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Goals:
• Read and interpret diagrams using multiple push-button stations.
• Draw diagrams using multiple push-button stations.
• Connect multiple push-button stations.
The conventional three-wire, push-button control circuit may be extended by the addition of one or more push-button control stations. The motor may be started or stopped from a number of separate stations by connecting all start buttons in parallel and all stop buttons in series.
The operation of each station is the same as that of the single push-button control in the basic three-wire circuit covered in Unit 18.Note in ill. 1 that pressing any stop button de-energizes the coil. Pressing any start button energizes the coil.
When a motor must be started and stopped from more than one location, any number of start and stop buttons may be connected.
Another possible arrangement is to use only one start-stop station and several stop buttons at different locations to serve as emergency stops.
Multiple push-button stations are used to control conveyor motors on large shipping and receiving freight docks.
ill. 1 Three-wire control using a momentary contact, multiple push-button
station.
QUIZ:
1. Using the schematic diagram in ill. 2, determine the number of control wires needed to control the three-phase motor. Use the terminal and wire identification shown in the schematic as well as proper power circuit identification.