1. Definition and Core Working Mechanism

An Elevator UPS (Uninterruptible Power Supply) is a specialized emergency power system integrated with elevator control infrastructure, designed to provide seamless, stable alternating current (AC) during mains power interruptions or anomalies. Composed of four critical components—rectifier, battery pack, inverter, and static switch—it operates through three key phases :

• Normal Mains Supply: The rectifier converts AC to direct current (DC) to charge the battery pack while supplying stable DC to the inverter, which reconverts it to regulated AC for the elevator system.

• Mains Interruption: Within 0.3–10 milliseconds , the static switch activates battery power. The inverter transforms stored DC back to AC, maintaining continuous power for elevator operations.

• Mains Recovery: Automatically switches back to mains supply, resuming battery charging for subsequent emergencies.

This zero-interruption transition distinguishes it from conventional backup generators, which typically require 3–5 seconds to activate .

2. Compelling Necessity for Elevator UPS Installation

2.1 Safety Risk Mitigation

Sudden power outages cause elevators to halt mid-shaft, trapping passengers and creating psychological distress. A UPS enables the elevator to operate at a safe speed (0.1–0.2 m/s) to the nearest floor with leveling accuracy within 5mm, then automatically opens doors for evacuation . For car elevators, this prevents vehicle sway or damage from abrupt stops.

2.2 System Protection

Mains fluctuations (overvoltage, undervoltage, or harmonic distortion) account for 68% of elevator control system failures. The UPS filters and stabilizes incoming power, shielding sensitive components like frequency converters and microcontrollers from electrical damage .

2.3 Regulatory and Functional Compliance

In high-risk environments like hospitals and data centers, building codes mandate emergency power for elevators. A UPS ensures compliance while maintaining critical functions: emergency lighting, ventilation, and intercom systems remain operational to prevent secondary hazards like oxygen depletion .

3. Key Selection Criteria for Elevator UPS

3.1 Capacity and Runtime Configuration

• Capacity Calculation: Must accommodate both rated motor power (2.2kW–7.5kW for typical elevators) and 3–5x inrush current during startup. UPS capacity should be at least 1.5x the elevator’s maximum power. For a 7.5kW elevator, a minimum 11.25kVA UPS is required .

• Runtime Planning: Standard scenarios need 15–30 minutes (supporting 1–2 full leveling cycles), while hospitals demand 1+ hour runtime via extended battery banks . Lead-acid battery capacity follows: Battery Capacity (Ah) = Maximum Discharge Current ÷ C-rate (0.42 for 2-hour discharge) .

3.2 UPS Type Selection

Battery options include lead-acid (mature, economical, 3–5-year lifespan) and lithium-ion (high energy density, 5–8-year lifespan, space-saving) .

4. Typical Application Cases

4.1 High-Rise Commercial Building

A office tower in Shanghai deployed dual redundant UPS systems for 12 passenger elevators. During a 2025 grid failure, the UPS activated within 0.5ms, safely evacuating 217 passengers across 42 floors in 22 minutes .

4.2 Luxury Residential Car Elevator

A Beijing villa community integrated lithium-ion UPS with car elevators. The system maintained power for 40 minutes during a storm-induced outage, preventing damage to 7 high-end vehicles .

4.3 Hospital Emergency Elevator

A tertiary hospital in Guangzhou configured UPS with 2-hour runtime and generator backup. During a 3-hour blackout, it supported 3 emergency elevators transporting critical patients and medical equipment .

5. Maintenance and Longevity Assurance

5.1 Routine Maintenance Schedule

• Daily: Inspect indicator lights, fan operation, and error alarms.

• Monthly: Clean ventilation systems; test lead-acid battery voltage (maintain 12V±0.5V per cell).

• Annually: Conduct full-load discharge tests; replace aging batteries; calibrate protection parameters .

5.2 Common Fault Resolution

6. Conclusion

Elevator UPS serves as the "safety umbrella" for vertical transportation systems , integrating rapid response, precise control, and system protection. Its deployment is not merely a regulatory requirement but a critical investment in passenger safety and equipment longevity. Selection and maintenance should align with elevator type (passenger/car), building function, and local power conditions to maximize its emergency response capability.