Description
Product Introduction
The B&W SQ-300i 8700700-006C is an industrial Hybrid Automatic Voltage Control (AVC) controller used in electrostatic precipitator systems. Unlike a conventional PLC I/O module, the SQ-300i is application-specific control equipment intended to regulate the electrical operating point of an ESP transformer-rectifier set. Its purpose is to maintain effective electrical collection performance while responding to operating conditions and system alarms.
The hybrid architecture is significant because the SQ-300i can control either a conventional single-phase T/R set or a three-phase T/R arrangement designed for low ESP voltage ripple. Available technical descriptions also state that the controller analyzes alarms and provides an interface to computer-based data-acquisition software.
For maintenance teams, 8700700-006C should be treated as the complete controller identification. Some online listings describe the unit generically as an industrial control module and publish conflicting specifications such as 24 VDC supply, Modbus RTU, analog I/O, or PLC functionality. Those claims are not consistent with the more specific identification of the unit as a B&W SQ-300i Hybrid AVC.
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Babcock & Wilcox (B&W) |
| Model | SQ-300i |
| Part Number | 8700700-006C |
| Product Type | Hybrid Automatic Voltage Control (AVC) |
| Primary Application | Electrostatic Precipitator (ESP) |
| Controlled Equipment | Transformer-Rectifier (T/R) Set |
| T/R Compatibility | Single-phase conventional / low-ripple three-phase |
| Controller Supply | 120–240 VAC* |
| Communication / Data Interface | Computer-based data acquisition interface* |
| Alarm Function | ESP/T-R operating alarm analysis |
| Control Function | Automatic electrical operating-point control |
| Product Family | SQ-300 |
| Installation | ESP control cabinet |
| Typical Industry | Power generation, process plants, air-pollution control |
*The 120–240 VAC figure is supported by current equipment listings, while several secondary websites publish contradictory electrical specifications. The exact supply and interface wiring should therefore be confirmed against the nameplate and site-specific B&W documentation before engineering use.
Application Scenarios & Engineering Considerations
The SQ-300i is primarily found in electrostatic precipitator control systems, where maintaining the correct electrical conditions across the collecting electrodes is essential for particulate-removal performance.
- ESP transformer-rectifier control: The controller regulates the power delivered to the T/R set rather than functioning as a general-purpose PLC.
- Single-phase T/R applications: The hybrid controller can support conventional single-phase transformer-rectifier configurations.
- Three-phase low-ripple systems: The SQ-300i also supports three-phase T/R arrangements designed to reduce voltage ripple.
- Alarm monitoring: The controller analyzes operating alarms associated with the ESP/T/R system, giving maintenance personnel information about abnormal electrical conditions.
- Plant data acquisition: Available descriptions indicate an interface with computer-based data-acquisition software, allowing operating information to be incorporated into higher-level monitoring systems.
Field note: Poor ESP performance does not automatically indicate a failed SQ-300i. T/R transformer condition, rectifier components, electrode loading, spark activity, insulation, grounding, and secondary-side faults can all produce symptoms that initially appear to be controller-related.
SQ-300I 8700700-006C
Related Products
- B&W SQ-300i / 8700700-006C — The exact Hybrid AVC controller covered here.
- B&W SQ-300 product family — The broader automatic voltage-control platform from which the SQ-300i was developed. The SQ-300i extends the architecture to both conventional and low-ripple three-phase T/R applications.
- B&W Transformer-Rectifier Set — The high-voltage power equipment controlled by the AVC system. The exact T/R configuration must be matched before commissioning a replacement controller.
- ESP Control System — The complete system surrounding the SQ-300i, including the precipitator, T/R set, sensing circuits, grounding, alarm circuits, and plant data-acquisition interface.
The Engineer’s Guide: Field Pitfalls to Avoid
⚠️ Do not treat SQ-300i as a generic PLC controller.
The SQ-300i 8700700-006C is specifically described as a Hybrid Automatic Voltage Control unit for electrostatic precipitators.
How to avoid it: Identify the host ESP system and T/R configuration before selecting a replacement.
⚠️ Do not trust generic online specifications without checking the nameplate.
Several secondary listings give completely different specifications for the same part number, including 24 VDC supply, 0–10 V input, 4–20 mA output, RS-485, and Modbus. These descriptions are inconsistent with the more specific product identification.
How to avoid it: Use the physical nameplate, wiring diagram, terminal markings, and B&W documentation as the engineering reference.
⚠️ Do not replace the controller without identifying the T/R configuration.
The hybrid design specifically supports different T/R arrangements. A controller configured for one system should not be assumed to be ready for another simply because the model number matches.
How to avoid it: Document whether the existing installation uses a conventional single-phase or low-ripple three-phase T/R set.
⚠️ Investigate the secondary circuit before condemning the AVC.
ESP secondary faults, arcing, insulation problems, and abnormal spark conditions can cause repeated controller trips.
How to avoid it: Review the complete fault sequence and inspect the T/R and ESP electrical system before replacing the controller.
Frequently Asked Questions
What is B&W SQ-300i 8700700-006C?
It is a Hybrid Automatic Voltage Control (AVC) controller for electrostatic precipitator systems. It controls the electrical power supplied to compatible transformer-rectifier sets and provides alarm/data-acquisition functions.
What does SQ-300i control?
It controls the power supplied to an ESP transformer-rectifier set and manages the operating conditions required by the precipitator. The hybrid design supports conventional single-phase T/R equipment as well as low-ripple three-phase T/R equipment.
Is SQ-300i a PLC module?
No. It is a dedicated ESP automatic voltage controller, not a conventional PLC CPU or general-purpose I/O module.
What is the part number?
The requested unit is identified as:
SQ-300i — 8700700-006C
What type of equipment uses SQ-300i?
The primary application is electrostatic precipitator (ESP) systems, particularly those using transformer-rectifier power supplies for particulate collection.
What should I verify before purchasing a replacement?
For a plant spare, verify:
- SQ-300i
- 8700700-006C
- Existing B&W ESP system
- T/R set manufacturer and model
- Single-phase or three-phase configuration
- Controller supply voltage
- Existing terminal/wiring arrangement
- Alarm configuration
- Data-acquisition interface
- Firmware/configuration, where applicable
- Nameplate revision
- Functional testing of the controller
