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

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

Introduction: The dilemma and necessity of upgrading old DC drives

In heavy industries such as metallurgy, papermaking, mining, lifting, plastics and rubber, a large number of DC drives have been running continuously for more than ten or even more than twenty years. These devices were once the heart of the production line, but over time, they are facing three fatal challenges:

Outdated platform and shortage of spare parts: The core boards (such as trigger boards and adjustment boards) have been discontinued by the original factory, and replacement parts are difficult to buy in the market. Maintenance can only rely on dismantling old machines or high imitation products, with extremely low reliability.

Specialized hardware and closed architecture: Old drivers use a large number of cables, custom connection boards, and application specific integrated circuits (ASICs). Once a non-standard component is damaged, the entire system may shut down for several weeks.

Difficulty in integrating with upper level control systems: Old drivers only support analog or dedicated protocols (such as GE's CIM and DCS link), which cannot integrate into modern open networks such as Ethernet/IP, Profinet, Modbus TCP, etc., resulting in data monitoring and automation upgrades being hindered.

In response to the above difficulties, the industry generally adopts two strategies:

Replacing the entire machine with an AC frequency converter: high cost, large engineering workload, need to replace the motor, and some high inertia loads (such as flying shears and coilers) still prefer DC drive.

Staged upgrade and renovation: retaining the existing power stack (thyristors, heat sinks, main circuit), only replacing the control part and trigger interface - this is the technical route that this article focuses on discussing.

This article will take GE Power Conversion's DC drive upgrade solution as an example to analyze in detail how to achieve non-destructive and phased replacement of old DC drive systems through open architecture, industrial computer controllers, and modern software platforms, significantly improving reliability and extending equipment life.

Overall upgrade strategy and advantages of open architecture

2.1 Core principles of upgrading and transformation

Successful DC driver upgrades should follow the following principles:

Maximize the retention of existing facilities such as power stacks, transformers, DC motors, and on-site cables for continued use.

Phased implementation: Upgrade a single key equipment (such as a coiler) first, validate it, and then promote it to avoid full line shutdown.

Open and scalable: The new control system must support multiple industrial Ethernet protocols and seamlessly integrate with PLC/DCS.

Simplify spare parts inventory: Use commercial off the shelf (COTS) components (such as industrial PCs, standard I/O modules) instead of customized boards.

2.2 Key Benefits of Open Architecture

The core of GE's solution lies in an open architecture, which has the following significant advantages compared to traditional closed DC drivers:

Characteristics: Traditional Closed Drive Open Architecture Upgrade Solution

Controller specific CPU board, discontinued standard industrial PC (PECe), Intel chip, can be independently replaced

Connection method: ribbon cable, customized harness without ribbon cable design, Ethernet, fiber optic, standard terminal

Network protocol proprietary protocols Modbus TCP, Profinet, EtherCAT, EGD, Profibus

I/O expansion fixed point or expensive expansion card third-party EtherCAT I/O, modular free combination

Software platform specific programmer, parameter obscure IEC 61131-3 functional block diagram, Windows environment, online simulation

After the original factory shutdown, the spare parts lifecycle is completely out of stock. Industrial PCs and standard I/O are available for long-term market supply

Key design highlights:

No wiring harness/dedicated wiring harness: Traditional drivers have multiple card boards connected by flat wiring harnesses, which can easily cause poor contact after vibration or oxidation. The GE solution completely eliminates these fault points through PECe controller+PIBe interface board+EtherCAT bus.

Retain the original power stack: Existing GE or third-party thyristor bridges, heat sinks, fuses, and reactors can continue to be used, with only the control part replaced, saving more than 60% of renovation costs.

Detailed explanation of core hardware components

The hardware of the upgraded system consists of four main parts: PECe controller, PIBe power interface board, EtherCAT field I/O, and human-machine interface.

3.1 PECe - The Brain of Drivers

PECe (Power Electronics Controller) is a reinforced industrial computer designed specifically for harsh electrical environments.

Key parameters:

Processor: Intel chip, 1.2~2.5 GHz, supports dual core/quad core

Operating system: Real time operating system VxWorks, ensuring deterministic response (μ s level)

Working temperature: 0~60 ° C, fanless design (maintenance free)

Ethernet interface: 5 10/100 Mbps ports for network control, debugging, and synchronization

Expansion slots: 2 or 4 PCI slots that can accommodate communication cards such as Profibus, Profinet, Reflective Memory, CANbus, Modbus, EGD, etc

Programming environment: Complies with IEC 61131-3 standard, supports Function Block Diagram (FBD), Ladder Diagram (LD), Structured Text (ST)

Engineering significance: When the controller fails, it can be directly replaced with an industrial PC of the same model, and the application program can be reinstalled to restore it without waiting for the original factory's dedicated spare parts.

3.2 PIBe - Bridge Connecting Controller and Power Section

PIBe (Power Interface Board) is a critical interface board that connects PECe with on-site power devices such as thyristors, transformers, encoders, etc. Provide:

24 copper cables or 32 optical fibers output to thyristor trigger circuit (capable of withstanding 60V, 10A)

8-channel digital input (such as emergency stop, closing feedback)

4-channel digital output (such as contactor control)

8 analog inputs (± 10V, 4-20mA, used for current/voltage feedback)

4-channel analog output (for external instruments or auxiliary adjustment)

2-channel current transformer input (directly connected to Hall effect sensor or CT)

1-channel encoder input (for speed feedback)

Advantages of fiber optic isolation: For high voltage and strong interference scenarios (such as large rolling mills), using fiber optic triggered thyristors can completely solve the problems of common mode voltage and ground current, greatly improving reliability.

3.3 On site I/O and EtherCAT Technology

The upgrade plan supports modular on-site I/O (such as GE RSTi series), connected to PECe through EtherCAT bus.

EtherCAT technology features:

Real time transmission, with a cycle time as low as 125 μ s

High synchronization accuracy (<1 μ s jitter)

Supports a large number of binary/analog channels, suitable for complex logic interlocking (such as crane brake, limit switch, temperature monitoring)

Practical application: In the control of the coiler, the tension meter signal, speed encoder, limit switch, cooling fan status, etc. can all be connected to PECe through EtherCAT I/O to avoid long-distance analog signal attenuation.

3.4 Human Machine Interface (HMI)

Replace the original pointer instrument, selector switch, and neon light. Configure a local touch screen that typically displays:

Main screen: Armature voltage, current, speed, excitation current, operating status, alarm overview

Alarm history: Record the last 100 faults (such as overcurrent, demagnetization, overspeed, thyristor trigger failure)

Parameter adjustment: PI parameters, acceleration and deceleration time, current limiting, etc. can be fine tuned online

Benefits: Reduce control cabinet openings, simplify operations, and provide intuitive fault location.

Software Platform: P80i Toolbox

4.1 Overview of P80i

P80i is a unified software suite for GE Power Conversion, covering the entire drive lifecycle: configuration, programming, debugging, monitoring, and fault diagnosis.

Operating environment: Windows (7/10/11), connected to PECe controller via Ethernet.

Compliant with IEC 61131-3: Supports Function Block Diagram (FBD), Ladder Diagram (LD), Sequential Function Diagram (SFC), and Structured Text (ST). This allows engineers familiar with PLC programming to quickly get started without the need to learn specialized driver parameter languages.

4.2 Main functions and advantages

Function Description

Real time monitoring of all variables (current, speed, trigger angle, temperature) through online monitoring, with graphical trend curves

Offline simulation simulates drive behavior on a PC without real hardware, verifies control logic, and shortens on-site debugging time

Modular programming can reuse functional block libraries (such as current loop, speed loop, tension control) to enhance standardization levels

Version control engineering projects can be saved as text/binary files for easy backup and comparison of differences

Multi user support allows multiple people to connect to the same controller simultaneously and monitor different tasks separately

Typical Debugging Scenario - Magnetic Field Closed Loop Test (PERTU):

When the motor is not closed or the load is not connected on site, the excitation circuit can be tested separately through P80i - set the excitation current setting, observe the actual current feedback, adjust the PI parameters, and confirm that the thyristor triggers normally. This greatly reduces the risk time during motor debugging.

4.3 Alarm and Diagnostic Examples

The P80i is equipped with rich diagnostic functions, and common alarms include:

Firing Fail ": Loss of thyristor trigger pulse (check fiber or PIBe output channel)

Overcurrent ": Current feedback exceeds the limit (check CT signal or current loop parameters)

Field Loss: Low excitation current (check excitation bridge or motor field winding)

Encoder Fault: Speed encoder signal loss (check wiring and encoder power supply)

All alarms are time stamped and can be exported for analysis.

Engineering implementation steps: from old drives to new systems

The following is a typical process for upgrading a 15-year-old DC speed regulator (such as GE DV300, DC2000, or third-party brands) to a PECe+PIBe solution.

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.

Check if the wiring is twisted pair shielded and if the shielding layer is grounded at one end.

Viewing the original AD value in P80i software, if there is significant noise displayed, it may be due to interference from the frequency converter.

6.4 Periodic speed oscillation of motor

Possible reasons:

The PI parameter ratio of the speed loop is too large or the integral is too small

Loose coupling of speed encoder or signal interference

exclude:

Temporarily halve the proportional gain of the speed loop and observe whether the oscillation weakens.

Check the installation of the encoder and the grounding of the shielding layer.

Plot the given speed, actual speed, and current simultaneously in the P80i trend window, and analyze whether the oscillation frequency is consistent with the mechanical resonance point.

6.5 Intermittent communication with upper PLC

Possible reasons:

Network cables are too long or of poor quality

IP address conflict

High network load leads to packet loss

exclude:

Check the length of the network cable (<100m) and use a professional tester to measure signal attenuation.

Put the driver and PLC into the same VLAN and broadcast them separately.

Check the packet loss rate on the Ethernet diagnostic page of PECe (should be<0.01%).

Service and Support: Ensuring Long Term Availability

Upgrading cannot be just a one-time project, long-term maintenance capability is equally important. GE provides the following services:

24/7 Global Support Center: Telephone or online remote diagnosis.

Visor Connect remote support system: Through the secure satellite/Internet link, experts can remotely view the screen of field engineers to guide troubleshooting.

Spare parts strategy: Key components such as PECe, PIBe, and power modules are stocked in regional warehouses and promised to be shipped within 48 hours.

Regular health check: Conduct on-site or remote check ups once a year, including parameter backup, waveform recording, and thermal imaging inspection of power devices.

Training: Provide beginner and advanced courses (including practical exercises) for maintenance engineers.

For extremely old systems that are completely irreparable (such as early analog SCR control), GE also provides turnkey replacement services, including on-site surveying, new cabinet design, installation and commissioning.

Rated value and selection reference

When upgrading, it is necessary to ensure that the new controller is compatible with the voltage and current levels of the existing power section. The following are some specifications of GE BDM series air-cooled DC drives (as a reference for replacing power stacks):

Model Input Voltage Vac Rated Current A 150% Overload (60s) A 200% Overload (60s) A Power kW Weight kg

BDM4-250 183Vac / 229Vdc 322 483 532 137 46.7

BDM4-525 575Vac / 700Vdc 357 480 - 288 104.8

BDM4-1200 846Vac / 1097Vdc 610 976 - 581 112.9

For higher voltages (6000V) or greater power (2500kW), a cabinet style integrated system with UL/CE certification can be provided.

Selection suggestion:

If you want to keep the existing motor and transformer, when upgrading the control part, you can choose PECe+PIBe without replacing the power stack.

If the original power stack has aged or has insufficient capacity, a new BDM series can be chosen to replace it, and its mechanical dimensions are compatible with common old-fashioned DC cabinets.