As shown in the illustration, simultaneously pulling in of both the forward and reverse contactors is preventing by both mechanical and electrical means. What statement is true concerning the two means of electrical interlocking used? See illustration EL-0139.
ā¢ Auxiliary contacts R and F on forward and reverse contactors in a reversing motor starter ā¢ Function of time-delay (time-closed) contacts like RCR and FCR in preventing immediate reversal ā¢ Difference between an instantaneous interlock and a time-delay interlock in motor control circuits
ā¢ Look at the control circuit path feeding the Forward coil and trace which normally closed contacts open immediately when the opposite direction is energized, and which only change state after a delay. ā¢ Ask yourself: which contacts are there purely to keep both contactors from being pulled in at the same time, and which are there to let the motor coast down before it is allowed to start in the opposite direction? ā¢ How does a time-closed contact behave differently from a standard auxiliary contact the moment its coil is energized?
ā¢ Verify which contacts are labeled simply R and F (auxiliary contacts) versus those labeled RCR and FCR with the time symbol beside them. ā¢ Confirm from the diagram which of these contacts are normally closed and open immediately upon coil energization. ā¢ Identify which contacts are associated with a timing function related to coast-down and therefore must introduce a deliberate delay before allowing the opposite direction to be energized.
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