Power Factor Improvement

What if he needs distributed heat, it would be a big job re wiring heater bank to switch off 3/4 of the panels and still maintain a heat spread.

Auto switching capacitor banks sound ok to me,

Alternativly you could use phase control to a transformer to lower the output voltage to the heaters, could be another power factor problem there.

These features were not in the original post.

True but you would expect that a bank of infra red heaters would be heating an object as a bank not odd spots here and there, it brings to mind paint drying cabinets.

I thought my observation was valid.

Without a more concise definition of the problem by the Original Poster, the forum might never know for certain.

Gee that was a long time ago, nice to here from you.

Care should be exercised when designing the capacitor bank because of harmonics generated by the thyristor drive. Merely slapping capacitors in the supply may cause problems. Get someone who can measure the harmonics over the range of your power requirements and tune the bank to supress the relevant frequency.

Use "whole cycle" switching . . .

For 75% power turn the heaters OFF for every fourth whole cycle . . .

For 50% power turn the heaters OFF for every other cycle . . .

And so on . . . You may run into a problem of "flicker" . . but your power factor will be 100%.

O.

One thing that puzzles me here, AFAIK all short wave infrared heaters have a purely resistive load impedance. Why does the OP have a capacitor bank at all here? Similarly, if the only reactive impedance here is the inductance and capacitance of the cabling then with a power distribution frequency of 50 or 60 hertz what is changing the phase angle of the current away from a purely resistive angle. I'm certain that the cable run is not several kilometers long to make transmission line effects a factor. I suspect that there are either inductive motors powering fans that should not see this variable waveform or that the power factor instrumentation is not reporting a true response.

There is something more happening here. I suspect the OP is honestly telling us all that they know, but something is missing here.

I am inclined to use IGBT as the powerfactor claimed is above 0.93

The other switching options do not work correctly as the inrush current in Infrared lamps is almost 11 time more as hot and cold resistance is different.

All other comments on different answers are good.

I thank all the experts for sharing their experinence.

Can anybody suggest a good source for IGBT based controllers in the required range having reliability experience.

Whomever is telling you they can improve your power factor to .93 using an IGBT based PWM controller is not telling you the whole truth, a common game in that industry. You will spend 5X - 10X the cost of the controller for an IGBT based system and then you will introduce more harmonics and distortion power factor instead of displacement power factor. The net gain for you will be nil, the net gain for them is tremendous.

What MOST other people do in this case is to use a "Combination" SCR controller, one that uses phase angle control at the initial start up to control inrush from the high hot-to-cold coefficient of resistance difference, then change over to zero-cross variable time based control for running in order to avoid the power factor and noise issues. The cheap SCR controller mfrs do not offer this, you need to be speaking to those that offer higher quality controllers and know what they are doing.

At 0% voltage, the power factor will be zero. So why is the feature <...the power factor goes to about 0.55...> actually considered a problem locally?

You may think of turning off alternate infra heater and using controller @100%

Of course temp profile is also important.