Improve Power Factor with Zero Cross Transformer Mode


Welcome. I'm Cory Watkins, President of Control Concepts. Today we're here to discuss how you can improve power factor for transformer-coupled loads.

Now, traditionally, zero cross SCR controllers are used for resistive loads. This is because zero cross operation reduces harmonics and maintains existing power factor. However, if a system design requires an isolation or step-down transformer, you would need to switch to phase angle operation in order to prevent saturation of the transformer. Switching to phase angle operation has the advantage of improved power control, but suffers from both increased harmonics and degraded power factor.

Today, with the advent of digital SCR technology, we are able to combine phase angle and zero cross firing technlogies into a hybrid firing mode that we proudly introduce as "Zero Cross Transformer Mode," or ZCT Mode. 

This technology allows you to maintain a power factor of greater than 0.9 from 50-100% command signal, thereby eliminating the penalties you may see from your utilities.

So you may be wondering, are you a good candidate for ZCT Mode? Good candidates are those who are:


  • Looking for improved power factor
  • Have transformer-coupled loads
  • Either require high thermal inertia, or require less stringent process control


So in summary, Zero Cross Transformer Mode can improve power factor by maintaining a power factor of 0.9 or greater from 50-100% command signal for transformer-coupled loads. 

If you'd like to learn more or talk to one of our application engineers about your project, give us a call at Control Concepts. Thank you.