Electrical Testing
Power Quality Improvements Do Save Energy

Power Quality Improvements Do Save Energy

Adding power factor correction capacitors will enable motors to use less energy and run cooler.

One way companies reduce their electric bill is by installing power factor correction capacitors at the service. Often, those capacitors assume a “set it and forget it” role; they’re installed, and nobody bothers to see if they’re still functioning a year later.

Although this does eliminate the utility’s power factor penalty, you could still have low power factor at the points of utilization.

Image Source: Echoray/Wikimedia Commons

The reality is each of those 10 hp motors on your conveyors is, unless corrected at the motor, more than likely operating at lower power factor than you really want. They add up, too, giving you a power vampire. Add to these losses the power factor losses you have from the 400 hp air compressor motors, various fans and pumps, mixer motors, and so on. It becomes a serious portion of your total energy waste.

The solution is to add power factor correction capacitors to each of these motors (those without VFDs); the investment will pay off, probably in only a few months. And your motors will not only use less energy, but also run cooler.

You can take this to the next level by installing VFDs that are power factor corrected and harmonics corrected.

And that brings us to another power quality issue that affects your energy bill: high harmonics. Solutions include installing harmonic filters or traps, putting high harmonic loads on their own transformers, replacing high harmonic lighting ballasts (maybe upgrading the whole system to LED), and making sure you have proper bonding per Art. 250, Part V of the NEC (never ground where you should bond).

Phase imbalance (the phases differ greatly in voltage and/or current) is another energy waster, especially if motor loads are on those imbalanced circuits. Lighting is a single-phase load; to avoid contaminating three-phase systems with imbalance, put lighting systems on their own transformers and panels. Your three-phase motors will thank you for this (they will run cooler and last longer if not subjected to imbalance).

To keep tabs on how well (or not) these efforts are paying off:

  • Conduct baseline thermography before making any changes, then repeat the thermography after each change has been made. This gives you a new baseline, in addition to verifying that your efforts have produced results.
  • In addition to the thermography step above, do the same thing with a battery of power quality tests (including power factor and waveform analysis) using a portable power quality analyzer.
  • Install a power monitoring system, and ensure that it monitors specific loads rather than just your main distribution. At a minimum, you want it monitoring your large motors for single-phasing, decreasing power factor, rising current consumption, and other issues that indicate maintenance attention is needed.
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