Siemens K4BZ0168456 Excitation Controller Unit

Module Feature

K4BZ0168456 is a dedicated excitation control printed circuit board under Siemens generator excitation system.

It collects generator terminal voltage, CT current signal, compares with voltage setting value, outputs trigger pulse to control thyristor rectifier bridge, realizes automatic voltage regulation and reactive power adjustment. It integrates overexcitation, underexcitation, overvoltage and loss-of-field protection logic, supports 4-20mA analog and dry contact signal for status upload, can work in automatic and manual excitation modes. It is commonly used as spare part for legacy large generator excitation cabinets in thermal power and combined cycle power stations.

Working principle

The sampling circuit collects generator PT voltage and CT current signal and sends to main processing chip.

The controller calculates the deviation between actual voltage and target setpoint, adjusts firing angle of the thyristor rectifier, changes excitation winding current to stabilize generator output voltage. When abnormal operating condition occurs, the board will trigger excitation limit or trip signal to protect generator from damage.

Onboard components

Signal sampling circuit, DSP main control chip, thyristor pulse trigger unit, analog input/output circuit, relay alarm output module, power isolation module, status indicator group, edge connector terminal.

LED indicators

Front LEDs indicate power normal, automatic excitation mode, manual mode, pre-limit warning and protection fault action status.

Hardware self‑diagnosis

Built-in supervision detects PT signal loss, CT unbalance, trigger channel fault, board power failure and communication anomaly. Fault codes can be read via excitation system host HMI.

Programming software

Siemens excitation commissioning software, used for voltage curve setting, excitation limit parameter configuration, event log query and board calibration.

Electrical & Process Parameters

Model:K4BZ0168456 Brand:Siemens Device type:Generator AVR excitation control PCB board Function:Automatic voltage regulation and excitation control for synchronous generator set

Mechanical & Structure

Mounting:Plug-in rack installation inside excitation cabinet Protection class:IP20 Housing:PCB with metal front panel

Environmental

Operating temperature:-20℃ ~ +70℃ Storage temperature:-40℃ ~ +85℃ Ambient humidity:5~95% non‑condensing

Certification:CE, IEC

Status:Legacy Siemens power generation spare

Installation

Check backplane bus and signal wiring before inserting the board into rack slot.

Set voltage reference and excitation limit parameters according to generator nameplate data, perform no-load voltage test before grid connection commissioning.

Interface

PT/CT signal input terminal, pulse trigger output terminal, 24VDC auxiliary power, analog 4-20mA terminal, alarm relay dry contact, communication port.

Diagnostic

Generator voltage unstable: PT sampling wiring loose, board parameter drift or trigger pulse loss. Over-excitation alarm: Reactive power overload, voltage setpoint too high or excitation limit setting error. No excitation output: Board power loss, trigger circuit damage or thyristor bridge fault.

Product Brief

Siemens K4BZ0168456 excitation control board, generator AVR voltage regulator PCB spare for steam and gas turbine generator excitation cabinet replacement.