Tuesday, May 24, 2016

Pellet burner controller code

My pellet burner controller code become open source. The code is in programming language C. I post it at the GitHub: https://github.com/canji/Pellet-burner-controller

Comments in the code are on the Serbian. I don't have time now to translate it. If someone need help understand the code, please contact me

I have big omission in my previous post about pellet burner controller. Pellet burner expert which I cooperated is Miodrag Cvejin. Big thanks for him!

Tuesday, May 17, 2016

Diesel generators

Sometimes at my job I work with diesel electric generators. As a testing engineer I perform inspection and test of it. For testing we use a mobile load bank. Our mobile load bank is just resistive and it looks like giant heater. It has bank of heater and fan. Its maximum load is 1MW. 

Diesel generators aren’t complex machines. They have two parts. One is a diesel engine and second is an electric generator. 

From electrics and electronics stuffs a diesel engine has lots of sensors. The most typical is for an oil pressure and a temperature, a coolant level and a temperature and a pick-up for speed. 

A generator gives the sin wave output voltage with specified voltage amplitude and frequency. In our case this is always 400V between phases and 50Hz. 

The generator frequency depends from a diesel engine speed. We control frequency by controlling the diesel engine speed. Because most of generators are four pole electric machines we need 1500 rpm for frequency of 50Hz. 

Most of diesel generators that we test are older than me. This old diesel engines have fixed fuel injection. Because of this its frequency varies with changing a load. As we gain load the frequency goes down. Most of old diesel generators can take no more than 80% of load and for this load frequency goes down for 1Hz. 

New generation of diesel generators has an electric control fuel injection and them frequency is perfect 50Hz all the time. Just when we apply high jump of load the frequency changes a little. This change depends from a PID controller for speed control. When we apply high load, for example form 0% to 75%, frequency goes down because of suddenly high load. Depends of a PID controller it can be slow comeback to the 50Hz without over frequency or quick come back to the 50Hz with some peak of over frequency. 

For a generator voltage control a generator has voltage regulator. A generator is synchronous electrical machine and its output voltage depends from a magnetic field in a rotor. Voltage regulator is uses to control that magnetic field. It works as controlled AC DC converter. With DC voltage output it controls magnetic field in a rotor. 

Also as frequency, old diesel generators has fixed voltage regulator. Output voltage changes with changing frequency. In some case voltage goes down when frequency goes down and in some cases are oppositely. 

New generation of diesel generators has an electric controlled voltage regulator and output voltage is always perfect 400V. 

I reconstructed one voltage regulator and this interesting electronic story will be in the next post. 

Wednesday, May 11, 2016

Typical holiday

Adam and Milica

Last two weeks I was in the Brus. This is typical holiday for my family. The Brus is hometown of my wife Milica. This is a small town near Serbian famous mountain Kopaonik. There we always have a nice time.

My favorite sport activity is road bike climbing to the Kopaonik. There are four roads for climbing to the Kopaonik. I think every climb is the first category in cycling. I try every of four roads and my favorite climb is through “Kriva Reka” village. 

There are many interesting places near the Brus. Mountain Goc is also beautiful. Food is excellent there. In a future I will write more detailed about the Brus.

Top of Kopaonik mountain

Some pictures from previous holidays:  

My car preparing for the trip

Top of the hill above the Brus 

Bike climbing on the Kopaonik through "Kriva Reka" village

The old castle "Koznik" near the Brus