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361:, where utility power was supplied as alternating current. Trains were designed to work on direct current, since DC traction motors could be built with speed and torque characteristics suited to propulsion use, and could be controlled for variable speed. The AC induction motor was not as well suited to traction use when powered from a fixed frequency supply. Before the invention of
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The center-tapped winding forms the DC neutral wire. It needed to be driven by a mechanical power source, such as a steam engine, diesel engine, or electric motor. It could be considered a rotary converter used as a double current generator; the alternating current was used to balance the DC neutral wire.
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The advantage of the rotary converter over the discrete motor-generator set is that the rotary converter avoids converting all of the power flow into mechanical energy and then back into electrical energy; some of the electrical energy instead flows directly from input to output, allowing the rotary
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delivery systems that cropped up in the 1880s and early 1890s. These included single phase AC systems, poly-phase AC systems, low voltage incandescent lighting, high voltage arc lighting, and existing DC motors in factories and street cars. Most machinery and appliances at that time were operated by
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The self-balancing dynamo is of similar construction to the single- and two-phase rotary converter. It was commonly used to create a completely balanced three-wire 120/240-volt AC electrical supply. The AC extracted from the slip rings was fed into a transformer with a single center-tapped winding.
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substations using synchronous rotary converters operated until 1999. Compared to the rotary converter, the mercury arc and semiconductor rectifiers did not need daily maintenance, manual synchronizing for parallel operation, nor skilled personnel, and they provided clean DC power. This enabled the
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the AC input waveform with no magnetic components at all save those driving the switch. The rotary converter is somewhat more complex than this trivial case because it delivers near-DC rather than the pulsating DC that would result from just the reversing switch, but the analogy may be helpful in
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to be extracted from the rotor. This principle is taken advantage of by energizing the same rotor windings with AC power, which causes the machine to act as a synchronous AC motor. The rotation of the energized coils excites the stationary field windings producing part of the direct current. The
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AC replaced DC in most applications and eventually the need for local DC substations diminished along with the need for rotary converters. Many DC customers converted to AC power, and on-site solid-state DC rectifiers were used to power the remaining DC equipment from the AC supply.
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If the machine is brought up to synchronous speed by external means and if the direction of the current through the armature has the correct relationship to the field coils, then the coil will continue to rotate in synchronism with the alternating current as a
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tapped into its rotor windings at evenly spaced intervals. When a dynamo is spun the electric currents in its rotor windings alternate as it rotates in the magnetic field of the stationary field windings. This alternating current is rectified by means of a
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The stopgap of needing to use rotary converters was slowly overcome as older systems were retired or upgraded to match the newer AC universal system. AC to DC synchronous rotary converters were made obsolete by
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One way to envision what is happening in an AC-to-DC rotary converter is to imagine a rotary reversing switch that is being driven at a speed that is synchronous with the power line. Such a switch could
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DC power, which was provided at the user level by rotary converter substations for residential, commercial and industrial consumption. Rotary converters provided high current DC power for industrial
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The device can be reversed and DC applied to the field and commutator windings to spin the machine and produce AC power. When operated as a DC to AC machine it is referred to as an
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If the coil is rotated, two separate currents can be taken from the armature, one providing direct current and the other providing alternating current. Such a machine is called a
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converter to be much smaller and lighter than a motor-generator set of an equivalent power-handling capability. The advantages of a motor-generator set include adjustable
566:
Garud, Raghu; Kumaraswamy, Arun; Langlois, Richard (2009). Managing in the
Modular Age: Architectures, Networks, and Organizations. New York: John Wiley & Sons. p. 249
166:. This makes the rotary converter a hybrid dynamo and mechanical rectifier. When used in this way it is referred to as a synchronous rotary converter or simply a
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power rectification and inverting. They were commonly used to provide DC power for commercial, industrial and railway electrification from an AC power source.
575:
Hughes, Thomas Parke. Networks of Power: Electrification in
Western Society, 1880–1930. Baltimore, Maryland: Johns Hopkins University Press - 1993, pp=120–121
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Hughes, Thomas Parke. Networks of Power: Electrification in
Western Society, 1880–1930. Baltimore, Maryland: Johns Hopkins University Press - 1993, pp=120–121
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understanding how the rotary converter avoids transforming all of the energy from electrical to mechanical and back to electrical.
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In this first illustration of a single-phase to direct-current rotary converter, it may be used five different ways:
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new substations to be unmanned, only requiring periodic visits from a technician for inspection and maintenance.
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required direct current to start and stop their motors in perfect synchronization to prevent tearing the sheet.
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If the coil is rotated, alternating currents can be taken from the collector rings, and it is called an
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144:. The basic construction of the rotary converter consists of a DC generator (dynamo) with a set of
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if the coil is rotated, direct current can be taken from the commutator, and it is called a
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in the 1930s and later on by semiconductor rectifiers in the 1960s. Some of the original
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254:. A direct current can be taken from the commutator. When used this way, it is called a
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needed large amounts of on-site DC power for their main roll drive motors. Similarly,
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and an alternating current can be taken out of the collector rings. This is called an
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If a direct current is applied to the commutator, the coil will begin to rotate as a
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rotary converter, with the second phase connected at right angles to the first.
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rotary converter, with the phases separated by 120 degrees on the commutator.
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Rotary converters soon filled the need to use all the competing
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in 1888. A typical use for this type of AC/DC converter was for
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627:"Rotary Converter Power Technology: AC, DC, and Subway Power."
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New York's
Forgotten Substations: The Power Behind the Subway
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539:
Hawkins
Electrical Guide, 2nd Ed. 1917, p. 1461, fig. 2036
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Hawkins
Electrical Guide, 2nd Ed. 1917, p. 1460, fig. 2035
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Hawkins
Electrical Guide, 2nd Ed. 1917, p. 1459, fig. 2034
58:(DC), or DC to AC power, before the advent of chemical or
621:. New York: John Wiley & Sons. pp. 279–291.
372:, this conversion could only be accomplished using
88:rotary converter. (In actual use, the converter is
198:in the supply network; it also provided complete
136:, where the two machines share a single rotating
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548:Hawkins Electrical Guide, 2nd Ed. 1917, p. 1461
23:1909 500 kW Westinghouse rotary converter
162:, which is directly rectified into DC by the
132:The rotary converter can be thought of as a
301:. Unsourced material may be challenged and
158:other part is alternating current from the
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321:Learn how and when to remove this message
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353:The rotary converter was invented by
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299:adding citations to reliable sources
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615:"Converters, Synchronous or Rotary"
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120:Wiring schematic for a simplified
104:Wiring schematic for a simplified
74:Wiring schematic for a simplified
14:
670:
644:Electric power systems components
619:Handbook for Electrical Engineers
592:. Princeton Architectural Press.
467:Traction current converter plant
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346:Railroad Rotary Converter from
625:Greenberg, Bernard S. (1999).
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35:which acts as a mechanical
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462:Three-phase electric power
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240:inverted rotary converter
236:commutated electric motor
175:inverted rotary converter
229:double current generator
613:Slichter, W.I. (1917).
359:railway electrification
348:Illinois Railway Museum
66:Principles of operation
457:Rotary phase converter
452:Rotary converter plant
415:mercury arc rectifiers
376:or rotary converters.
363:mercury arc rectifiers
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263:Self-balancing dynamo
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442:Frequency converter
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388:processes such as
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82:single-phase
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398:paper mills
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142:field coils
140:and set of
122:three-phase
92:and uses a
79:Gramme ring
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659:Rectifiers
638:Categories
508:2022-11-15
474:References
370:rectifiers
215:alternator
164:commutator
160:slip rings
151:commutator
146:slip rings
90:drum-wound
654:Inverters
489:"History"
282:does not
106:two-phase
37:rectifier
649:AC power
430:See also
244:inverter
138:armature
54:(AC) to
41:inverter
338:History
303:removed
288:sources
183:rectify
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242:(see
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494:IEEE
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