The primary responsibility of a power supply is to convert AC voltage to DC voltage. Most electronic devices you plug into the wall require this. But when linear supplies have a low power factor, it can introduce harmonic current into the system.
With enough devices hooked up to a grid, the cumulative effect of this can lead to significant harmonic distortion, especially on industrial machines that draw more power.
Power factor correction (PFC) power supplies provide clean and efficient power for motor control. Power factor improvement is so important because harmonic distortion can lead to overheating, unstable equipment, and even motor failure.
Achieving proper power factor correction can protect the integrity of your devices and ensure that you are not drawing too much power on any load. In addition, it can prevent you from paying hefty electric bills for your facility.
Here, we’ll explain Power factor correction in more depth and go over ADVANCED Motion Controls’ PFC power supply capabilities.
What is Power Factor?
Power factor is defined as the ratio of the real power to the apparent power in a circuit. Essentially, real (or active) power is the amount of power that is actually usable, while apparent power is the vector sum of real power and reactive power in a circuit. A higher power factor means more of the power is real power.
This phenomenon of real power and reactive power occurs due to the phase difference between voltage and current. It’s an inherent result of inductance and capacitance in any AC circuit. This frequent lag causes results in only some of the power being useful. Correcting the power factor reduces the power that is wasted.
The apparent power is often expressed as a complex number, with real power as the real component and reactive power as the imaginary component. This leads to the misconception that reactive power is “imaginary.” The reactive power is real in the sense that it exists, but it is unusable for any actual work.
Correcting the Power Factor
An ideal power factor would be 1.0, but it usually falls somewhere between 0 and 1.0. Because inductance is always changing with the load, maintaining a perfect power factor of 1.0 is impractical and often impossible.
Achieving a relatively high power factor is desirable, however. It’s generally recommended that electronic devices reach a power factor 0.8 to efficiently utilize power. The US department of Energy calls for a power factor of at least 0.9 in their Voluntary Energy Star Guidelines. The EU has legislation regarding power factor standards for classes of electronic equipment. Countries such as China, Japan and Australia have followed suit.
Why is correcting the power factor such a concern? Conventional diode-bridge-rectified AC/DC converters have several shortcomings as compared to converters with PFC. As previously mentioned, uncorrected power factors raise the risk of harmonic distortion in the current and voltage cycles when non-linear loads are connected to the system. Many electrical components rely on precisely controlled current and voltage to function properly, but harmonics polluting the power line results in voltage fluctuation, which limits the power and speed range of motor drives. In short, harmonic distortion can cause devices to become unstable, overheat, or even fail altogether.
But even if you don’t care about correcting your power factor, the electric company does; they are the ones who must compensate for the reactive power losses, and they won’t do it for free.
Residential locations are only charged by the power companies for the real power they consume, so correcting the power factor at home shouldn’t be a concern. Industrial and commercial facilities, however, can be charged extra for not correcting their power factors. In some cases, they are charged for their reactive power if it exceeds a certain percentage of the real power consumed.
There are plenty of power factor correction systems on the market, including power factor correction convertors, automatic power factor controllers, and boost PFC converter circuits.
The advantages of power factor improvement include:
- Greater efficiency reduces electricity costs
- Cleaner power on factory floor
- Cleaner voltage output over a wide range of inputs
- Protection for valuable equipment
- Better machine reliability in difficult conditions
- No extra surcharges from the power company
PFC power supplies could generate an ROI in a very short amount of time by properly using electricity to its fullest potential and protecting the integrity of your motor.
Capabilities of AMC’s PFC Power Supplies
At AMC, our primary business is still servo drives and controls. However, as a convenience to our customers we have long maintained a line of unregulated power supplies that work with our servo drives.
Recently, with the demands of global machine builders we’ve started manufacturing new power supplies designed to achieve power factor improvement, improve performance and ensure consistent operation regardless of the local power company’s voltage levels and quality.
- Input Voltage 100-240VAC +/-15% @ 50/60Hz +/-5%
- Nominal output 375VDC +/-2%
- Continuous DC Output Current 6.4A @ 240VAC input
- Efficiency at full load 97%
- Power factor >0.95 @ 250W, up to >0.99 above 250W
- Leakage current < 180µA @ 240VAC/60Hz
- Built-in shunt regulation to handle excess regeneration
- Min class A EMI without external line filter
- 5kV isolation to chassis/PE
You deserve the best for your application. If you’re concerned about power factor for your application, consider using one of our new PFC power supplies. Contact us for part numbers and availability.