Basler CBS 310/320 Current Boosting System

Basler CBS 310/320 Current Boosting System: Full Analysis of Technical Principles and Engineering Applications

System Overview and Model Differentiation

The CBS current boosting system is an external auxiliary excitation module designed for the Basler APR series voltage regulator. Its core function is to extract energy from the generator output current when the generator terminal voltage drops significantly due to faults or heavy loads, providing additional DC current to the excitation winding to ensure that the regulator can still output sufficient strong excitation voltage.

The system consists of two major components:

Current Boost Module: It contains electronic control circuits, rectification and switching components, status indicator lights, and terminal blocks, all enclosed in a fully sealed metal casing.

Current Transformer (CT): Installed on the output lines of phases A and C of the generator, it provides an input current source for the boost module.

The CBS series includes two models:

Model matching regulator output voltage applicable scenarios

CBS 310 APR63-5 90-120 Vdc Low Voltage Excitation System (12.5 Ω– 50 Ω Magnetic Field)

CBS 320 APR125-5 180-240 Vdc High Voltage Excitation System (25 Ω– 100 Ω Magnetic Field)

Engineering Tip: For old units with APR63-5 serial number 2112 and below, CBS 344X should be used as a substitute model. In addition, the CBS 310 has been replaced by the smaller and lower cost CBS 305, and new design or renovation projects should prioritize the CBS 305.

Technical specifications and key parameters

1. Input and output power

CT input capability: 7A continuous/46A (30 second short duration)

Regulator trigger signal: 10 mAdc @ 1.5 Vdc (taken from the CB+/CB - terminals of APR)

Boost output: CBS 310 is 7.2-9.6A @ 90-120Vdc; CBS 320 is 7.2-9.6A @ 180-240Vdc

The power consumption in non boost state is only 24W, and the standby loss is extremely low

2. Suitable range of excitation winding resistance

CBS 310：12.5Ω ≤ R_field ≤ 50Ω

CBS 320：25Ω ≤ R_field ≤ 100Ω

Exceeding this range may result in insufficient boost output or module overload, which needs to be resolved by connecting resistors in series or replacing the appropriate model.

3. Selection of matching CT

The manual provides three CT specifications, which can be selected according to the rated current of the generator:

CT part number adaptation model maximum continuous current secondary turns

BE 21331-001 CBS 310 Special 800 A 209 turns

BE 21433-001 CBS 310/320 Universal 800 A 209 turns

BE 21432-001 CBS 310/320 universal 2400 A adjustable (see selection table)

Working principle and control logic

1. Trigger mechanism

The CBS module itself does not actively regulate the voltage, but passively responds to the strong excitation command of the APR regulator. When APR detects a voltage drop and outputs a strong excitation signal, its CB+and CB - terminals provide a trigger signal of approximately 1.5V/10mA to the CBS module, causing the static switch inside the CBS to conduct and directing the CT induced current into the excitation circuit.

2. Energy source and fault support capability

Three wire/four wire generator: CBS supports continuous excitation supply in case of single-phase and multi-phase line faults.

Four wire generator phase neutral fault: A phase and C phase faults can be fully supported; The B-phase fault is due to the APR input being taken from the other two phases, which still have partial support capability but are not fully loaded.

Tracking the underfrequency curve: The boost level of CBS automatically follows the underfrequency compensation curve of APR, ensuring coordinated recovery of voltage and frequency during a single loading.

3. Response speed

The strong excitation signal from APR to CBS output reaches 90Vdc, with a response time of less than 2 power frequency cycles (i.e.<33ms @ 60Hz), meeting the fast excitation requirements for the initial short circuit.

CT turns ratio selection engineering calculation (core link)

The success or failure of CBS's on-site application depends on the correct selection of CT turns ratio. The manual provides a detailed engineering calculation process, which can be divided into two paths: "standard selection" and "precise selection".

1. Determination of basic parameters

Strong excitation voltage E: CBS 310 takes 90 Vdc, CBS 320 takes 180 Vdc

Short circuit excitation current:

IField=E/RF (RFR F is the excitation winding resistance)

Based on this current value, the corresponding three-phase short-circuit current can be obtained from the short-circuit saturation curve (excitation current → short-circuit current) provided by the generator manufacturer.

2. Result judgment and selection path

The judgment result adopts a path explanation

The short-circuit current is too high (exceeding the acceptable value), and path 3A needs to be connected in series with a current limiting resistor to reduce the excitation current

Acceptable short-circuit current path 3B can be selected directly according to the table

3. Standard Selection Table (excerpt from Table 2-1)

Column 1: Range of three-phase short-circuit current

Column 2: CT maximum continuous current capacity (not less than generator full load current)