Description
⚙️ Product Overview
The SELCO T4800-45 is a T4800 Load Sharer designed for automatic active-load sharing and system frequency control between generators operating in parallel. It is intended primarily for generator sets using conventional mechanical governors and relay-based speed adjustment.
The T4800 continuously compares generator active load with the common load-sharing reference and provides increase/decrease control pulses to the governor. It also incorporates reverse-power protection and an unload function that can be used to reduce generator load before breaker tripping.
🔧 Key Features
- SELCO T4800 Load Sharer
- Model/configuration: T4800-45
- Automatic active-load sharing
- System frequency control
- Relay-based governor speed control
- Increase and decrease pulse outputs
- Two-wire communication between T4800 units
- Built-in reverse-power protection
- Generator unload function
- Automatic unload trip capability
- Front-panel LED indication
- Suitable for parallel generator operation
- Designed for marine and land-based generator systems
- DIN-rail or screw mounting capability
📋 Product Datasheet
| Parameter | Specification |
|---|---|
| Brand | SELCO |
| Model | T4800-45 |
| Product Series | T4800 Load Sharer |
| Product Name | Load Sharer Relay Unit |
| Main Function | Active Load Sharing & Frequency Control |
| Control Type | Relay-Based Governor Control |
| Application | Parallel Generator Operation |
| Communication | 2-Wire Load-Sharing Communication |
| Protection | Reverse Power / Unload Trip |
| Operating Temperature | -20°C to +70°C |
| Mounting | DIN Rail or Screw Mounting |
| Vibration Resistance | Up to 4g RMS |
| Condition / Status | Verify actual unit condition |
| Dimensions | Verify exact T4800-45 enclosure configuration |
| Weight | Approx. 0.9 kg class; verify actual unit |
| Power / Voltage Rating | Configuration-dependent; verify nameplate |
⚡ Load-Sharing & Governor Control
The T4800 is designed for generators operating in parallel with other generators or with a utility grid. Each load sharer measures generator voltage and current, determines the active load, and compares it with the load-sharing reference.
When the generator load is outside the desired balance point, the T4800 activates its INCR. or DECR. relay outputs. These pulses can drive a conventional governor’s servo motor or be passed through an E7800 Motorized Potentiometer when interfacing with an electronic speed controller.
The regulation characteristics can be adjusted through the stability and load/frequency settings. SELCO documentation specifies a system-frequency adjustment range of approximately 48–62 Hz and adjustable proportional/dead-band characteristics.
🔌 Communication & Protection Functions
Multiple T4800 units can communicate through their common load-sharing connections. The parallel-line signal allows the controllers to coordinate generator loading so that generators share active power according to their individual capacities.
The unit also provides reverse-power protection with selectable trip limits and time delays. The unload function can reduce generator load toward zero, after which a potential-free trip contact can be used to initiate circuit-breaker tripping.
For applications requiring both active and reactive load sharing, SELCO identifies the T4900 VAr Load Sharer as a complementary product to the T4800.
🚢 Typical Applications
The SELCO T4800 can be used for:
- Marine generator control systems
- Shipboard power-generation systems
- Diesel generator paralleling
- Generator-to-generator load sharing
- Generator-to-grid operation
- Auxiliary generator systems
- Standby power plants
- Industrial generator installations
- Conventional mechanical governor systems
- Generator retrofit and replacement projects
SELCO identifies the T4800 as suitable for both marine and land-based applications and notes certification by major marine classification societies.
🛠️ Installation & Maintenance
Before replacing a T4800, verify the complete unit designation and electrical configuration. Different T4800 variants are available for different system voltages and current-transformer inputs.
- Shut down the affected generator according to the site procedure.
- Isolate the T4800 supply and generator control circuits.
- Record all existing terminal connections.
- Verify voltage, CT input, and model/configuration markings.
- Check the phase sequence and current-transformer polarity.
- Install the replacement unit securely.
- Reconnect the load-sharing communication lines.
- Verify the INCR./DECR. governor connections.
- Restore power and check the front-panel indications.
- Test load sharing, frequency control, unload, and reverse-power functions under controlled conditions.
SELCO documentation emphasizes correct voltage/current phase relationships and CT polarity. Incorrect connections can cause incorrect load-sharing behavior or drive the generator toward excessive or reverse power.
🔍 Troubleshooting Guide
Generator load does not balance:
Check CT polarity, phase sequence, current-transformer phase selection, and the common load-sharing connections.
Generator moves toward reverse power:
Check the polarity of the measured current and voltage signals and verify that the generator-side reference is correctly connected.
INCR./DECR. relays do not operate:
Check the load/frequency deviation, governor wiring, relay outputs, and front-panel LED indications.
Frequency control is incorrect:
Verify the system-frequency setting and any external synchronizer or frequency reference connection.
Unload function does not initiate breaker trip:
Check the unload input, load level, trip relay wiring, and breaker control circuit.
❓ Frequently Asked Questions
Q: What is SELCO T4800-45?
A: It is a T4800-series load-sharing relay/control unit for automatic active-load sharing and frequency control of parallel generators.
Q: Is the T4800 designed for electronic governors?
A: The T4800 is primarily designed for conventional governors using relay-based increase/decrease pulses. An E7800 Motorized Potentiometer can be used to adapt the pulse output for certain electronic speed-control arrangements.
Q: Can several T4800 units work together?
A: Yes. The T4800 uses a two-wire communication arrangement to exchange load-sharing information between multiple units.
Q: Does the T4800 provide reverse-power protection?
A: Yes. Reverse-power protection is built into the T4800 and provides selectable limits and time delays.
Q: Can the T4800 unload a generator?
A: Yes. Its unload function reduces generator load toward zero and can provide a trip signal for the circuit breaker.
Q: Is T4800 suitable for marine applications?
A: Yes. SELCO specifically identifies the T4800 for marine applications and lists certification by major marine classification societies.
📦 Recommended SELCO Models
- SELCO T4800 – Load Sharer for Conventional Governors
- SELCO T4800-0010 – 400/450V, 5A Load Sharer
- SELCO T4800-0020 – 230V, 5A Load Sharer
- SELCO T4800-0030 – 415/480V, 5A Load Sharer
- SELCO T4800-0040 – 100/110V, 1A Load Sharer
- SELCO T4800-0050 – 400/450V, 1A Load Sharer
- SELCO T4800-0060 – 120/127V, 5A Load Sharer
- SELCO T4800-0070 – 100/110V, 5A Load Sharer
- SELCO T4400 – Load Sharer for Electronic Speed Controllers
- SELCO T4900 – VAr Load Sharer
📌 Spare-Part Recommendation
For replacement planning, match the complete T4800-45 identification and the actual electrical configuration rather than selecting a T4800 solely by series name. Confirm system voltage, CT input rating, phase arrangement, governor interface, and existing load-sharing wiring before installation.
The T4800 is particularly useful as a maintenance spare for marine and industrial generator systems where conventional governor control and automatic active-load sharing are required.
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