Troubleshooting of Rockwell AutoMax DPS

Note: The non-volatile flash memory of the UDC module stores the PMI operating system. After replacement, PMI will request the operating system from UDC. As long as the UDC operating system exists and the parameters are correct, PMI will automatically download and run it.

Troubleshooting of Fiber Optic Link Malfunctions

The fiber optic link is the only communication channel between UDC and PMI, and its reliability directly determines system stability.

3.1 Typical faults

Link completely interrupted: PMI cannot start, UDC panel COMM LED is red or off.

High bit error rate: The drive occasionally reports "communication failure" and speed fluctuations.

Insufficient optical power: The received power measured by the optical power meter is close to the sensitivity limit of the receiver.

3.2 Diagnostic Tools and Procedures

Required tools: optical power meter (compatible with 650nm or 850nm wavelengths), fiber cleaning pen, spare fiber jumper.

Steps:

Disconnect the transmitting fiber at the UDC end, connect it to an optical power meter, and measure the transmitted optical power. The normal value should be ≥ the nominal value (usually -15dBm to -5dBm).

If the transmission power is normal, measure the received optical power at the PMI end. The allowed link loss should meet the optical power budget (transmit power receive sensitivity margin ≥ 0). The typical receiving sensitivity is -25dBm to -30dBm.

If the loss is too large (such as>10dB), check:

Is the bending radius of the optical fiber too small (should not be less than 10 times the outer diameter of the cable).

Whether the connector is contaminated (clean the ceramic plug with anhydrous alcohol and lint free cotton swabs).

Whether the fiber optic cable is stretched excessively (maximum allowable tension is specified in the cable specification).

Use a fiber optic fault locator or OTDR to locate breakpoints or macro bends.

3.3 Fiber replacement guide

When the fiber optic cable is damaged and needs to be replaced, it must use multimode fiber optic cables that meet Rockwell specifications (50/125 μ m or 62.5/125 μ m) and have a length not exceeding 750 meters. When making homemade optical fibers on site, attention should be paid to:

Use specialized fiber optic cutting knives and crimping tools.

Correctly install ST or SMA type connectors (recommended types in the manual).

Test insertion loss ≤ 0.5dB/connector.

PMI rack and module troubleshooting

PMI racks come in two types: 4-slot and 8-slot, depending on the type of drive. Taking the SA3000 high-power drive as an example.

4.1 Power module malfunction

The PMI power module provides 115VAC input and outputs DC voltages such as+5V and ± 15V to the backplane. Fault manifestation: All LEDs of the entire PMI rack are turned off.

Troubleshooting steps:

Measure the input terminal voltage (should be 115VAC ± 10%).

Check the LED on the power module panel: If the input is normal but there is no output, replace the power module.

Check if there is a short circuit on the backplane (unplug all modules and insert them one by one for testing).

4.2 PMI processor module failure

The PMI processor runs the inner loop algorithm and the panel has 5 status LEDs. Common faults:

LED 'RUN' not lit: processor is not running. Attempt to re download the PMI operating system through UDC.

LED "COMM" flashing: synchronization with UDC lost. Check the driver enable bits in the fiber optic link and UDC tasks.

LED "FLT" constantly on: hardware failure or internal self-test failure. The module needs to be replaced.

Note: The PMI processor module comes with two rail ports (Rail A/B) for connecting AutoMate digital/analog rails. If there is a communication failure in the rail, check if the rail cable is short circuited or if the terminal resistance is correct.

4.3 Rotary/Drive I/O Module Failure

This module provides a rotary feedback interface, analog input, and driver I/O. common problem:

Rotary feedback loss: Abnormal motor speed feedback. Measure the sine/cosine signal with an oscilloscope and check the shielding grounding.

Drive I/O point unresponsive: Check external wiring and module internal configuration (through variable mapping).

The rotary to digital converter of this module can automatically tune the cable length (up to 150 meters). If replacing the rotary cable, the "self-tuning" command should be sent through the UDC task.

4.4 AC power technology module malfunction

This module generates PWM trigger pulses and is connected to the power module through a parallel interface module (PIM) or directly. Fault manifestation:

PMI unable to output: The "EN" LED on the module panel is not lit. Check the enable conditions from the PMI processor.

Trigger pulse missing: Use an oscilloscope to measure the pulse at the module output. If the output is normal, the problem lies in the subsequent gate drive interface or power module.

4.5 Gate driver interface (GDI) module malfunction

In high-power driving, each power unit corresponds to a GDI module, which is connected to the IGBT gate driver through optical fibers. Fault phenomenon:

GDI module panel LED "PWR" is not lit: check the power supply of the backplane.