Should I use a constant voltage power conditioner instead of a UPS?
The question involves two different technologies used for differing reasons. 95% of all power quality problems are caused by transient noise, voltage surges, harmonics or frequently changing voltage conditions. Ferroresonant power conditioners provide the solutions for almost all of these power quality problems.
The primary function of any Uninterruptible Power Supply (UPS) is to provide an alternative voltage source (batteries) to a critical load for some period of time should a complete power failure occur.
What loads should not be powered by a UPS?
Loads that are highly inductive may cause a UPS to malfunction. Examples of equipment that should not be powered by a UPS include:
• Air conditioners
• Space heaters
• Vacuum cleaners
• Buffing machines
• Laser printers
• Transformers (step up/step down)
The majority of loads that require UPS protection are electronic-type loads. For example; process control, automation equipment, computer, and telecommunication. A UPS is also recommended to support microprocessor-based technology-type loads.
In addition, CVS and MCR power conditioner products are not recommended for use on the input and or output side of the UPS.
Why should only an on-line UPS be used with a standby generator?
An on-line UPS accepts input power with relatively wide variations in voltage and frequency, a common occurrence in power produced by standby generators. The true on-line (double conversion) technology provided by an on-line UPS handles these variations by converting the input power from AC to DC and then converting DC to AC output power. Generators should be equipped with an electronic governor to minimize frequency variations. Always check the frequency range of the generator output as the use of a mechanical governor does allow for large changes in frequency to reach the load. A wide frequency swing may cause the UPS to switch to the battery more frequently.
An off-line or line-interactive UPS is not recommended for use with a standby generator. An off-line UPS passes utility power straight through to the load. When a variation is detected, it can protect the load from the frequency variations of the standby generator by transferring to battery power. Occasionally, the input frequency will match the specifications of the off-line UPS and it will transfer back from battery. These occurrences are infrequent and short-lived, but the battery may not have sufficient time to recharge. It will support the load only until it is completely depleted and then shut down the load.
A line-interactive UPS faces the same issue as the off-line UPS. The power conditioning (tap switching) functions of the line-interactive units focus on correcting voltage variations and have no effect on frequency variations. The line- interactive unit reacts to out-of-spec frequencies similar to the off-line UPS.
The same input frequency variations that would cause an off-line or a line-interactive UPS to transfer to battery are of little concern or have no effect on the on-line UPS. On-line UPS's compensate for generator frequency variations while prolonging battery life.