Understanding Nonlinear Loads and Their Impact on Diesel Generators
Modern backup power systems often encounter nonlinear electrical loads, which can significantly impact generator performance. This article explains what nonlinear loads are, how they affect diesel generators, and how to manage them effectively.
What Are Nonlinear Loads?
Unlike linear loads, which draw a smooth, sinusoidal current, nonlinear loads draw current in bursts or irregular patterns. This creates harmonic distortion in the electrical system.
Common Nonlinear Loads:
- Computers and servers
- LED lighting with unfiltered ballasts
- Battery chargers
- Variable Frequency Drives (VFDs)
- UPS systems
Why Are Harmonics a Problem?
Harmonics distort the electrical waveform, causing Total Harmonic Distortion (THD). This leads to:
- Overheating of generator and equipment
- Malfunctioning sensitive electronics
- False breaker trips
- Shortened generator lifespan
VFDs: Efficiency at a Cost
VFDs provide energy savings and precise motor control, but they introduce harmonic distortion. This must be factored into generator sizing and system design.
Generator Sizing for Nonlinear Loads
Proper generator sizing must consider:
- Subtransient Reactance (Xd”) – Lower values improve tolerance to harmonics
- Load composition – Higher nonlinear load ratios cause more THD
- Voltage and frequency tolerance – Particularly during motor starts or load switching
Harmonic Mitigation Strategies
- Passive filters – Simple but limited
- Active filters – More effective but costly
- 12- or 18-pulse VFDs – Produce fewer harmonics
- Oversizing the generator – Reduces nonlinear load ratio
Industry Guidelines
IEEE 519 sets recommended THD limits and defines the Point of Common Coupling (PCC) as a measurement location. In generator systems, this is typically the Automatic Transfer Switch (ATS).
Summary
Understanding nonlinear loads and their effects is key to designing reliable backup power systems. At Aurora Generators, we build diesel generators equipped to handle these challenges. Contact us to ensure your generator is properly sized and specified.