Okay, Jeff, let's break this down and troubleshoot logically. You've provided good information, and it points to a few key areas.

Summary of the Problem



Phase Loss Fault

The VFD reports a phase loss fault.

Voltage Present, No Current

You have voltage on all three phases, but no current on phase A.

Problem "Moves" with Wire Swap

Swapping the A phase wire with another phase causes the no-current condition to shift to the new location.

Motor Rewired

The motor was initially wired incorrectly (Wye instead of Delta) and has been corrected.

Three-Phase Supply Seems Okay

Another three-phase system (glycol chiller) in the same building is running with current on all three phases.

Diagnosis and Potential Causes

Based on your observations, here's a breakdown of potential issues and how to investigate them:1.

Wiring Problem Between the Breaker/Fuses and the VFD Input

This is the MOST LIKELY culprit based on the fact that the problem "moves" when you move the wire.

Inspect Wiring Thoroughly

Go back and

carefully examine the wiring from the breaker (or fuses) to the VFD input terminals. Look for: Loose connections at any terminal block, breaker, fuse holder, or wire nut. A loose connection can appear to have voltage but won't carry current. Damaged wiring (nicks, cuts, corrosion). Even a small nick can compromise the conductor and prevent current flow. Check inside the junction boxes that are between the breaker and the VFD. Pay special attention to crimped connections if used. A poor crimp can be a hidden point of failure. Torque Connections

Ensure all screw terminals are tightened to the proper torque specification. Under-tightening or over-tightening can both cause issues.2.

Motor Wiring Issue After Delta Rewiring

Even though you rewired the motor, double-check this.

Verify Delta Configuration

Absolutely confirm that the motor leads are correctly wired in the Delta configuration for your voltage. Use the motor's nameplate diagram and a reliable wiring guide. A slight mistake here can lead to unbalanced currents and VFD faults.3.

VFD Input Circuit Issue (Less Likely, But Possible)

While you replaced the VFD, there's still a small chance the replacement unit has a subtle problem.

Check Input Rectifiers (Advanced)

If you are comfortable with electrical testing, and only if the VFD is disconnected from power, you can use a multimeter in diode test mode to check the health of the input rectifiers inside the VFD. Look for differences in the forward voltage drop across the rectifiers on the input side. A shorted or open rectifier could cause the problem. This is getting into deeper troubleshooting, and you should only attempt this if you have the proper skills and safety training.4.

ABB ACS355 Parameter Configuration

It's worth a look (but less likely to be the problem now).

Parameter Check

Verify the VFD parameters related to motor nameplate data (voltage, current, frequency, etc.) and phase loss detection are set correctly. Some VFDs have adjustable sensitivity for phase loss detection. Consult the ABB ACS355 manual for the correct settings.

Motor ID Run

If the VFD supports it, perform a motor ID run (auto-tuning). This will allow the drive to learn the motor parameters and optimize its performance.5.

Utility Supply Imbalance (Unlikely, But Still Check)

You've indicated the glycol chiller is working. However, it's worthwhile to re-confirm the utility supply, especially under load.

Voltage Balance

Measure the line-to-line voltages simultaneously while the motor is trying to run. A significant voltage imbalance can cause problems.

High-Leg Implications

You have a 240/120 Delta High Leg system. Make sure you are aware of what phase the high leg is and connect accordingly. While it's unlikely to be causing THIS specific problem, it's something to keep in mind for future troubleshooting.

Neutral Connection (Less Likely)

While a Delta system doesn't inherently have a neutral, check that there are no improper neutral connections that could be interfering.

Troubleshooting Steps (In Order of Priority)


Focus on Wiring

Meticulously inspect every inch of wiring between the breaker/fuses and the VFD input terminals. Look for loose connections, damage, and poor crimps.

This is the most likely cause. Tighten all connections properly.2. Re-Verify Motor Wiring

Double-check the motor wiring diagram against the actual wiring in the junction box on the motor. Ensure it's definitely a Delta connection that matches the nameplate voltage.3.

Check the Load

Disconnect the motor from the system and run the motor without any load. If the current balances with no load, the problem may be in the conveyor system.4.

VFD Parameters

Review the VFD parameters related to motor data and phase loss detection.5.

Utility Voltage Balance Under Load

Measure the line-to-line voltages under load.6.

Advanced VFD Testing (if comfortable)

Check the input rectifiers with a multimeter (disconnected from power).

Important Notes



Safety First

Always disconnect power before working on electrical equipment. Verify the circuit is de-energized with a reliable voltage tester.

Qualified Electrician

If you're not comfortable with electrical troubleshooting, it's best to call a qualified electrician.

ABB ACS355 Manual

Keep the VFD manual handy. It contains valuable information about parameters, troubleshooting, and safety.

Let me know what you find as you work through these steps, and we can refine the diagnosis. Good luck! Flag for review