Power Fault Detect Module (PFDM) - Troubleshooting Guide - CHC

Introduction

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

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 937 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 Table

Symptom	Possible Cause	Corrective Action
Alarm 937 INPUT LINE POWER FAULT.	Poor incoming power quality.	Check and monitor the AC power.
	The connections at the circuit breaker, contactor and main transformer are loose.	Check and tighten connections and terminals.
	An analog sensor or cable has a short-circuit.	Refer to: Analog Sensor - Troubleshooting Guide
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.
	Open fuses on the PFDM PCB.	Check the fuses.
Multiple alarms at power on: probe, amplifier, vector drive, pallet changer, etc...	There is a problem with PFDM.	Disable the PFDM PCB, see section below.

Incoming Voltage

Corrective Action:

Check the integrity of the AC power to the machine:

Monitor the AC power and ensure that all three phases are present and that the voltage is consistent.
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.
If the 3-phase 120VAC checks ok then proceed to section 2.

Voltage Connections

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.

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.

Disable the PFDM PCB

Corrective Action:

Set parameters 730 PWR FAULT THRESHOLD and 731 PWR FAULT MAX TIME to 0.

Turn OFF the main circuit breaker and wait until the red high voltage LED is turned OFF.

Disconnect the power fault signal cable from the PFDM to the Maincon/ Mocon at P26.

Turn on the machine. If the alarms go away replace the PFDM PCB.