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Flywheel UPS

The CAT Flywheel UPS provides our highest efficiency continuous power solution (>97% efficient). This technology uses a power dense integrated flywheel, which stores sufficient energy to ride through power disturbances such as dips or surges in voltage and/or current. The stored power is immediately available for delivery to a critical load during a power disturbance. This system provides ample ride-through time and allows for an orderly walk-in of the generator set to assume the load for the duration of the disturbance. The integrated flywheel design is modular, supporting easy expansion to meet future power quality/power protection requirements. The CAT Flywheel UPS delivers lower operating costs due to several factors, including lower maintenance and replacement costs, the space savings associated with a reduced footprint (75% smaller than a battery based UPS system) and a yearly energy efficiency improvement of 4%. With the Flywheel UPS, you also benefit from reduced upkeep and maintenance, field-proven mechanical energy storage that is predictable and fail-safe, nearly unlimited life with no fall-off in performance and a broad operating temperature range up to 104° F. Additionally, this technology is environmentally friendly, thereby posing no safety hazards to either your personnel or the environment.

Working of the CAT FLYWHEEL UPS

Flywheel Technology

Flywheel Technology
4.4” high; 25.5” diameter; 600 lbs
Each flywheel provides 250kW for ~28 seconds at 50% load


Flywheel process

Advantages of CAT Flywheel UPS


  • CAT Flywheel UPS uses an online active filtering design to provide exceptional performance with high efficiency
  • The online active filtering design passes the load current directly through the UPS
  • kVAR and Harmonic current are provided to the load from the Utility Convert
  • A small regulator current is managed between the input and utility convert to provide the active filtering of the input sine wave
  • A small charging current (about 1kW) is drawn from the input to maintain the flywheel charge


  • Single Flywheel
  • 480V @ 60HZ, 750KVA/675KW
  • 400V @ 50/60HZ, 625KVA/625KW
  • Parallel up to 8
  • 3.4m x 1m x 2m
  • 5375 kg


Maintenance Comparison
CAT Flywheel UPS Double Conversion/Battery UPS
When Required Monthly
– Clean the Flywheel housing – Battery inspection/clean*
– Clean the oil level site gauge – Torque battery terminals*
– Check the oil level – Clean internals
Every 3 Months Every 3 Months
– Clean/check Air Filter – Clean/check Air Filter
– Battery Test – Ohmic*
Every Year Every Year
– Change the Vacuum Pump Oil – Battery Test – Resistance*
Every 3-4 Years
– Flywheel Bearing Replacement
Every 5 Years Every 5 Years
– Replace Controller Battery – DC Capacitor Replacement
– Battery Replacement
Every 10 Years Every 10 Years
– DC Capacitor Replacement – AC Capacitor Replacement


Cooling Comparison
CAT Flywheel UPS Double Conversion/Battery UPS
Heat Rejection of 1200kVA UPS Heat Rejection of 1100kVA UPS
– 83,967 BTU/HR – 250,000 – 339,000 BTU/Hr**
– 24.6 kW – 74 – 99.35 kW**
UPS Temp Limits UPS Temp Limits
– 0-40°C (32°F – 104°F) – 0-40°C (32°F – 104°F)
Energy Storage Temp Limits Energy Storage Temp Limits
– 0-40°C (32°F – 104°F) – 25 °C (77 °F)*
– Life decreases 50% for every 8 °C to 10 °C increase*
– Batteries have less capacity at colder temperatures*



  • Voltage Range +10% / -15% (programmable)
  • Frequency 60 Hz +/- 10% max (programmable) +/- 3% (default)
  • Power Factor 0.99 at rated load and nominal voltage
  • Harmonic Current Distortion <2% at 100% linear load


  • Steady state Voltage regulation +/-1%
  • Voltage distortion <1% linear loads
  • Frequency 60Hz (mains synchronized)

– (normal operation +/- 0.2% free running)

Power Correction

Voltage is monitored at three locations within the UPS – Input, Bypass and Output

  • Bypass voltage is used to confirm voltage before transfer
  • Input voltage is used to determine disconnect
  • Output voltage is used for correction


Flywheel UPS Product Line

Flywheel UPS Product Line

Flywheel UPS Product Line