GE DC Drives (BCH series) upgrade and replacement of old DC drives

Step 1: On site evaluation and data collection

Record the existing motor nameplate (rated armature voltage/current, excitation voltage/current, speed, insulation level).

Draw power circuit diagram: incoming circuit breaker, contactor, reactor, thyristor bridge (model, quantity, parallel connection), DC motor armature/excitation.

Draw a control interface diagram: What signal does the original control system send to the DC driver (speed given 0-10V, tension given 4-20mA, start stop dry contact)? ）.

Clear alarm and protection list: overcurrent, demagnetization, overtemperature, fast melting, etc.

Step 2: Design an upgrade plan

Determine whether to retain the existing thyristor power stack. If the thyristor itself is intact and its capacity meets the requirements, it shall be retained; Otherwise, replace with a new bridge of the same size.

Choose PIBe board: Copper output (short distance, cheap) or fiber output (long distance, anti-interference).

Determine the number of I/O points: which signals need to be connected to the new system (analog quantities: speed feedback, current feedback, actual tension value; digital quantities: closing permission, emergency stop, fault reset button, etc.).

Network integration: What protocol (Profinet, Ethernet/IP, Modbus TCP) does the upper PLC use, and select the corresponding communication card for PECe.

Step 3: Offline programming and simulation

Set up a P80i virtual environment in the office and write:

Current regulator (PI)

Speed regulator (including weak magnetic control)

Excitation control (constant current or weak magnetic)

Logic section (startup timing, fault chain)

Data exchange with upper level PLC (status words, control words, speed setpoint, etc.)

Simulate and verify that all limiting and protection logic is correct.

Step 4: On site disassembly and wiring

Disconnect the main power supply and control power supply of the old drive, and confirm that the capacitor is completely discharged.

Dismantle the old control board, trigger board, and I/O board, while retaining the thyristor stack, heat sink, fuses, and current transformers.

Install PECe controller (rail or panel installation), PIBe board installed near the power section. Use shielded cables to connect the CT secondary line and twisted pair cables to connect the encoder signal.

If triggered by fiber optic cables, lay out fiber bundles and pay attention to the minimum bending radius.

Step 5: Debugging and parameter tuning

Low voltage power on inspection: Disconnect the main circuit of the thyristor (or unplug the fast fuse) and only provide control power. Check PECe startup, PIBe power indicator light, and communication for normal operation.

Trigger test: Use the "manual trigger" function of P80i to pulse each thyristor one by one, and check the gate waveform with an oscilloscope.

Current loop closed-loop testing: Connect a dummy load (or temporarily block the motor, only measure the current loop response), adjust the current PI parameter through step setting, so that the overshoot is less than 10%, and the response time meets the original system specifications.

Speed loop closed-loop testing: Optimize the weak magnetic zone and below the base velocity to ensure stability and no oscillation.

Online and load testing: Coordinate with the upper level PLC to conduct acceleration and deceleration, forward and reverse rotation, and emergency stop tests; Assess performance based on actual processes such as tension and position.

Step 6: Documentation and Training

Deliver the following documents:

Hardware layout diagram and terminal wiring table

P80i project files (including comments)

Parameter Record Table

Common Alarm Handling Manual

On site operator HMI usage training

Common troubleshooting (after upgrade)

Even after careful debugging, abnormalities may still occur on site. The following are typical faults and troubleshooting methods.

6.1 System cannot start, PECe has no power indication

Possible reasons:

24VDC power supply not connected or fuse blown

PECe internal power module failure

exclude:

Measure the input voltage of PECe power supply (should be 22-28V DC).

Check if the external DC power output is normal.

If the voltage is normal but there is still no indication, replace the PECe body.

6.2 Motor does not rotate, HMI displays' Firing Fail '

Possible reasons:

The thyristor trigger line is disconnected or the sequence is incorrect

PIBe output channel is damaged

Thyristor gate open circuit

exclude:

Use the "pulse test" mode of P80i, trigger each thyristor one by one, and measure the gate cathode waveform with an oscilloscope (there should be a pulse group with amplitude>5V and width>30 μ s).

Check the power of the fiber optic transmitter/receiver using an optical power meter.

Check if the thyristor module is open circuit.

6.3 Actual current value fluctuates greatly or is incorrect

Possible reasons:

Current transformer (CT) secondary wire reversed or poorly shielded

CT input range configuration error on PIBe

There is a grounding fault on the motor side

exclude:

Measure the CT primary and secondary currents simultaneously using a clamp meter to verify if the transformation ratio matches.