Reliable power starts with stable excitation. At React Power Solutions, we help operations managers maintain consistent performance through generator excitation systems that match the specific needs of their facility. Whether your application involves standby generators, continuous power systems, or industrial-grade equipment, understanding how excitation works is essential for maintaining voltage stability and output control.
This guide covers core excitation methods, key components like the automatic voltage regulator, and tips for selecting the right system for your application.
What Is Generator Excitation?
Generator excitation supplies power to the rotor winding of a generator using direct current (DC). This creates the magnetic field needed to induce voltage in the stator windings. The stronger and more stable this magnetic field, the more consistent your generator’s output.
Excitation control systems are essential to maintain voltage stability, manage reactive power, and keep your power system running safely and efficiently.
How Excitation Systems Work
All generator excitation systems use a combination of three parts:
- Power Input Source – Can come from the generator output, a dedicated winding, or a separate magnet generator.
- Automatic Voltage Regulator (AVR) – Monitors output voltage and adjusts excitation current as needed.
- Exciter – Delivers field current to the field winding of the rotor.
The AVR supplies DC to the exciter, which then energizes the rotor winding. This interaction generates voltage in the stator. The stability of this process is what keeps sensitive equipment protected from voltage dips and spikes.
Common Excitation Methods
1. Shunt Method (Self-Excited)
How it works: The shunt method uses the generator’s own output voltage as a power source for the AVR. This means the system must build up residual magnetism to function after startup.
Pros:
- Cost effective design
- Fewer components
- Simple setup
Cons:
- Unstable during voltage drops
- Not ideal for non-linear or motor loads
Best Use: Backup systems with basic, steady-state loads and no critical voltage sensitivity.
2. Excitation Boost System (EBS)
The excitation boost system improves on the shunt method by adding hardware to support the AVR during load spikes or startup surges.
Key components:
- Excitation Boost Generator (EBG): Shaft-mounted unit that generates auxiliary power.
- EBC control module: Regulates and activates boost power during load transitions.
How it works:
- The EBG sends power to the regulator AVR to supply more DC to the exciter.
- The boost enables short-term high current output during start-up or fault conditions.
Pros:
- Reliable under sudden load
- Delivers up to 300% short-circuit current
- Supports cost effectiveness without upgrading to a PMG
Best Use: Standby generator systems for commercial or residential buildings.
3. Permanent Magnet Generator (PMG)
A permanent magnet generator is a separate power source dedicated to supplying stable AC power to the AVR, regardless of load conditions.
How it works:
- PMG spins with the generator shaft and creates a separate voltage stream.
- This stream powers the automatic voltage regulator, ensuring stable control.
Pros:
- Steady supply of DC output for field excitation
- Immune to voltage drops during load spikes
- Works well for continuous power applications
Cons:
- Increases system size and cost
- Adds mechanical components that require periodic inspection
Best Use: Data centers, manufacturing plants, or industrial sites with frequent motor starts or high inrush current.
4. Auxiliary Winding (AUX)
An auxiliary winding provides an extra winding inside the generator’s stator. It creates a dedicated AC power supply for the AVR without relying on the main output or an external generator.
How it works:
- AUX winding generates stable voltage while the generator runs.
- This voltage is used by the AVR to supply DC for excitation.
Pros:
- Lower maintenance compared to shaft-driven components
- Good for harsh environments (e.g., marine or offshore)
- Solid alternative to PMG setups
Cons:
- Can’t deliver power until generator reaches operational speed
- Not ideal for rapid transient response
Best Use: Marine power systems, offshore platforms, and industrial generators with space or weight constraints.
Automatic Voltage Regulators (AVRs)
The automatic voltage regulator is the heart of the excitation system. It controls how much power the exciter delivers to the field winding, maintaining output voltage even during varying loads.
Types of AVRs:
- Silicone Controlled Rectifier (SCR): Uses phase-controlled switching to convert AC to DC. Common in systems with consistent loads.
- Field Effect Transistor (FET): Uses pulse-width modulation for fast, high-resolution voltage control. Ideal for systems with frequent load changes or non-linear equipment.
Choosing the right AVR depends on whether the system needs fast response, minimal distortion, or high accuracy for sensitive loads.
Excitation and Reactive Power Control
Excitation systems are not just about keeping voltage stable — they also help control reactive power (VARs), which protects equipment and supports grid health.
- Over-excitation causes the generator to export VARs
- Under-excitation causes it to import VARs
Modern excitation systems can adjust reactive power automatically, especially in generators used for parallel operation or grid-tied setups.
Summary Table: Excitation Method Comparison
| Excitation Method | Power Source | Best For | Key Benefits |
|---|---|---|---|
| Shunt | Generator output | Basic applications | Low cost, simple wiring |
| Excitation Boost System | EBG + EBC control module | Standby/emergency loads | Better voltage stability |
| PMG | Separate magnetic field | Critical/industrial use | Isolated power, stable excitation |
| Auxiliary Winding | Built-in stator winding | Marine/offshore environments | No external hardware, space-saving |
Why Excitation System Choice Matters
The right excitation system ensures:
- Reliable voltage delivery
- Protection against surges and short-circuits
- Efficient generator startup
- Extended equipment lifespan
- Stable operation under dynamic load conditions
If your system experiences voltage fluctuations, slow start-ups, or equipment faults under load, upgrading your excitation method may solve the problem.
Partner with React Power Solutions
At React Power Solutions, we offer power systems built for performance. Whether you need a new unit, a refurbished generator, or service on an existing setup, we carry a full range of diesel and natural gas generators with tested excitation control systems. From shunt excitation to PMG setups, we match your system to your application and deliver ready-to-run units from top brands like Caterpillar, Cummins, Kohler, and Detroit Diesel.
Let us help you choose the best excitation method for your generator. Contact our Houston-based team today for expert support, installation, or parts for your next power system.
