To perform effective fault-finding, several key steps must be followed:
Identify the type of fault, whether it's related to logic, electrical issues, or defects.
Determine both the cause and the precise location of the fault.
Take appropriate actions to rectify and repair the root cause of the faulty circuit.
In addition, it's crucial for the person conducting the fault-finding procedure to have a good understanding of the appliance, apparatus, or machine's operation. This knowledge is essential for a smoother fault-finding process.
The following outlines a logic fault-finding procedure specifically demonstrated on a three-phase forward reverse panel:
Obtain the schematic diagram for the panel as it serves as a valuable reference during the fault-finding process.
Ensure proper polarity at the points of consumption.
Confirm that pole-switching devices, fuses, and circuit breakers are correctly connected in the phase conductor.
Verify that the phase terminals in fixed appliances and single-phase socket outlets are properly linked to the phase conductor.
Ensure that the center contact of each Edison-screw lamp holder is appropriately connected to the phase.
Maintain phase rotation and identification for three-phase systems on the supply side of all distribution boards.
Always ensure that the circuit is interrupted as intended when operating switching devices.
The identified fault in the operation is that the reverse contactor is not operating correctly in a motor forward/reverse control panel. Here are the steps to diagnose and potentially fix the issue:
Step 1: Switch on the main circuit breaker.
Step 2: Test the output side of the circuit breaker to ensure that power is present in all three phases. Check the voltage between phases and also between each phase and neutral. The voltage between phases should be between 380V and 400V.
Step 3: Switch on the control circuit breaker.
Step 4: Test the voltage on the output side of the control circuit breaker. The voltage should be between 230V and 250V.
Step 5: Push the forward push button. If the motor operates in the forward direction, it indicates that the forward circuit is fully functional.
Remember that the technician should not assume the faulty condition before starting the correct fault-finding procedure. It's essential to follow these steps systematically to identify and resolve the issue with the reverse contactor in the motor forward/reverse control panel.
Step 6: Push the reverse push button and observe the motor's response. If the reverse coil activates, the fault is likely on the main portion of the reverse circuit. If it does not activate, the fault may be in the control portion of the reverse circuit.
Step 7: If the reverse coil operates, test the voltage on the input side of the main contactor contacts. All three main contacts should have a voltage reading between 380V and 400V. If not, the fault likely lies between the power supply and the input of the main contactor contacts.
Step 8: Test the output side of the main contactor contacts. If the voltage readings are between 380V and 400V, then the contacts are intact. If not, the issue may be with the main contactor contacts.
Step 9: Test the connections between the contactor and the motor. If the connections are incorrect, the fault may be in the conductors between the motor and the reverse contactor contacts.
After these steps, you should have determined whether the fault is in the main circuit or the control circuit. If the fault is related to the control circuit (as per step b above), proceed to the following steps:
Step 10: Switch off the control circuit.
Step 11: Test the continuity of the supply to the input of the reverse start button. If there's an issue, replace the conductor from the supply to the reverse start push button.
Step 12: Test for continuity between the output of the reverse start push button and the reverse operating coil. If there's no continuity, replace the conductor to the reverse operating coil.
Step 13: Test the reverse operating coil. If it's faulty, replace the coil.
Step 14: Test the continuity of the neutral connection to the reverse operating coil. If it's not okay, replace the conductor.
This detailed procedure helps diagnose and repair faults in the reverse contactor circuit of the motor forward/reverse control panel, whether the issue is in the main or control circuit.
In summary, fault-finding involves a systematic approach, starting with the identification and location of the fault, followed by the necessary repairs or rectifications. Additionally, understanding the equipment's operation is essential. This logic fault-finding procedure has been exemplified within the context of a three-phase forward reverse panel, emphasizing the importance of having the relevant schematic diagram on hand for reference.
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