Capacitors for Furnace in Steel Plant

Thank vinu answers for your valuable comment, it help me alot. Best regard Nguyen Khoa Dung

and sorry, I have another question: What is puspose of high frequence parameter (ex. 500hz) indicated in capacitor for furnaces (Electric arc furnace). Because my rated frequence is 50hz not 500hz ?

See answer #1, particularly the part about "high order harmonics"--the capacitors must deal with (withstand) these.

As the research paper stated EAFs are a rich source of harmonics because of their highly nonlinear characteristics. This means that in addition to the fundamental frequency of 50Hz there may be varying amounts of multiples of this frequency. If the insulation system of the capacitor is not designed to these high frequency pulses then it may break down when exposed to them. Moral of the story is that ordinary (fundamentally rated) capacitors should not be used in this application due to the probability of premature failure.

Hi Vinu,

Great. The link you quoted is really informative.Good answer

Think of the capacitor as a quick release battery. It stores up energy so that when you need it you don't over pull power. The ratchet on demand for electricity can cost millions of dollars. Whatever maximum power the plant pulls for some preset amount of time is what they will have to pay. The power plant must provide for the maximum demand. This max pull with alloted time cost will last for 1 year.

what types of furnace are there. arc, gas or induction

Dear Gud777 The furnace is induction type. The exiting capacitor is high frequency capacitor install at induction furnace terminal for local compensate. can you kindly explance to me the method to calculate the capacity of high frequence capacitor, and what is the defferent to ordinary capacitors (50hz capaccitor) ?

I have to say that i am just a hobbyist and no expert about electricity, so i am not capable to advice you in right directions, but as now you have tell us better information on your problem, and so maybe the experts here can give you better ideas regarding your problem. But Google is my best friend when i need some Information.

Maby this can help. http://www.icrepq.com/pdfs/ZAMORA401.pdf

Is the furnace power supply a variable frequency type? 0-500Hz Induction power supply. If it is, then the capacitors are used to tune the furnace to the power supply like a radio transmitter. In other words, lead and lag on the sine wave according to the melt.

@ rrnut-2:

There is no power supply with a variable frequency type. the power supply for the furnace is 900V, 3 phase, 50Hz, thought 35/0.9kV transformer.

In general, in a co-gen plant with many motors, the problem is too much inductance. They therefore add capacitance so that they can stay on the grid. The grid does not allow for very much swing from perfect balance before they kick you off.