Rectifier and parallel ac sources

In summary, the conversation discusses the possibility of connecting two AC sources in parallel to achieve a 220 V DC output without using a transformer. The idea of using a rectifier with a thin wire diode is proposed, but the complexity of designing a rectifier is mentioned. The conversation also touches on the importance of considering input and output voltages, ripple, and diode parameters in such a setup.
  • #1
abdo799
169
4
I am new to engineering so i might not understand the concept well , but i want an ac source to provide current only in one way , so i can connect them in parallel.
I have 2 AC sources one with a 100 V output and one with a 120 V output , i need to connect them in parallel so i can get a 220 V dc ( i can not use a transformer, i need to connect them in parallel), so will the rectifier make it possible to connect them in parallel (YES or NO )
the thing is i have a very very tight space, very tight i can't even fit a bridge rectifier, i don't really care about the parameters or ripple now, i just need to know is it possible to make a rectifier just from a simple wire-thin diode?
I read about the ripple , and this can be fixed later in the main wire ( the 2 sources are connected to in parallel ) where we have a lot of space. Right now, I just need to have a 220 V in the main wire
 
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  • #2
Design of a rectifier is a complex procedure. You need to know the input side and the output side parameters first. Also the type of component you going to connect to the rectifier. The type of DC required etc.

I can't understand exactly what you are asking but rectifiers certainly don't come within semiconductor packages. You have to design a rectifier with capacitors and semiconductor devices.
 
  • #3
darkxponent said:
Design of a rectifier is a complex procedure.

Not necessarily. In its simplest form, a rectifier can be just a diode, like a 1N4148 signal diode.

abdo799 said:
I am new to engineering so i might not understand the concept well , but i want an ac source to provide current only in one way , so i can connect them in parallel.
so question number 1) i know i can't connect ac sources in parallel , what if i used a single phase rectifier on each one turning it to a dc ?
2)i 've searched everywhere and still didnt find a conclusive answer, How small or thin a single phase rectifier can be ?, if it's made of a certain semi conductor material can i get it and make it as thin as a copper wire and weld it like it's a sector of the wire ?

If you could describe what you want to do in more detail, we can outline some of the diode parameters you will need to take into account (like forward current, reverse withstand voltage, etc.). What input and output voltages are we talking about here? And how much ripple can you tolerate on our output "DC"?
 
  • #4
I don't know about this 1N4148 but i have never seen a practical rectifier with single diode. The simplest one i have made was of 2 diodes(centre tapped) and 2 capacitors.

And in most cases i have used additional ICs
 
  • #5
Why do you say you can't connect AC in parallel? If they both come from the AC mains you certainly can. If they are from different sources that could be out of phase (like 2 generators) then they in general cannot. A full wave rectifier can be made from 4 diodes. If you need to step up or down the voltage you'd need a transformer on the front end.
 
  • #6
omega_minus said:
Why do you say you can't connect AC in parallel? If they both come from the AC mains you certainly can. If they are from different sources that could be out of phase (like 2 generators) then they in general cannot. A full wave rectifier can be made from 4 diodes. If you need to step up or down the voltage you'd need a transformer on the front end.

I believe the part of your quote that I bolded is why he cannot.
 
  • #7
abdo 799, Mentor berkeman is exactly correct: with such a vague description it’s not useful to try to advise or help you.

Observations:

Yes, AC sources can be connected in parallel; it is done all the time. I myself once installed, tested, and delivered an Uninterrupted Power Supply (UPS) consisting of five separate three-phase, 60 Hz power converters, each one providing 450 KVA, for a total of 2.25 MVA. All that is required is to first ensure their voltages and phases are exactly the same. Connected in this manner they all share the load equally.

If you have multiple AC sources (you have not actually described exactly what you have, or what you would like to do) yes, you can rectify their outputs and then combine them. But it is absolutely imperative they are exactly the same voltage before connecting them together. Once that was done, you could apply that DC source to an inverter which converts DC to AC.

Comment:

AC generators can be connected in parallel. The same requirements as above apply: their voltages and phases must be the same. This is done routinely in some installations for automatic (uninterrupted) redundancy.
 
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  • #8
Bobbywhy said:
abdo 799, Mentor berkeman is exactly correct: with such a vague description it’s not useful to try to advise or help you.

Observations:

Yes, AC sources can be connected in parallel; it is done all the time. I myself once installed, tested, and delivered an Uninterrupted Power Supply (UPS) consisting of five separate three-phase, 60 Hz power converters, each one providing 450 KVA, for a total of 2.25 MVA. All that is required is to first ensure their voltages and phases are exactly the same. Connected in this manner they all share the load equally.

If you have multiple AC sources (you have not actually described exactly what you have, or what you would like to do) yes, you can rectify their outputs and then combine them. But it is absolutely imperative they are exactly the same voltage before connecting them together. Once that was done, you could apply that DC source to an inverter which converts DC to AC.

Comment:

AC generators can be connected in parallel. The same requirements as above apply: their voltages and phases must be the same. This is done routinely in some installations for automatic (uninterrupted) redundancy.

i edited my question and tried to be more clear , thanks
 
  • #9
abdo799,

Here on Physics Forums we have a rule about responding to inquiries regarding dangerous activities. YOU seem to be the danger here. I hesitate to encourage you to take any action at all. Please DO NOT tamper with any electrical equipment without some competent assistance. You are clearly not competent to do this alone.

CAUTION! We CANNOT connect a 100 VAC source in parallel with a 120 VAC source. If you tried it there would be a huge current inrush from the higher voltage unit and the setup would generate maximum smoke!

What gives you the idea you could parallel two AC sources and expect the algebraic sum of their voltages? This is wrong: even if they would not burn from over current, when one wants to add voltages they are connected in series, and NOT in parallel.

You clearly have no idea of how a rectifier functions, or how it can be utilized. Do you really desire 220 V dc as your output, or was that a typographic error and you meant 220 VAC?

Where is your competent electrician? Who is in charge where these units are located? Have you consulted with the manager or supervisor? You risk fire, equipment damage, and even bodily injuries if you proceed without professional guidance. Please hire some qualified electrician or engineer to help you.

WARNING! Electric currents can injure or kill humans, damage equipment, and start fires! Remain safe and please remember, this kind of electric power can kill!
 
  • #10
abdo799 said:
i edited my question and tried to be more clear , thanks

First of all, please do not go back and edit earlier posts. That makes the thread very confusing. You should have just posted a follow-up post that explained the extra details.

And as Bobbywhy points out, your new details make it apparent that you should NOT be working with high voltages. You have very little understanding of electricity so far (as evidenced by your belief that you can put AC voltage sources in parallel to increase the resulting voltage), and the voltage levels you describe are definitely a shock and fire hazard.

Thread is closed. Please seek out a competent local electrician to help you with your project.
 

1. What is a rectifier?

A rectifier is an electrical device that is used to convert alternating current (AC) into direct current (DC). This is done by using diodes, which allow current to flow in only one direction.

2. What is the purpose of a rectifier?

The purpose of a rectifier is to convert AC power into DC power, which is necessary for many electronic devices to function properly. Without a rectifier, the current would continually change direction, making it difficult to power devices consistently.

3. What are the different types of rectifiers?

There are two main types of rectifiers - half-wave and full-wave. Half-wave rectifiers use a single diode to convert AC to DC, while full-wave rectifiers use multiple diodes to achieve a more efficient conversion.

4. What is a parallel AC source?

A parallel AC source is an AC power supply that is connected in parallel with another power source, such as a battery or generator. This allows for a continuous power supply in case one source fails or needs to be shut down for maintenance.

5. How does a parallel AC source work with a rectifier?

In a parallel AC source system, the rectifier is connected to the AC source, converting the AC power into DC power. This DC power is then combined with the output of the other power source, providing a stable and reliable power supply to the connected devices.

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