What is the calculation process for firing angles in rectifiers?

[daveo91]

Hello

I have recently been covering firing angles in rectifiers at uni. I didn't really understand it in the lecture, and the tutorial questions/one to one with the lecturer didn't help either.

It would also seem that the internet isn't of much help either from a quick Google search and as we now have a coursework question on this subject all the relevant textbooks are out in the library.

So I was wondering if anyone has any good links to resources on rectifiers, in particular on calculating the firing angle.

From what I understand it "can't" be calculated?

 

[jim hardy]

what you need is GE's "SCR MAnual", an exhaustive text on that field. They literally wrote the book that trained generations of engineers. Look for fourth or third edition if you buy one. They're usually on EBAY..

Meantime -have you tried searching on phrase "Phase control thyristor" ?

old jim

 

[NascentOxygen]

From what I understand it "can't" be calculated?

Such a sweeping statement, it's bound to be wrong for some cases, at least. What are the factors that have led you to conclude that it can't be calculated?

 

[Windadct]

I am assuming you mean what should the firing angle be for a given load? This is actually pretty difficult to calculate - they are almost always dependent on a (real time)control feedback loop - for ether constant current output or constant voltage. Light dimmers are the biggest users - but this is not a precise application and you do not set by phase angle - you adjust by light.

There are many factors affecting the energy throughput a Thyristor controller: The Source, The thyristors themselves change with temperature, and the load - all vary over time.

For Example if you build a basic DC supply with thyristors ( controlled rectifier), and have the firing angle set with something like a potentiometer ( e.g. no realtime control) - you set the phase angle to get a voltage under no load, then you use the DC supply - and the DC voltage is no longer at the set point.

I would guess - you could theoretically define ALL of the circuit, and calculate a necessary phase angle - but IMO this would just be an exercise - and I can not think of any pracatical application.

And yes the GE SCR Manual is the Bible - Looking through this now (Chapter nine) it has mostly reference graphs for relating Load Voltage to Phase control ( based on source voltage) - but also with notes concerning the type of load. And they reference 15 different typologies. Note- reference to my comments above the section discussing calcuating phase angle being just an exercise - The Manual has 9 pages out of a 600 page book - discussing these calculations...

 

[alphysicist]

Hello, as a scientist, I can understand your frustration with trying to understand the concept of firing angles in rectifiers. To help clarify, the firing angle refers to the delay between the time the input voltage reaches its peak and when the rectifier begins to conduct current. This delay is controlled by the gate signal in a rectifier circuit.

To calculate the firing angle, you will need to understand the characteristics of the input voltage and the rectifier circuit. This includes the type of rectifier (half-wave or full-wave), the load resistance, and the type of load (resistive or inductive). With this information, you can use mathematical equations or simulation software to determine the firing angle.

I would recommend consulting your textbooks or reaching out to your professor for specific calculations or examples related to your coursework question. Additionally, there are many online resources available that provide step-by-step explanations and examples of calculating firing angles in rectifiers.

I hope this helps in your understanding of firing angles in rectifiers. Keep exploring and asking questions to deepen your knowledge in this area. Best of luck with your coursework!