This is a very interesting and potentially dangerous situation. The fact that it works with the breaker off (no power) points to a specific type of issue. Let's break down the possibilities and what to check.

Understanding the Problem

The core problem is that the holding circuit (the path that keeps the coil energized after you release the start button) is failing when the starter is powered. The coil de-energizes when you release the start button, indicating the holding circuit is not working correctly.The fact that it works with the breaker off and a paperclip jammed into the button indicates that you have a faulty electrical situation. DO NOT leave a paperclip in the starter. It is an arc flash hazard.Why it Might Work with the Breaker Off (but switch on).

The fact that it works with the breaker off but the switch on (I am assuming this means the control transformer is energized) points to a back-feed problem or some other unintended voltage potential problem on the control circuit. Here are the most likely scenarios:1. Back-Feed/Short Through the Motor

This is the most concerning. You could have a short within the motor winding that is feeding back voltage through the overload relay or even through ground. When the breaker is off, the motor is isolated and this back-feed disappears.

Action



Megger the motor

Use a megohmmeter to test the insulation resistance of the motor windings to ground. This is the MOST important step. Low insulation resistance indicates a short.

Check motor connections

Carefully inspect all motor connections for loose wires, burned insulation, or contamination.

Inspect the Motor

Visually examine the motor for signs of overheating, burned windings, or damage.2.

Ground Fault/Leakage Current in Control Circuit

You could have a ground fault within the control wiring that creates a path for leakage current. This current might be enough to interfere with the holding circuit. When the breaker is off, the main current is removed and the small leakage current is no longer enough to disrupt the starter.

Action



Isolate Control Circuit Sections

Disconnect parts of the control circuit one at a time to see if you can isolate the fault. Use a multimeter to check for voltage between the neutral and ground, with the breaker on.

Inspect Control Wiring

Carefully inspect all control wiring for damage, pinched wires, or loose connections.

Test Control Transformer

Check the output voltage of the control transformer to ensure it is within the specified range. Look for signs of shorting to ground in the transformer.3.

Voltage Drop/Improper Wiring

Although less likely since you've replaced components, a poor connection or undersized wiring in the control circuit could cause a voltage drop when the motor is running. When the motor is off (breaker off), the voltage might be sufficient to hold the starter.

Action



Measure Voltage at Coil

Measure the voltage directly at the starter coil while the motor is running. It should be within the coil's rated voltage range.

Check Wire Sizes

Verify that all wiring in the control circuit is of adequate size for the current draw of the coil.4.

Problem with Overload Relay

The overload relay could be malfunctioning in a way that only affects the holding circuit when the main power is applied.

Action



Bypass the Overload Relay (Temporarily and with Caution)

As a test ONLY, carefully bypass the overload relay contacts. If the starter now works correctly, the overload relay is likely the problem.

DO NOT operate the conveyor like this for any extended period; the overload relay is essential for motor protection.Troubleshooting Steps (in order of safety and probability)1. IMMEDIATELY REMOVE THE PAPERCLIP! This is a significant safety hazard.2. TURN OFF AND LOCK OUT/TAG OUT THE MAIN BREAKER. Safety first!3. Megger the Motor

As mentioned above, this is critical. Disconnect the motor leads before meggering.4.

Thorough Visual Inspection

Closely examine all wiring, connections, and components in both the power and control circuits. Look for: Burned or discolored wires/insulation Loose connections Corrosion Signs of arcing Water damage5.

Check Control Transformer

Verify the control transformer's primary and secondary voltages are correct. Also, check for a short between the transformer's windings and its case (ground).6.

Isolate Control Circuit

Systematically disconnect sections of the control circuit (one at a time) to see if you can isolate the problem area.7.

Test the Overload Relay

As a temporary test, carefully bypass the overload relay contacts. If the starter now holds, the overload relay is likely the cause. Do NOT run the conveyor for any length of time with the overload relay bypassed. Replace the overload relay immediately if it is faulty.8.

Voltage Drop Measurement

Measure the voltage at the starter coil while the motor should be running (if you could keep the start button held down). Compare this voltage to the coil's rated voltage.9.

Wiring Check

Double-check all wiring connections, ensuring they are tight and properly made. Verify that the wire sizes are adequate for the current draw of the coil.

Important Safety Considerations



Lockout/Tagout

Always follow proper lockout/tagout procedures before working on any electrical equipment.

Qualified Personnel

If you are not a qualified electrician, do not attempt to diagnose or repair this problem yourself. Call a professional.

Arc Flash Hazard

Working on energized electrical equipment poses a significant arc flash hazard. Wear appropriate personal protective equipment (PPE) if you must work on energized circuits.

Motor Protection

Do not operate the conveyor without a properly functioning overload relay. This is critical for preventing motor damage due to overcurrent conditions.

Conclusion:

The fact that the starter works with the breaker off but the control power (presumably) on strongly suggests a back-feed problem through the motor, a ground fault in the control circuit, or a subtle issue with the overload relay. Meggering the motor and carefully inspecting the wiring are the top priorities. This is a potentially dangerous situation, so prioritize safety and consider calling a qualified electrician. Don't use that paperclip! Flag for review