It makes a humming sound when the contactor is energized (relay contacts close), but it does not turn. fileġ0 Question 9 Examine this three-phase motor control circuit, where fuses protect against overcurrent and a three-pole relay (called a contactor) turns power on and off to the motor: Fuse Fuse Fuse Fuses Schematic diagram motor Motor Shaft Contactor After years of faithful service, one day this motor refuses to start. fileħ Question 7 Draw the necessary wire connections to build the circuit shown in this ladder diagram: Ladder diagram: L1 L2 Start Motor Illustration showing components: 7Ĩ L1 L2 Motor Relay (Dashed lines represent connections between relay terminals and socket screw lugs, hidden from sight) fileĩ Question 8 Identify at least one fault that would cause the motor to turn off immediately once the Start pushbutton switch was released, instead of latch in the run mode as it should: F1 To 3-phase power source T 1 L 1 L 2 F2 Start Stop motor For each of your proposed faults, explain why it will cause the described problem. Explain what this contact does, and why it might be called a seal-in contact. The normally-open contact shown in the low-voltage control circuit is commonly called a seal-in contact. In this particular case, I show a low-voltage control circuit and a 3-phase, higher voltage motor: F1 To 3-phase power source L 1 L 2 F2 Start Stop motor Explain the operation of this circuit, from the time the Start switch is actuated to the time the Stop switch is actuated. What happens when someone actuates the Run switch? What happens when they let go of the Run switch? fileĦ Question 6 A very common form of latch circuit is the simple start-stop relay circuit used for motor controls, whereby a pair of momentary-contact pushbutton switches control the operation of an electric motor.
What happens when someone actuates the Run switch? What happens when they let go of the Run switch? file Question 5 Interpret this AC motor control circuit diagram, explaining the meaning of each symbol: L 1 L 2 Run To 3-phase power source motor Also, explain the operation of this motor control circuit. It is your job to improvise a solution! file Question 4 Interpret this AC motor control circuit diagram, explaining the meaning of each symbol: L 1 L 2 Run To 3-phase power source motor Also, explain the operation of this motor control circuit.
This is a realistic scenario, where the only type of switch you have available is a SPDT, but the 4ĥ wiring diagram calls for something different. fileĤ Question 3 Draw the necessary wire connections to build the circuit shown in this ladder diagram: Ladder diagram: L1 L2 Toggle switch Motor Illustration showing components: L1 L2 Toggle switch (SPDT) Motor Relay (Dashed lines represent connections between relay terminals and socket screw lugs, hidden from sight) Yes, the Run switch shown in the diagram is a SPST, but the switch shown in the illustration is a SPDT. Compare these two equivalent diagrams: First, the ladder diagram: To 480 VAC L1 L2 120 VAC Toggle switch Motor Next, the schematic diagram: "Hot" To 480 VAC Relay () Mtr "Neutral" Based on your observations of these two diagrams, explain how electromechanical relays are represented differently between ladder and schematic diagrams. fileģ Question 2 Perhaps the most challenging aspect of interpreting ladder diagrams, for people more familiar with electronic schematic diagrams, is how electromechanical relays are represented. Re-draw this ladder diagram as a schematic diagram, translating all the symbols into those correct for schematic diagrams. While some symbols are identical (the toggle switch, for instance), other symbols are not (the solenoid coil, for instance). In this convention, the hot and neutral power conductors are drawn as vertical lines near the edges of the page, with all loads and switch contacts drawn between those lines like rungs on a ladder: To 480 VAC "Hot" Fuse "Neutral" 120 VAC Toggle switch Indicator light Limit switch Solenoid coil Temperature switch As you can see, the symbolism in ladder diagrams is not always the same as in electrical schematic diagrams. Resources and methods for learning about these subjects (list a few here, in preparation for your research): 1Ģ Question 1 Questions An alternative to the conventional schematic diagram in AC power control systems is the ladder diagram.
#Simutech troubleshooting control circuits answers for free#
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