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Plural motor fan system with improved speed control










Image Number 6 for United States Patent #4988930.

A two motor assembly for driving two fan blades to move air through a heat exchanger comprising a first two speed DC motor comprising magnets for establishing a fixed magnetic field, an armature rotor rotatable to drive a first fan blade, a multiplicity of armature coil turns on the armature rotor, a commutator assembly on the armature rotor, and sets of brushes including a tap brush cooperating with the commutator assembly to alternatively operate the two speed DC motor (1) is a first speed mode wherein (A) a system voltage is applied and distributed across all of the multiplicity of armature coil turns to produce a net total back EMF and armature reaction interacting with the magnetic field to cause the armature rotor to rotate in the first speed mode and (B) a tap voltage intermediate the system voltage reduced across a predetermined number of armature coil turns less than all of the multiplicity of armature coil turns is provided through the tap brush and (2) a different second speed mode. Circuitry is provided for alternatively (1) applying the tap voltage across the armature coil of a second DC motor so as to operate the second DC motor in a first speed mode when said first two speed DC motor is operated in the first speed mode thereof and (2) applying the system voltage across the armature coil of the second DC motor so as to operate the second DC motor in a second speed mode when the first two speed DC motor is operated in the second speed mode.








 
 
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