Service Home Wye-Delta Contactor Troubleshooting Guide - NGC - TG0165

Wye-Delta Contactor Troubleshooting Guide - NGC - TG0165

16.2 Wye - Delta Contactor - Troubleshooting Guide

Last updated: 10/15/2025

Wye - Delta Contactor - Troubleshooting Guide - NGC

TG0165

Revision A - 03/2026

Wye / Delta - Troubleshooting Videos

Components

  1.  Wye contactor.
  2. Delta contactor.
  3. 120 VAC Power cable.
  4. Wye/Delta Feedback cable (NGC machines only)

Electrical Safety

 DANGER: Working with the electrical services required for CNC machines is extremely hazardous and can result in serious injury or death.

Before connecting line wires to the CNC:

  • Turn off all power to the machine at the source.
  • Perform a Lockout-Tagout (LOTO) procedure to ensure the power remains off during service.
  • Verify that power has been disconnected by using an AC voltage detector on all incoming lines.

If you are uncertain about how to safely disconnect power or perform LOTO procedures:

  • Do not proceed.
  • Contact qualified personnel or obtain appropriate assistance before continuing.

Failure to follow these precautions may result in electrical shock, equipment damage, or fatal injury.

 Danger: Before beginning any work inside the control cabinet, verify that the High Voltage indicator light on the 320V Power Supply / Vector Drive has been off for a minimum of five (5) minutes. This waiting period ensures that residual voltage has dissipated and reduces the risk of electric shock.

Certain service procedures involve high-risk electrical components and may pose serious injury or fatality hazards. Technicians must not attempt any procedure unless they have a complete understanding of the steps involved and the associated risks.

If there is any uncertainty regarding a procedure, contact your Haas Factory Outlet (HFO) to arrange for a qualified service technician.

Symptom table

SYMPTOM POSSIBLE CAUSE CORRECTIVE ACTION
Alarm 2041 VECTOR DRIVE OR SPINDLE AMPLIFIER-OVERLOAD, and/or the spindle load pegs to 200% when any spindle speed is commanded. There is an open coil on one of the Wye-Delta contactors. Check the Wye-Delta connections for arching or burn marks. Make sure the connections are tight.
There is no voltage from the I/O PCB to the Wye contactor coil. Measure the resistance and the voltage.  Refer to Wye Contactor Voltage Inspection section.
The encoder belt is damaged, or the Non-Contact Encoder has a fault Inspect the encoder belt, encoder connections, encoder gaps and encoder alignment.
Alarm 123 SPINDLE DRIVE FAULT at any spindle speed, and Alarm 2040 VECTOR DRIVE OR SPINDLE AMPLIFIER-SHORT CIRCUIT. Faulty Wye-Delta contactor assembly. Check the Wye-Delta connections for arching or burn marks. Make sure the connections are tight.
Faulty vector drive. Inspect the vector drive and look for a shorted output.

Go to: Vector Drive - Troubleshooting Guide to troubleshoot the vector drive.
Alarm 4.9973 INVALID POWER CONTROL STATE DETECTED after software update. The WYE/DELTA feeback cables are not connected or not connected correctly. See the NGC-WYE-DELTA with Feedback Troubleshooting section below.
The WYE/DELTA patch is enabled and the WYE/DELTA contactors do not have a feeback cable.
Alarm 9973 or 4.9973 INVALID POWER CONTROL STATE DETECTED when the machine accelerates to maximum RPM. There is a problem with the incoming AC line power. Check the incoming AC line voltage.  Make sure you have all three phases from the top of the main circuit breaker to the main transformer.
The DELTA contactor is not engaging, or the WYE contactor is welded shut. See the NGC-WYE-DELTA with Feedback Troubleshooting section below.

Alarm 4.9973 INVALID POWER CONTROL STATE DETECTED

AND

The machine has an ABB or Eaton brand assembly.

 The config files are out of date. Load the updated config files. Reference the Configuration File - Download/Load - NGC procedure.
20008 Wye/Delta recovery triggered: S (SPINDLE) notification in the alarm history.
 The control detected a possible problem with the WYE/DELTA contactors.

This message appears in the alarm history because the control detected the WYE/DELTA contactor feedback states to be incorrect but not long enough to generate alarm 4.9973. 

  • Check all the WYE / DELTA terminal connections make sure they have a tight connection. 
  • Check the transformer taps to be in the correct location.
  • Find out if these messages occur during heavy cuts.

Do not replace any parts, if these messages continue to occur generate an error report and email it to Haas Service.
Alarm 4.116  S(SPINDLE) SPINDLE ORIENTATION FAULT. There is a loose connection on the WYE/DELTA buss connectors. Inspect the WYE/DELTA contactor buss connections make sure they are making all the terminal leads.
Spindle load pegs to 200% There is an open coil on one of the Wye-Delta contactors. Check the Wye-Delta connections for arching or burn marks. Make sure the connections are tight.
There is no voltage from the I/O PCB to the Wye contactor coil. Measure the resistance and the voltage.  Refer to Wye Contactor Voltage Inspection section.
The encoder belt is damaged, or the Non-Contact Encoder has a fault Inspect the encoder belt, encoder connections, encoder gaps and encoder alignment.

NGC-WYE-DELTA with Feedback Troubleshooting

New versions of the NGC-WYE-DELTA assemblies come with a feedback cable. This feedback cable allows the control to detect the current state of the WYE-DELTA contactors. If the control detects an invalid contactor state (i.e. both contactors engaged, or not engaged when commanded) the control will generate an alarm.

For alarm 9973 or 4.9973 INVALID POWER CONTROL STATE DETECTED check the following:

  1. Search the NGC software release notes on the Haas Portal for any updates regarding alarms 9973 or 4.9973.
  2. Determine if machine is equipped with the WYE-DELTA with feedback. Look at the NGC I/O PCB P63 and P64 connectors you should have cables going to these locations .

     Note: Machines built after 8/2017 will have the new version of contactors installed (no patch is required). If a WYE-DELTA contactor assembly (with feedback cables) was field installed, a software upgrade, I/O PCB firmware upgrade, and a patch is required to activate this feature. Refer to the Wye-Delta Contactor - Replacement procedure for more details.

  3. Make sure the contactor is switching correctly and the correct feedback is being detected.
    • Go to Diagnostics > I/O tab.
    • Type in keyword "Main" and press [F1] to search.
    • Select 154, 158 (INPUTS), 56, 57 (OUTPUTS) and press the [ALTER] button to filter the WYE/DELTA inputs and outputs.
    • Use the table below to determine if the contactor feedback is correct.

 Important: If the contactor logic state is not correct check the wiring going to each contactor, also check that is connected correctly at the I/O PCB (P63 DELTA, P64 WYE) (see drawing of the feedback cable below). If the wiring is correct make sure the contactors are not mechanically stuck.

NGC WYE-DELTA Feedback Logic Table

Contactor State Diagnostic Input Value Diagnostic Output Value

WYE contactor = ENABLED

DELTA contactor = DISABLED

 (154) Main_Spindle_WYE_Input 0 (57) Main_Spindle_WYE 1
(158) Main_Spindle_Delta_Input 1 (56) Main_Spindle_Delta 0

WYE contactor = DISABLED

DELTA contactor = ENABLED

 (154) Main_Spindle_WYE_Input 1 (57) Main_Spindle_WYE 0
(158) Main_Spindle_Delta_Input 0 (56) Main_Spindle_Delta 1

Wye-Delta Assembly Inspection

Corrective Action:

Inspect the Wye-Delta assembly. Make sure that all connections are tight, and that there are no signs of arching or burn marks on the contactors, burnt marks on the jumper bus-bar or contacts.

With the machine OFF, measure the resistance across the coil between connectors A1 and A2. The resistance should read 10-100 Ohms. If the reading is open (OL) or less than 5 ohms, then the coil is defective.

Note: If the resistance measured is less than 5 ohms, then the short at the coil may have caused damage to the I/O PCB. Inspect the I/O PCB by following the I/O PCB - Troubleshooting Guide - NGC.

Power-up the machine and make sure that only the Wye contactor is energized when no spindle speed is commanded. If both contactors are closed at the same time, one of the contactors may be stuck (welded shut). The vector drive sees this condition as a short.

Wye Contactor Voltage Inspection

Corrective Action:

  1. Power up the machine and wait until the machine finishes booting up.
  2. Measure the voltage across the coil between the A1 and A2 connectors of the Wye contactor. It should read 120 VAC.
    • If the voltage is correct, but the contactor does not engage, the contactor may have a mechanical issue.
    • If there is no voltage present, the problem may be caused by the I/O PCB, or the wiring from the Wye/Delta to the I/o PCB
    •  Go to:

Delta Contactor Voltage Inspection

Corrective Action:

  1. Power-up the machine and enter a program in MDI that commands the spindle to spin at 2000 rpm. Slowly increase the spindle speed while observing the diagnostics page.
  2. Output (56) Main_Spindle_Delta.  At the moment this bit changes from 0 to 1, the Delta contactor is energized.
  3. Measure the voltage across the Delta contactor’s coil between the A1 and A2 connectors.
    • If the voltage is correct, but the contactor does not engage, the contactor may have a mechanical issue.
    • If there is no voltage present, the problem may be caused by the I/O PCB, or the wiring from the Wye/Delta to the I/o PCB
    • Go To:

Electrical Diagrams

Vector Drive - Wye-Delta System - Interconnect Diagram

Vector Drive - Wye-Delta System with Contactor Feedback Interconnect Diagram - Reference Only

Servo Amplifier - Wye-Delta System - Interconnect Diagram