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A third-brush dynamo was a type of
Third Brush Generators
- Yesterday's Tractors website Electrical generators Automotive charging circuits Automotive electrics {{electric-power-stub
A third-brush dynamo was a type of dynamo
"Dynamo Electric Machine" (end view, partly section, )
A dynamo is an electrical generator that creates direct current using a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundati ...
, an electrical generator
In electricity generation, a generator is a device that converts motive power (mechanical energy) or fuel-based power ( chemical energy) into electric power for use in an external circuit. Sources of mechanical energy include steam turbines, g ...
, formerly used for battery
Battery most often refers to:
* Electric battery, a device that provides electrical power
* Battery (crime), a crime involving unlawful physical contact
Battery may also refer to:
Energy source
*Automotive battery, a device to provide power t ...
charging on motor vehicles. It was superseded, first by a two-brush dynamo equipped with an external voltage regulator
A voltage regulator is a system designed to automatically maintain a constant voltage. A voltage regulator may use a simple feed-forward design or may include negative feedback. It may use an electromechanical mechanism, or electronic components ...
, and later by an alternator
An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature.Gor ...
.
Construction
As the name implies, the machine had threebrushes
A brush is a common tool with bristles, wire or other filaments. It generally consists of a handle or block to which filaments are affixed in either a parallel or perpendicular orientation, depending on the way the brush is to be gripped durin ...
in contact with the commutator. One was earthed to the frame of the vehicle and another was connected (through a reverse-current cut-out) to the live terminal of the vehicle's battery. The third was connected to the field winding
A field coil is an electromagnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which a current flows.
In a rotating ...
of the dynamo. The other end of the field winding was connected to a switch which could be adjusted (by inserting or removing resistance) to give "low" or "high" charge. This switch was sometimes combined with the vehicle's light switch so that switching on the headlights simultaneously put the dynamo in high charge mode.
Disadvantages
The third-brush dynamo had the advantage of simplicity but, by modern standards, it gave poor voltage regulation. This led to short battery life as a result of over-charging or under-charging.See also
*Amplidyne
An amplidyne is an obsolete electromechanical amplifier invented prior to World War II by Ernst Alexanderson. It consists of an electric motor driving a DC generator. The signal to be amplified is applied to the generator's field winding, and ...
* Metadyne A metadyne is a direct current electrical machine with two pairs of brushes. It can be used as an amplifier or rotary transformer. It is similar to a third brush dynamo but has additional regulator or "variator" windings. It is also similar to an ...
References
Third Brush Generators
- Yesterday's Tractors website Electrical generators Automotive charging circuits Automotive electrics {{electric-power-stub