The Difference between Online UPS and Standby UPS

Online UPS vs. Standby UPS

Similarities: Both online UPS and standby UPS provide power during outages, but their operation differs significantly.

Online UPS:

• Comprises a rectifier, battery, and inverter.
• Converts incoming AC to DC, charging the battery and supplying power to the inverter.
• Always active, delivering power seamlessly without switching between sources.
• Requires larger heat sinks due to consistent operation, generating more heat.
• Higher cost than standby UPS but offers zero transfer time.

Standby UPS:

• Directly supplies AC power to the load.
• During an outage, it switches to battery power, using a rectifier to charge the battery when AC is available.
• The inverter activates only when the main power fails.
• Typically has a transfer time of about 5 milliseconds.
• More efficient as the inverter and rectifier are not always active.

Key Differences

• Operation: Online UPS constantly delivers power from rectifier and inverter; standby UPS switches to battery during outages.
• Transfer Time: Zero for online UPS; about 5 ms for standby UPS.
• Inverter Status: Always on in online UPS; only activates during outages in standby UPS.
• Cost: Online UPS is more expensive but offers uninterrupted power.

Summary

Online UPS offers continuous power with zero transfer time but at a higher cost and heat generation. Standby UPS is more efficient and cost-effective but has a slight delay during power failures.