DS3820WGCA - AC Generator Overspeed Control Module

SPECIFICATIONS:

Part Number: DS3820WGCA
Manufacturer: General Electric
Series: Mark IV
Product Type: AC Generator Overspeed Control Module
Input Signal Voltage: 1 – 50 V (peak-to-peak)
Input Frequency Range: 0 – 20,000 Hz
Overspeed Trip Threshold: 110% of rated speed
Power Supply Voltage: 24 VDC / 125 VDC
Trip Response Time: < 10 ms
Operating temperature: –20°C to +60°C
Size: 8.25 cm high x 4.18 cm
Repair: 3-7 days
Availability: In Stock
Weight: 2 lbs
Country of Origin: United States

FUNCTIONAL DESCRIPTION:

DS3820WGCA is an AC Generator Overspeed Control Module manufactured and designed by General Electric as part of the Mark IV Series used in GE Speedtronic Control Systems. These signals are processed through internal frequency-to-voltage converters or digital logic that continuously calculates the generator’s rotational speed. When the calculated RPM exceeds a pre-set overspeed trip threshold—typically defined by ANSI/IEEE protection standards—the module outputs a trip command to the Mark IV logic matrix.

This trip signal is routed to the turbine trip solenoids or protective relays, initiating a generator and/or turbine shutdown within milliseconds. The module is equipped with self-diagnostic features and redundant monitoring paths to support the fault-tolerant architecture of the Mark IV system. It operates in real-time, using hardwired logic and sensor validation routines to ensure fast and accurate response.

The overspeed control module also interfaces with system alarm annunciators and logging functions, enabling operators to track overspeed incidents and confirm shutdown actions. It is powered directly through the Mark IV control cabinet and mounted in the designated rack with other protection and control modules, ensuring full compatibility with the Speedtronic control environment.

WIRING DIAGRAM OF OVERSPEED PROTECTION:

In the GE Speedtronic Mark IV system, the AC Generator Overspeed Control Module is installed in the control panel rack, interfaced through terminal boards (typically TBQA, TBQB, or TBCI, depending on configuration). The wiring architecture consists of the following key elements:

• Input Wiring: Speed sensors (e.g., magnetic pickups) are wired to the overspeed module via shielded twisted-pair cables to minimize electromagnetic interference. These sensors generate a variable-frequency AC signal proportional to the rotational speed of the turbine shaft.

• Signal Conditioning: The raw AC pulses enter the module’s conditioning circuitry, which includes amplifiers, filters, and zero-crossing detectors to convert the signal into clean, logic-level pulses for accurate RPM calculation.

• Power Supply Wiring: The module draws power from the Mark IV power distribution unit, typically 125V DC or 24V DC, depending on module design, and is protected by inline fuses or circuit breakers.

SIGNAL FLOW OF AC GENERATOR OVERSPEED CONTROL MODULE:

• Speed Signal Input: Magnetic pickup(s) mounted on the turbine shaft detect gear teeth or notches, producing a frequency signal proportional to RPM.

• Input Processing: These signals are fed into the overspeed module, where they are filtered, amplified, and shaped into square waveforms.

• RPM Calculation: A high-speed digital counter/timer inside the module measures the pulse frequency and continuously compares it against a preset overspeed threshold.

• Logic Comparison: When the frequency exceeds the threshold (e.g., 110% of rated speed), internal logic asserts an overspeed condition.

• Trip Output Generation: The module activates a solid-state or relay-based trip output that sends a hardwired trip signal to the Mark IV’s protective relay circuit.

• System Shutdown: The trip signal de-energizes the trip solenoids (e.g., ETS – Emergency Trip Solenoids) connected to fuel shutoff valves and steam inlet actuators, forcing the turbine to shut down.

WOC maintains the largest inventory of Replacement parts for GE Speedtronic Turbine Control Systems. Additionally, we offer warranty-backed unused and rebuilt boards as well as board repairs for your damaged ones. For your OEM needs, our team of professionals is available around the clock. We at WOC are happy to help you with any needs you may have in terms of automation. Please contact our team by phone or email for pricing and availability on any components and repairs.

FREQUENTLY ASKED QUESTIONS:

What does an AC Generator Overspeed Control Module do?

It monitors the turbine generator’s rotational speed and triggers a trip command if the speed exceeds a safe limit (typically 110% of the rated speed), helping prevent mechanical damage or system failure.

How does the module detect overspeed conditions?

It receives frequency signals from magnetic pickup sensors mounted on the turbine shaft. These signals are converted and analyzed to determine RPM. If the RPM crosses the overspeed threshold, a trip signal is generated.

What type of input signals are supported?

The module accepts AC signals from speed sensors with a voltage range of 1–50 V peak-to-peak and a frequency range from 0 to 20,000 Hz.