The Roesel Motor GeneratorTM is designed to provide power conditioning and glitch protection in the most rugged of environments. This unique application of Written-Pole technology allows the Roesel Motor GeneratorTM to provide sensitive loads with a regulated source of power complete with electrical isolation from sags, surges, and transients, while eliminating the need for conventional UPS electronics and battery banks. The enhanced glitch protection capabilities made possible by the application of Written-Pole technology, allow the Roesel Motor GeneratorTM to isolate crucial loads from momentary power interruptions lasting in excess of 12 seconds, protecting these critical applications from more than 95% of all utility outages. An added feature of this enhanced glitch protection is the ability to use the Roesel Motor Generator TM as a transitional power supply capable of bridging the gap between the onset of a utility outage and the time required to bring an alternate standby power source on line.

Used by the US Government to protect radar sites across North America, the Roesel Motor GeneratorTM has proven its worth as a rugged, reliable platform for isolating critical equipment from all types of power quality problems.

Simple, Rugged Design

A revolutionary AC permanent magnet motor-generator together with an integrated low speed flywheel forms the basis of the Roesel Motor GeneratorTM. In addition to the application of Written-Pole technology, several innovative concepts applied to the design of the Roesel Motor GeneratorTM make it a truly revolutionary concept in power protection. The innovative external rotor design of the Roesel Motor GeneratorTM allows designers to incorporate the flywheel directly into the rotor of the motor generator eliminating the need for additional bearings and couplings, enhancing reliability and serviceability.

The use Written-Pole in the Roesel Motor GeneratorTM eliminates the need for high-power electronic devices to convert and regulate output frequency and voltage. This unique feature sets the Roesel Motor GeneratorTM apart from its competition, making it the only power protection device in the market that is able to maintain a constant frequency output while utilizing a rugged copper-in copper-out configuration for enhanced performance and improved reliability.

The low speed design increases bearing life and allows for the use of time-proven materials and maintenance practices further enhancing reliability and increasing serviceability, while eliminating the containment concerns related to high speed flywheel systems.

Environmentally Friendly & Battery Free

The Roesel Motor GeneratorTM stores energy in a low speed, high strength ductile iron flywheel, eliminating the requirement for environmentally sensitive chemical storage batteries that must be replaced at regular intervals to maintain satisfactory performance. This approach eliminates the ongoing problems of battery maintenance, monitoring, replacement and disposal, ensuring peak performance over a wide range of ambient temperatures in the most severe conditions.

Since the energy conversion process in the Roesel Motor GeneratorTM is mechanical rather then chemical, tolerance for temperature and environmental variations is dramatically enhanced, reducing the infrastructure costs for ventilation, filtering and air conditioning.

Superior Power Conditioning and Isolation

The innovative design of the Roesel Motor GeneratorTM uses Written-Pole technology to regulate the generator's output voltage and frequency at the source, eliminating the need for switching power electronic devices on the generator output. The patented design allows the Roesel Motor GeneratorTM to operate as a low impedance sinusoidal source of power capable of accommodating high concentrations of non-linear load while maintaining a high level of power quality and electrical isolation.

The unparalleled level of electrical isolation is a key benefit derived from the motor generator layout. Not only does the Roesel Motor GeneratorTM isolate sensitive equipment from the sags, surges, and transients common to the utility grid, it also prevents current harmonics generated by sensitive non-linear loads from migrating to other areas of the distribution system where problems may arise.

Reliable Glitch Protection

Numerous studies have shown that more than 95% of all utility interruptions are less than 10 seconds in duration. While the majority of these interruptions usually last for only a few cycles or seconds, they are the cause of significant reductions in plant productivity and profitability.

The Roesel Motor GeneratorTM uses a low speed flywheel to drive the generator during utility outages lasting in excess of 12 seconds, allowing the unit to maintain its rated load while isolating the output and maintaining operation of critical equipment. Upon restoration of utility power, the Roesel Motor Generator TM resumes operation and rapidly restores the flywheel to its rated speed preparing the unit for successive interruptions. The low speed design allows for significantly shorter recovery times than comparable high-speed designs, ensuring adequate coverage is maintained during frequent interruptions.

Transitional Power Source

The ability to ride through momentary power interruptions of significant duration also enables the Roesel Motor GeneratorTM to function as a bridge between the onset of a utility outage and the availability of a standby power source, ensuring continuous operation of vital process equipment. An added benefit of the enhanced coverage is a dramatic reduction in nuisance starts, a major source of wear and tear on standby power plants.


The low level of current harmonics generated by the Written-Pole drive motor, combined with its ability to restart immediately upon restoration of utility power without overloading the supply distribution, greatly simplifies the integration of standby power plants into the power protection system. The distribution-friendly design of the Roesel Motor GeneratorTM also allows for the use of simpler, lower cost transfer switches further reducing the complexity and cost of installations.