Rectified AC through an AC transformer

In summary, it is possible to rectify an AC signal and run it through an AC transformer, but care must be taken to avoid bias and saturation.
  • #1
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Like the title says, I am wondering if it is possible to rectify an AC signal and run it through an AC transformer. The rise and fall in voltage still exists so it should work, or are AC transformers made specifically for an AC signal and other information needs to be taken into account?
 
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  • #2
Yes. As long as the transformer is not driven into saturation and the current limits are not exceeded. AM radio transmitter modulator transformers carry the DC current of the final amplifier, so I'm sure it can be done.
 
  • #3
AdamK9 said:
Like the title says, I am wondering if it is possible to rectify an AC signal and run it through an AC transformer. The rise and fall in voltage still exists so it should work, or are AC transformers made specifically for an AC signal and other information needs to be taken into account?

You can, but for a 50/60Hz waveform, you will get somewhat more losses through the transformer. Quiz Question -- why?

Why are you wanting to put a rectifier before a transformer?
 
  • #4
It depends on the transformer.
There is a large DC bias; the average of the rectified signal.
AC power transformers are not made for this; the core will saturate.
A series capacitor between the rectifier and primary will eliminate the bias.
 
  • #5
Phrak said:
It depends on the transformer.
There is a large DC bias; the average of the rectified signal.
AC power transformers are not made for this; the core will saturate.
A series capacitor between the rectifier and primary will eliminate the bias.

Phrak is correct. While transmitter modulation transformers are designed to have a DC bias, power transformers are not. I don't think a small current would cause much trouble, but what you are trying to do might. It all depends on the transformer and how much DC current you will be putting through it.
 
  • #6
Thanks for all your help. I am wanting to rectify it ahead of time because i want to step up the voltage to about 20000v with a power transformer and since high voltage diodes tend to be more expensive than low voltage ones i was wondering if it was feasible to rectify ahead of time, but it doesn't sound like it will work in this situation since its going to be pretty high current on the primary
 
  • #7
AC power transformers are designed to be cost-effective to the manufacturer, meaning that they minimize the material cost, iron and copper in particular. The number of turns in the primary is minimum, which pushes the peak core magnetization field close to 1.5 tesla for the maximum peak (not RMS) primary voltage. This peak AC excitation is proportional to the peak input voltage divided by the primary inductance. The only way to reduce this peak excitation is to reduce the input voltage. A DC current will produce a DC offset magnetization in the core and push the peak AC + DC magnetization into a very non-linear magnetization, unless the AC excitation voltage is reduced. In short, for power transformers, there should be no DC current on the input. Power transformers designed for rectification, full wave bridge or full wave center tap, have no average DC current in the secondary, but a half wave rectifiier secondary will, and this could also bias the magnetization, but the manufacturer has probably taken this into account.
 
  • #8
AdamK9 said:
Thanks for all your help. I am wanting to rectify it ahead of time because i want to step up the voltage to about 20000v with a power transformer and since high voltage diodes tend to be more expensive than low voltage ones i was wondering if it was feasible to rectify ahead of time, but it doesn't sound like it will work in this situation since its going to be pretty high current on the primary

I hope I'm not misreading your post but it sounds like you have a misunderstanding of basic transformer function. Rectifying the primary will not give you DC on the secondary. You will only get the AC component on the secondary. If I wanted 20kv DC, I would just use a fly-back transformer and rectifier from an old tv set. But please be careful. You can be killed. I have no way of knowing if you have the necessary background to be dealing with such high voltages. From reading your posts it would seem that you do not. If such is the case then I would strongly recommend that you not continue with this project.
 
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  • #9
AdamK9 said:
Thanks for all your help. I am wanting to rectify it ahead of time because i want to step up the voltage to about 20000v with a power transformer and since high voltage diodes tend to be more expensive than low voltage ones i was wondering if it was feasible to rectify ahead of time, but it doesn't sound like it will work in this situation since its going to be pretty high current on the primary

Place a voltage multiplier following the transformer. The multiplier requires AC input. You can look it up. It's just a bunch of capacitors and diodes. The current is low, and the impedence is high. But you can get your voltage if it doesn't arc-over. I would select the diodes first and the transformer, dependent on available diode voltage, second.
 
  • #10
You cannot rectify an AC signal and then pass it through a transformer and expect DC on the other side.
If you feed pulsing DC into the primary of a transformer, you will get AC on the secondary of the transformer which will still need rectifying to get DC. This is apart from the saturation effects mentioned earlier.
 

1. What is rectified AC through an AC transformer?

Rectified AC through an AC transformer is the process of converting alternating current (AC) to direct current (DC) using an AC transformer. The transformer converts the high voltage, low current AC power into low voltage, high current AC power, which is then rectified into DC power.

2. How does an AC transformer work?

An AC transformer works by using two coils of wire, a primary coil and a secondary coil, wrapped around a core. The primary coil is connected to an AC power source, while the secondary coil is connected to a load. As the alternating current flows through the primary coil, it creates a magnetic field that induces a current in the secondary coil, transforming the voltage and current levels.

3. What is the purpose of rectifying AC through an AC transformer?

The purpose of rectifying AC through an AC transformer is to convert the AC power into DC power, which is needed for many electronic devices to function. This process also helps to regulate the voltage and current levels, providing a steady and reliable power supply.

4. What are the advantages of using an AC transformer for rectification?

Using an AC transformer for rectification has several advantages. It allows for the conversion of high voltage, low current AC power into low voltage, high current DC power, which is more suitable for electronic devices. It also helps to regulate the power supply, providing a steady and reliable source of power.

5. Are there any disadvantages to using an AC transformer for rectification?

One potential disadvantage of using an AC transformer for rectification is the cost. AC transformers can be expensive, especially for larger power applications. Additionally, the process of converting AC to DC through an AC transformer can cause energy loss, reducing overall efficiency.

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