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US 4,080,556 AGranted
Compound D.C. electrical motor with shunt field demagnetization protection
AssigneeCaterpillar Tractor Co.
InventorsFrank S. Buchwald, Ward L. Bivens
Life of this patent
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AssigneeCaterpillar Tractor Co.
InventorsFrank S. Buchwald, Ward L. Bivens
Estimating the term…
A DC electrical motor of the form having one field winding connected in series with the armature winding in addition to a shunt field winding connected in parallel with the armature winding is provided with a diode or the like in the shunt field winding circuit. This blocks reversed current flow in the shunt field winding which can otherwise occur during start-up due to an inductive interaction with the series field winding and armature circuit. The diode or the like enables faster magnetization of the stator poles by preventing creation of negative shunt field ampere turns due to the magnetic couple with the series field-armature circuit during the motor start period. Faster starting of the motor results, and adverse effects such as heating, brush deterioration, and commutation problems are reduced.
In a compound DC electrical motor having a rotatable armature with at least one armature winding and having a stator with at least one series field winding connected in series relationship with said armature winding, said stator also having at least one shunt field winding connected in parallel relationship with said armature winding and wherein inductive coupling is present between said series field winding and said shunt field winding, the improvement comprising at least one unidirectional current means for limiting current flow in said shunt field winding to flow in a single direction.
A compound direct current electrical motor comprising:
Dependencies are inferred from the claim text.