Power Fault Detect Module - How it Works and Troubleshooting Guide (Classic Haas Control)

How It Works

The Power Fault Detect Module (PFDM) unit protects the machine in the event of power outage or brown out. It safely stops all machine motion when it detects a loss of power.

The PFDM unit is composed of a supply circuit with a capacitor bank [1] and a voltage monitor circuit [2].

  • Upon machine power-up, the PFDM takes 120 VAC from the power distribution board and rectifies (converts) the alternating current (AC) into direct current (DC).
  • This rectified DC voltage (165 VDC nominal) feeds the Low Voltage Power Supply (LVPS).
  • A red “Power ON” LED located on the PFDM indicates a normal operating condition.
  • Two non-replaceable fuses (one for each of the 120 VAC lines) protects the PFDM.
  • The voltage monitor circuit [2] monitors the incoming 120 VAC from the main transformer.

The PFDM voltage monitor circuit sends a low voltage (0-5 VDC) signal to the Maincon, this voltage will decrease in the same proportion as the incoming voltage. The Maincon or Mocon will monitor this voltage and produce alarm 971 INPUT LINE POWER FAULT if the voltage drops below a voltage set in the machine parameters.

The Maincon or Mocon uses the signal voltage from the PFDM and the value of Parameters 731 POWER FAULT MAX TIME and 730 POWER FAULT THRESHOLD, to determine if a power interuption exists.

Symptom Possible Cause Corrective Action Section
Alarm 937 INPUT LINE POWER FAULT. Poor incoming power quality. Check and monitor the AC power. 1
The connections at the circuit breaker, contactor and main transformer are loose. Check and tighten connections and terminals. 2
The coolant level sensor has a short circuit. Check the coolant level sensor. 3
The Machine does not turn on, and the red LED on the PFDM is off. Poor incoming power quality. Check and monitor the AC power. 1
Open fuses on the PFDM PCB. Check the fuses. 4

SECTION 1

Symptom: Alarm 937 INPUT LINE POWER FAULT. The machine does not turn on, and the red LED on the PFDM is turned off.

Possible Cause: Poor incoming power quality.

Corrective Action:

Check the integrity of the AC power to the machine:

  1. Monitor the AC power and ensure that all three phases are present and that the voltage is consistent.
  2. Check the 3-phase 120 VAC supply from the transformer at the Power Distribution card at connector P1.
    note: Probe Cables: White to Black, White to Red, and Red to Black.
  3. If the 3-phase 120VAC checks ok then proceed to section 2.

SECTION 2

Symptom: Alarm 937 INPUT LINE POWER FAULT.

Possible Cause: The connections at the circuit breaker, contactor and main transformer are loose.

Corrective Action: With the main breaker turned off.

Check and ensure that all connections at the main contactor [1], circuit breaker [2] and transformer [3] are tight and secure.

SECTION 3

Symptom: Alarm 937 INPUT LINE POWER FAULT.

Possible Cause: The coolant level sensor has a short circuit.

Corrective Action:

A coolant level sensor that has a short circuit can trigger this alarm. Disconnect the coolant level sensor, if the alarm goes away, go to diy.haascnc.com to troubleshoot the coolant level sensor.

SECTION 4

Symptom: Machine does not turn on, and the red LED on the PFDM is turned off.

Possible Cause: Open fuses on the PFDM PCB.

Corrective Action:

Make sure there are no open fuses [1] or damage to the components.

If the PFDM fuses are open, look for burnt components on the Low Voltage Power Supply (LVPS), also look for short circuit in the cables to the PFDM and the LVPS. If you find burnt components, replace the LVPS and the PFDM.

Be aware: Many service and repair procedures should be done only by authorized personnel. The service technicians at your Haas Factory Outlet (HFO) have the training, experience, and are certified to do these tasks safely and correctly. You should not do machine repair or service procedures unless you are qualified and knowledgeable about the processes.

Danger: Some service procedures can be dangerous or life-threatening. DO NOT attempt a procedure that you do not completely understand. Contact your Haas Factory Outlet (HFO) and schedule a service technician visit if you have any doubts about doing a procedure.

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