Line Interactive vs. Double Conversion UPS

Line Interactive vs. Double Conversion UPS – Which One’s Best?

A client once purchased a line-interactive UPS system to protect their sensitive metrology units. Still, their units continued to fail from power problems. Why? Because a line-interactive system does not protect against all nine common power anomalies.

Although we do sell line-interactive UPS systems, we rarely recommend them. So why do some clients continue to purchase them?

Simple. They are often cheaper in the short run.

However, as a smart UPS consumer, you must look past the initial price tag. UPS systems are instrumental in keeping your mission-critical equipment online. With such an important job, a lower price should never outweigh a unit’s total value.

Line-Interactive vs. Double Conversion – What’s the Difference?

Line-interactive – These UPS systems monitor incoming voltage from the utility. If it detects a power loss or anomaly, it will boost or decrease utility power by allowing it to pass to the protected equipment or by running on battery power.

This model is ideal for applications where the utility power is fairly clean. If you have a computer at home or in a small office that you’d like to afford some reliability, you can often find a line interactive UPS for an affordable price.

Online double-conversion – These UPS systems provide your facility the highest level of protection by isolating the equipment from raw utility power. The system works by converting power from AC to DC and then back to AC.

This unit is the only UPS that provides power with zero transfer time to the battery, making it ideal for sensitive equipment. That’s why it’s the best option for any facility with mission-critical equipment and in locations with poor power conditions.

Additionally, an online, double conversion UPS has an internal static bypass, ensuring that if your UPS experiences a catastrophic failure or requires maintenance, you may be able to keep your critical loads online during repair or replacement.

Head-to-Head: Which UPS Comes Out on Top?

The true measure for any UPS system is how well it can protect against the nine power anomalies.  Here’s a brief description of the nine common power anomalies:

  1. Power failure – A total loss of utility power.
  2. Power sag – Short term low voltage.
  3. Power surge (spike) – A short term high voltage more than 110 percent normal voltage.
  4. Under-voltage (brownout) – Reduced line voltage for an extended period of a few minutes to a few days. This often happens during the summer months when people set their air conditioners higher than normal.
  5. Over-voltage – An extended period of increased line voltage for a few minutes up to a few days.
  6. Electrical line noise – A high power frequency power wave caused by radio frequency interference (RFI) or electromagnetic interference (EMI).
  7. Frequency variation – A loss of stability in the power supply’s normal frequency of 50 or 60 Hz.
  8. Switching transient – Instantaneous under-voltage in a matter of nanoseconds.
  9. Harmonic distortion – The distortion of a normal power wave, often transmitted by unequal loads.

So how does each UPS system protect you against the anomalies? Take a look:Power Anomalies Chart

For any critical environment, the cost of downtime is paramount in deciding what level of protection a facility requires.

For many facilities, power quality can often go undetected and can impact the total life cycle cost of equipment substantially. For the lab indicated above, the line-interactive UPS systems were protecting against a power outage, but not protecting the sensitive equipment against other transients and anomalies, costing thousands in premature equipment failure.

In short, line-interactive UPS systems may be cheaper, but they won’t provide you the same level of protection as an online double conversion system. If you want your mission-critical equipment to survive any of the nine power anomalies we discussed, an online double conversion system is the best option for your facility.

For questions, or to discuss power quality issues in your facility, take advantage of our reduced cost facility assessment.

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  1. […] electrical utility is delivering power normally; or from the battery, if the wall socket is dead. Quality Power Solutions offered a brief explanation of the superiority of this double-conversion approach. Drawbacks […]

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