RUPS
Rotary UPS
A UPS built around a rotating synchronous machine with kinetic storage, often coupled to a diesel engine for long backup.
SLD
Symbols · FESS
Flywheel energy storage
A rotating mass coupled to a motor-generator and converter that stores energy kinetically for short, high-power bursts.
In plain English
What does Flywheel energy storage mean?
Flywheel energy storage holds energy in a rotating mass, usually in a vacuum enclosure with magnetic or low-loss bearings. A motor-generator accelerates the rotor to charge and decelerates it to discharge, and a bidirectional converter links the variable-frequency machine to a DC bus or AC network.
A simple example
Single-line diagrams show a machine circle with a flywheel mass or disc symbol on the shaft and a converter block to the bus. Flywheels appear in rotary and some static UPS systems as a battery substitute, and in microgrids for frequency regulation and ride-through of short disturbances.
What the drawings help you do
Stored energy is usually small, from seconds to a few minutes at rated power, so the symbol does not imply long backup time. Standby losses, minimum speed and the energy actually usable between maximum and minimum speed must be read from the data sheet.
This particular reference
A rotating mass coupled to a motor-generator and converter that stores energy kinetically for short, high-power bursts. A flywheel stores kinetic energy for seconds to minutes; a battery stores chemical energy for much longer durations.
- DC
- Direct current: electricity flowing in one direction.
- AC
- Alternating current: electricity whose direction changes periodically.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: DC UPS, AC UPS and capacitor buffer modules · Battery energy storage and power conversion
SLD · FESS
What it represents
Flywheel energy storage holds energy in a rotating mass, usually in a vacuum enclosure with magnetic or low-loss bearings. A motor-generator accelerates the rotor to charge and decelerates it to discharge, and a bidirectional converter links the variable-frequency machine to a DC bus or AC network.
Single-line diagrams show a machine circle with a flywheel mass or disc symbol on the shaft and a converter block to the bus. Flywheels appear in rotary and some static UPS systems as a battery substitute, and in microgrids for frequency regulation and ride-through of short disturbances.
Stored energy is usually small, from seconds to a few minutes at rated power, so the symbol does not imply long backup time. Standby losses, minimum speed and the energy actually usable between maximum and minimum speed must be read from the data sheet.
How to read it
- Read discharge time at rated power rather than total stored energy.
- A converter is needed because machine frequency changes with speed.
Information to show or reference
- State power rating and ride-through time.
- Show converter and bus connection.
- Reference standby loss and containment data.
A distinction that matters
A flywheel stores kinetic energy for seconds to minutes; a battery stores chemical energy for much longer durations.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
DC UPS, AC UPS and capacitor buffer modules
Public uninterruptible power and buffer function context.
Battery energy storage and power conversion
Public energy storage system context.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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