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Brushless DC motors can be given 3 - phase supply but due to basic considerations of many factors, DC motors are given single phase and AC motors can be both phases. The consideration for single phase to a DC motors are:-
Electrical Efficiency
Single-phase motors could be considered more electrically efficient because the circuits are less complex; fewer electrical steps must be taken to achieve a desired output.
Cost Efficiency
Single-phase motors are considered more cost efficient in a manufacturing environment because of their relatively low cost of implementation. Single-phase motors can be operated using a standard 120 volt wall outlet.
Control Efficiency
Three-phase motors are more efficient for use as a variable speed motor. Single-phase motors are more efficient for a single-speed device such as a washing machine.
Synchronization Efficiency
Single-phase motors are more commonly used in synchronized devices such as clocks or manufacturing environments when more than one motor must be used. They are easier to synchronize with other motors because of their low variable speed use.