This is a classic head-scratcher situation where you're caught in the middle and need to methodically troubleshoot. Here's a breakdown of thoughts, potential causes, and a plan of attack

Understanding the Problem:
Intermittent Tripping

The key here is that it's not constant. This points away from a simple overload (which would trip reliably) and more towards something that develops or changes over time.

"Power is good" and "Must be power" are unhelpful

These are common refrains when no one wants to take responsibility. You need data, not opinions.

Timing

The 3-4 day interval is significant. It suggests a heat buildup, degradation of insulation, or a slow change in a component's performance.

Recent Work

The rail replacement is important to consider, though potentially not directly related to the electrical issue. Could the vibration/movement involved in the rail work have disturbed something else?

Possible Causes (In order of likelihood)


Motor Issues



Winding Insulation Degradation

Over time, motor windings can deteriorate. Heat, vibration, and contamination cause the insulation to break down. This can lead to shorts between windings or to ground. This is the MOST LIKELY scenario given the motor's age, the intermittent tripping, and the high current draw of a motor.

Loose Connections Within the Motor

Vibration could have loosened internal connections.

Bearing Issues

Bad bearings put extra load on the motor and cause it to draw more current. You'd likely hear or feel this, but it can develop gradually.

Contamination

Check the motor for dirt, dust, oil, or other contaminants that could be affecting insulation.2.

Hydraulic System Problems



Hydraulic Pump Issues

If the hydraulic pump is becoming less efficient (due to wear), the motor will have to work harder and draw more current.

Hydraulic Oil Condition

Dirty or degraded oil can increase friction and load on the pump.

Valve Problems

Stuck or slow-acting valves in the hydraulic system can cause pressure spikes and overloads on the motor.3.

Electrical System Issues



Loose Connections

Even though the electrical contractor says the power is good, specifically request that they check every connection in the elevator circuit: Main breaker terminals, disconnect terminals, contactor terminals, motor terminals, etc. Look for signs of oxidation, burning, or looseness. Use a torque wrench to ensure proper tightening. Loose connections cause resistance, heat, and voltage drop, which can stress the motor.

Contactor Problems

The contactor (the relay that switches the motor on and off) could have worn contacts or a weak coil. Arcing or chattering can cause current spikes.

Ground Fault

A small ground fault might not trip the breaker immediately but could weaken the breaker or add heat, eventually leading to a trip.

Voltage Imbalance

A significant voltage imbalance on the 480V supply can cause the motor to draw excessive current. Have the electrical contractor measure the voltage on all three phases while the elevator is running under load.

Harmonics

Harmonics in the power system (caused by other equipment) can sometimes overload breakers. Less likely, but worth considering if other equipment has been recently added to the building.4.

Elevator Control System Issues



Faulty Control Logic

In rare cases, the elevator's control system could be malfunctioning and commanding the motor to run in a way that causes an overload.5.

The Breaker Itself (Again)



Defective Breaker

Although the breaker was replaced, there is still a small chance that you got another defective one. It's rare, but it happens.

Incorrect Breaker Type

Is the replacement breaker exactly the same type and rating as the original? It must be a motor-rated breaker.

Nuisance Tripping

If the breaker is old, it could be susceptible to nuisance tripping due to heat or vibration.

Troubleshooting Plan


Gather Data



Motor Nameplate Information

Get the motor's full nameplate details (HP, voltage, full load amps (FLA), service factor, etc.).

Breaker Details

Record the breaker's manufacturer, model number, and trip curve.

Fuse Details

Verify the disconnect fuses are correct amperage for the motor/application.

Operating Conditions

Document when the breaker trips: During up travel, down travel, starting, stopping, or at a specific floor.2.

Motor Testing (Essential)



Insulation Resistance Test (Megger Test)

This is critical. Use a megohmmeter to measure the insulation resistance between each motor winding and ground, and between windings. Low resistance readings indicate insulation breakdown. This must be done with the motor disconnected from the power supply. Record the temperature and humidity at the time of the test. A significant drop in insulation resistance over time is a clear indicator of a problem.

Motor Current Readings

Use a clamp-on ammeter to measure the current on each phase of the motor while the elevator is running under load (both up and down). Compare these readings to the motor's FLA rating. Also check for current imbalance between the phases.

Motor Voltage Readings

Measure the voltage on each phase at the motor terminals while the elevator is running under load. Look for voltage imbalance.

Motor Temperature

Use an infrared thermometer to check the motor's surface temperature. An unusually hot motor is a sign of problems.

Visual Inspection

Carefully inspect the motor for signs of overheating, damage, or contamination. Check the motor's cooling fan to make sure it's working properly.3.

Hydraulic System Check



Hydraulic Pressure

Have the elevator tech check the hydraulic pressure during operation.

Hydraulic Oil

Have the oil checked for contamination.

Listen for Noises

Listen for unusual noises from the pump or valves.4.

Electrical System Inspection (Again, Be Specific)



Tighten Connections

Have the electrical contractor methodically tighten every connection in the elevator circuit.

Contactor Inspection

Inspect the contactor contacts for signs of wear or arcing. Consider replacing the contactor if it's old or shows signs of damage.

Voltage Balance

Measure the voltage on each phase at the main panel, the disconnect, and the motor terminals, while the elevator is running under load.

Ground Fault Testing

Use a ground fault locator to check for small ground faults in the system.5.

Monitoring



Current Monitoring

Install a recording ammeter to monitor the motor current over several days. This can help you identify patterns or spikes in the current that might be causing the breaker to trip.

Temperature Monitoring

If you suspect overheating, use a temperature logger to monitor the motor temperature over time.

Communication is Key



Get Everyone On The Same Page

Schedule a meeting with the electrical contractor and the elevator technician to discuss the problem and coordinate troubleshooting efforts.

Document Everything

Keep detailed records of all tests, measurements, and repairs.

Don't Assume

Verify everything.

Important Considerations



Safety First

Working with electricity and elevators is dangerous. Only qualified personnel should perform testing and repairs.*

Code Compliance

Ensure that all work is performed in accordance with local electrical codes and elevator safety regulations.

In Summary:

The most likely culprit is a failing motor. The intermittent tripping, combined with the motor's age, points strongly in that direction. The insulation resistance test is the most important test to perform. If the motor checks out, then you need to systematically investigate the other potential causes, focusing on loose connections, hydraulic system problems, and the electrical supply. Good luck! Flag for review