Constant Voltage Transformer
Constant voltage transformer is by definition, a device which can provide a constant output for whatever the input given.
With extensive use of today’s electronic devices, the use of CVT(constant voltage transformer) is getting prominent.
Having a constant or a more stable voltage is extremely necessary for the modern sensitive electronics
So CVTs should be capable of handling the both ends of supressing the high voltages and boosting up the low voltages to meet the defined value.
is there such thing called a perfect CVT? NO…
Would there be any in the future? Nothing is impossible.. so “yes” can be the answer J but I guess NO! for perfect CVT.
What is a perfect CVT?
Perfect CVT should be capable of providing the constant and regulated voltage, regardless of the input level.
And also since the name has “Transformer” in it, it should be only the transformer itself handling this regulation. Not some electronic components or some servo mechanism.
Apparently the todays so called CVTs are mostly the voltage regulators with inherited capacitive circuitry or some tap changing servo system.
So they can be called as “CVPS”-constant voltage power supplies.
So how close to the perfect we can be.
Obviously we cannot build a transformer to provide constant output regardless the input.
But still we can be able to design a transformer which can give a constant output for a particular range of input.
And then again, if we are going to use only the transformer itself without any other peripheral electro mechanical components, it would be impossible to achieve a “flat” output.
But we can make the rate very closer to the flat.
So how to make a CVT..
Here we have two methods.
First and the most obvious method is to have an extremely low slope for input/output relationship of the transformer.
So the output voltage would be almost same for a very high variation of the input.
Let’s do maths..
You know the equation,
So to make this gradient extremely low,
We have to make Nop/Nip ratio very small.
Of course this can be designed.
But the problem would be the size and the cost of this transformer.
It would get bulky and heavy.. and apparently cannot afford.
So what is the second method.
Second method is to achieve a quasi-sinusoidal output like below.
So for a given input range, output wave form would be flat.
How this can be achieved using only the transformer.
Well that is the secret…
This can be achieved by introducing a non-linearity to the flux path.
See below purple line. That is the input/output relationship of a prototype transformer which we are developing.
Got the point?
We have identified a method to make the curve flat during a certain range of input.
Patent is on the way… that’s all I can say right now regarding CVTs..