Service Home Regen Vector Drive - Troubleshooting Guide - NGC - TG0117
Last updated: 06/01/2026

Regen Vector Drive - Troubleshooting Guide - NGC

Revision 1

TG0117

Revision E - 06/2026

Introduction

Download and fillout the Regen Vector Drive Inspection Report Checklist below before replacing any parts.

Regen Vector Drive Inspection Report Checklist

The Haas Regen Vector Drive (RVD) is the source of power for the spindle motor and the servo amplifiers. There is currently one size Haas RDV: 40HP, in the future this drive will replace the 20HP and 40HP VD.

  • The communication between the Maincon PCB and the RVD is now a digital instead of the previous analog version.  This allows for realtime communications and better fault reporting.
  • The RVD has all standard protections as the previous VD plus protection against temporary loss of line  during regeneration actions.
  • The Regen Drive consist of two sections:  Regeneative power supply and the Vector Drive section that consist of 6-transistos PWM modulated current controller.
  • The RVD firmware can be upgraded from the Haas Control the same way as the I/O PCB Firmware.

Regen Vector Drive Software Versions:

  • 100.20.000.1000 and later

Regen Vector Drive Software Versions Not Supported:

  • 100.21.000.1102
  • 100.21.000.1110
  • 100.21.000.1111
  • 100.21.000.1142

Required Firmware Version:

  • Regen VD FW V1.18

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 / Alarm:
Software Version 100.20.000.1111 or lower		 Symptom / Alarm:
Software version 100.20.000.1200 or higher		 Possible Causes Corrective Action
The DC BUSS gauge on the diagnostic page show incorrect readings. No change The software is outdated. Make sure the machine has 100.20.000.1011 or higher.  

Alarm 650 DC BUSS OVER VOLTAGE

 No change The bus voltage exceeded 420 VDC.  The Regen circuit failed to work during the motor decel. Measure the incoming voltage to the machine. See the Input AC Voltage section below.
The AC input voltage is too high.
Alarm 9955 VECTOR DRIVE OR DC POWER UNDER VOLTAGE No change The DC buss voltage is less than 100 VDC.  The AC input voltage is too low. Measure the incoming voltage to the machine. See the Input AC Voltage section below.
Alarm 647 REGEN LOAD SHORTED Alarm 9895 REGEN IGBT IPM SHORTED There is a short circuit on the AC input or Regen output See the Short Circuit Inspection section.
Alarm 993 SHORT CIRCUIT No change There is a short circuit on the motor output. See the Short Circuit Inspection section.
Alarm 200 HIGH VOLTAGE POWER SUPPLY OVER-TEMPERATURE Alarm 9896 REGEN OVERTEMP There is a problem with the vector drive cooling fan. Inspect the cooling fan.
Alarm 991 AMPLIFIER OVER TEMPERATURE No change There is a problem with the vector drive cooling fan. Inspect the cooling fan.
Alarm 991 AMPLIFIER OVER TEMPERATURE and Alarm 993 SHORT CIRCUIT No change There is a short circuit. See the Short Circuit Inspection section.
Alarm 648 DC BUS SHORTED No change There is a short circuit on the DC BUSS or the DC Buss Circuit Failed to charge. See the Short Circuit Inspection section.
Alarm 9931 UNDEFINED HIGH VOLTAGE POWER SUPPLY FAULT No change The AC input phases are not correct. Make sure the input AC voltage wires are going into the correct terminal.
Alarm 9911 AXIS AMPLIFIER CABLE DISCONNECTED Alarm 9911 AXIS AMPLIFIER CABLE DISCONNECTED
Alarm 9912 AMPLIFIER COMMUNICATION FAULT		 There is no communication with the Regen VD.  The RJ-45 cable is unplugged. Make sure the RJ-45 cable is connected between the Regen VD and Maincon PCB.

The drive is not powering up

and

Alarm 9931 UNDEFINED HIGH VOLTAGE POWER SUPPLY FAULT

 The Regen VD firmware is not up to date. Update the firmware to V1.18 or higher.
Alarm 646 ELECTRICAL SUPPLY ERROR Alarm 9894 VD REGEN VAC INPUT LOW The software is outdated. Make sure the machine has 100.20.000.1011 or higher.  
There is a AC input phase loss.  Or AC input voltage is less than 180 VAC (RMS) or higher than 276 VAC (RMS). Check the input AC voltage to the Regen VD.

The drive is not powering up

and

Alarm 646 ELECTRICAL SUPPLY ERROR

The drive is not powering up

and

Alarm 9894 VD REGEN VAC INPUT LOW

 The Regen VD firmware is not up to date. Update the firmware to V1.18 or higher. For instructions on how to update firmware refer to NGC - Firmware Update.
Alarm 646 ELECTRICAL SUPPLY ERROR is generated during acceleration and deceleration, especially with heavy loads or at high RPM. The Regen VD firmware is not up to date. Update the firmware to V1.18 or higher. For instructions on how to update firmware refer to NGC - Firmware Update.
There is a buzzing sound intermittently coming from the electrical cabinet. More often when the spindle is decelerating. There is no issue with the Regen VD. The buzzing sound coming from the electrical cabinet is normal behavior. If there are other alarms being generated then troubleshoot those alarms and ignore the buzzing sound.

Alarm 646 ELECTRICAL SUPPLY ERROR is generated while the machine is sitting idle. It can be intermittent.

AND/OR

There is also a clicking sound coming from the Regen VD while machine is idle.

 The incoming power configuration or the quality of the incoming power is causing the Regen VD to generate faults. Check what type of power is being used to run the machine. Check if the machine is using a phase converter, or an open leg delta configuration for incoming power.  Contact the local Haas Factory Outlet (HFO) for alternative power solutions. See the Alarm 646 section below.

Input AC Voltage

Corrective Action:

Measure the AC voltage between all three pair phases at the TB2 located on the main transformer.  The AC voltage (RMS) must be between 180 and 276 VAC (360 and 480 volts for high voltage option).

 The input voltage cables labeled 74, 75, and 76 must be moved to the terminal block triple which corresponds to the average voltage measured.

Firmware Update

Firmware upgrade for the Regen Vector Drive is only supported in Software 100.20.000.1000 or later.

It is the same process as upgrading the IO or Tool Changer boards but instead you would choose the “Vector Drive” option in the popup and choose the Vector Drive firmware.

Refer to I/O PCB Firmware Update procedure.

Alarm 646 - Electrical Supply Error

Alarm 646 - Electrical Supply Error is generated by the Regen VD reporting an AC fault. 

The condition of the machine when the alarm is generated is important to determining the root cause. Some details are provided below for the various conditions that are seen with the 646 alarm:

  • Alarm 646 is generated while the spindle is rapidly accelerating to high RPM.
  • Alarm 646 is generated while the machine is sitting at idle.

Below is some corrective action for these cases.

Alarm 646 when spindle is accelerating:

When the spindle is accelerating and the alarm is generated, there could be a buzzing sound coming from the electrical cabinet.

The buzzing sound is not related to the alarm being generated. The buzzing should be considered normal behavior particularly during spindle deceleration.

Check the firmware version of the vector drive by pressing Diagnostics and then navigating to the System tab [1].

Look for the current firmware version on the line for VD Version. For example the image shows that the Regen vector drive firmware is version V01.13 [2].

If the firmware is below V01.18 then update the firmware to the latest version. Refer to the NGC - Firmware Update procedure for more details.

Alarm 646 Intermittently while machine is sitting at idle:

Alarm can be generated while E-Stop is pressed or released while the spindle is sitting at idle. 

First, update the regen vector drive firmware to the latest version.

If the issue persists, check in the electrical cabinet for a clicking sound. This clicking sound would be coming from a relay inside the vector drive [1]. This is not normal behavior while the machine is sitting idle.

Note: To confirm the clicking is the relay you can also look for an indicator LED on the side of the vector drive [2]. It will turn on/off at the same time as the relay clicking. 

The clicking sound coming from the relay while the machine is idle is an indicator that the incoming power needs to be checked.

Check if the power supplying the machine is utilizing a phase converter or an open delta power configuration. These can cause imbalances in voltages and frequency that cause the regen vector drive to generate a fault.

Contact your local Haas Factory Outlet for alternative power solutions.

Refer to the decal shown to the left:

This machine is equipped with Regen Vector Drive. Use of Phase converters is prohibited as it will cause damage to both converter and the machine.

 Note: This decal is only on machines built in 2026 or later.

Short Circuit Inspection

Corrective Action:

Inspect the spindle motor cables. Make sure the spindle motor cables are not contaminated or pinched.

Inspect the vector drive. Disconnect all the vector drive terminals and do the following tests:

Set your meter to Ohms test mode.

  • Put the black lead on chassis with the red lead measure terminals 5 (A), 6 (B) and 7 (C).

If the meter does not show OPEN (O.L) the vector drive is damaged.

Set your meter to Ohms test mode.

  • Put the black lead on terminal 2 (+) with the red lead measure the motor output terminals 10 (A), 11 (B) and 12 (C).

The meter should show high resistance readings typically in the Kilo or Mega ohms or O.L.  If the meter reads very low resistance the Vector drive is damaged.

Note: If the meter shows O.L this indicates an open circuit and there is no short between the terminals.

Set your meter to Ohms test mode.

  • Put the black lead on terminal 4 (-) with the red lead measure the motor output terminals 10 (A), 11 (B) and 12 (C).

The meter should show high resistance readings typically in the Kilo or Mega ohms or O.L.  If the meter reads very low resistance the Vector Drive is damaged.

Note: If the meter shows O.L this indicates an open circuit and there is no short between the terminals.

Electrical Diagram