circuit that can fire the SCR and vary the duty cycle to change the speed of motor...

thx u!

 

[Mr RB]

Google for "SCR drill speed controller schematic".

 

[mufcforever7]

hi MrAI,

do u have the circuit that can fire the SCR and vary the duty cycle?

Thank you.

 

[4pyros]

Sounds like a DC motor controller

 

[ronv]

Like this?

Deserthound :: SCR Drill Speed Controller

 

[mufcforever7]

Hi every1!

The drill circuit is the full wave rite? I need half wave only...

Pls guide me...

Thx u!

 

[Boncuk]

Every circuit using an SCR provides half waves only!

 

[MrAl]

Hi every1!

The drill circuit is the full wave rite? I need half wave only...

Pls guide me...

Thx u!

Hi,

You can probably take any triac circuit and make it into a half wave'r simply by only firing on one half cycle of the wave. It shouldnt be that hard, or maybe even using an SCR where the triac normally goes. I personally dont like the diac based firing circuits because the diac doesnt turn on soon enough for every low speeds, but you may find it acceptable in your application it's hard to say without knowing exactly what you are using this for.
I have seen circuits posted right here on ET forum for triacs so if someone would be nice enough to search a little for one. One that looked especially nice used a 555 as the main part in the trigger circuit, which provides very nice triac or scr control.

While we are on the subject, why exactly do you want to use half wave control anyway, rather than full wave control?

Boncuk:
Well there are some SCR based circuits that can fire on both half cycles making it full wave. Two SCR's obviously but even a single SCR circuit can do it.

 

[mufcforever7]

Hi MrAI,

I choose to use half wave because it is the requirement... I mainly use tis circuit to convert AC supply into DC for the DC motor...