accelerated a large flywheel to store energy, which was consumed rapidly during a fusion experiment as the generator side acted as a brake on the flywheel. Similarly, the next generation U.S. Navy aircraft carrier Electromagnetic Aircraft Launch System (EMALS) will use a flywheel motor–generator rig to supply power instantaneously for aircraft launches at greater than the ship's installed generator capacity. Conversions Motor–generators may be used for various conversions including: Alternating current (AC) to direct current (DC) DC to AC DC at one voltage to DC at another voltage. (Also called a dynamotor, short for dynamo-motor) Creating or balancing a three-wire DC system. AC at one frequency to AC at another harmonically-related frequency AC at a fixed voltage to AC of a variable voltage AC single-phase to AC three-phase Variable AC voltage power supply Before solid state AC voltage regulation was available or cost effective, motor generator sets were used to provide a variable AC voltage. The DC voltage to the generators armature would be varied manually or electronically to control the output voltage. When used in this fashion, the MG set is equivalent to an isolated variable transformer. High-frequency machines An Alexanderson alternator is a motor-driven, high-frequency alternator which provides radio frequency power. In the early days of radio communication, the high frequency carrier wave had to be produced mechanically using an alternator with many poles driven at high speeds. Alexanderson alternators produced RF up to 600 kHz, with large units capable of 500 kW power output. While electromechanical converters were regularly used for long wave transmissions in the first three decades of the 20th century, electronic techniques were required at higher frequencies. The Alexanderson alternator was largely replaced by the vacuum tube oscillator in the 1920s. Motor–generators used to increase ride-through Motor–generators have even been used where the input and output currents are essentially the same. In this case, the mechanical inertia of the M–G set is used to filter out transients in the input power. The output's electric current can be very clean (noise free) and will be able to ride-through brief blackouts and switching transients at the input to the M–G set. This may enable, for example, the flawless cut-over from mains power to AC power provided by a diesel generator set. The motor–generator set may contain a large flywheel to improve its ride-through; however, consideration must be taken in this application as the motor–generator will require