What types of loads cause power harmonics, their impacts, and solutions:

https://www.hatchpower.com/posts/loads-causing-power-harmonics 

What types of loads cause power harmonics, their impacts, and solutions:

In commercial and industrial environments, non-linear loads generate harmonics, which can impact power quality, equipment efficiency, and overall operational costs. Here’s a comprehensive overview of the types of harmonic-producing loads, their impacts, and potential solutions.

Common Harmonic-Causing Loads

1.   Variable Frequency Drives (VFDs) with the lower pulse driver.

   Cause: VFDs control motor speeds and require AC-DC-AC conversion, which generates harmonics due to their rectifier if it is design with the lower pulse driver.

   Impacts: Increased heat in motors and transformers, higher maintenance, reduced equipment lifespan, and reduced power factor.

  Solutions:

a)    Active Harmonic Filters: Dynamic filtering to cancel out harmonics.

b)    VFD with the 12-Pulse or 18-Pulse Drives: Reduces harmonics compared to 6-pulse drives.

c)    Line Reactors: Limit harmonic current flowing into the power system.

2.   Uninterruptible Power Supply (UPS) Systems

   Cause: Double-conversion UPS systems introduce harmonics from AC-DC-AC conversions (rectifier bridge) when designed with fewer than 12 pulses. While 12-pulse systems still generate a lower percentage of THDI, they are significantly better than 6-pulse rectifiers.

   Impacts: Reduced efficiency, heating, potential resonance with other equipment fed from the same upstream source, voltage distortion and power factor penalties.

  Solutions:

a)    K-Rated Transformers: Handle higher harmonic currents without saturating.

b)    Active or Passive Harmonic Filters: Clean up harmonics from the UPS.

c)    Dedicated Line Reactors: Limit harmonic currents entering other systems.

3.   LED Lighting and Electronic Ballasts

   Cause: LED drivers and electronic ballasts use power electronics, creating harmonics.

   Impacts: Harmonics contribute to poor power factor, overheating, and transformer inefficiency.

  Solutions:

a)      Low Harmonic Lighting Systems: Choose LED drivers designed for minimal harmonics.

b)      Passive Filters: Block harmonic frequencies on lighting circuits.

c)      Dedicated Circuits or Isolation Transformers: Separate lighting loads from other sensitive equipment.

4.   Computers and Office Equipment

   Cause: Switched-mode power supplies (SMPS) in computers, servers, and copiers draw non-linear current, producing harmonics.

   Impacts: Voltage distortion, overheating in transformers, and reduced efficiency.

   Solutions:

a)    Active Harmonic Filters: Cancel harmonics generated by IT equipment.

b)   Power Factor Correction (PFC) Devices: Improve power factor and reduce distortion.

c)    UPS Systems with Harmonic Filtering: UPS with built-in filters for data centers.

5.   HVAC Systems

   Cause: HVAC equipment with VFDs and electronic controls generates harmonics.

   Impacts: Voltage instability, heating in distribution systems, and power losses.

  Solutions:

a)    Harmonic Filters for VFDs: Install dedicated filters for HVAC drives or selecting advance VFD designed with 12 pulse rectifiers.

b)    Line Reactors: Minimize harmonics by adding inductance.

c)    Higher-Pulse Drives: 12-pulse or 18-pulse VFDs reduce harmonics.

6.   Elevators and Escalators

   Cause: Motor drives and control systems in elevators and escalators introduce harmonics due to variable speeds and high currents.

   Impacts: Increased power losses, interference with other equipment, overheating, and reduced efficiency.

  Solutions:

a)    Isolation Transformers: Separate elevator systems to limit harmonic spread.

b)    Passive Filters: Minimize specific harmonics created by motor drives.

c)    Regenerative Drives: Modern drives can reduce harmonics and feed power back to the grid.

7.   Industrial Machinery and Robotics

   Cause: Electric drives and controls in industrial machinery draw non-linear currents, producing harmonics.

   Impacts: Reduced motor life, power system instability, and higher operating costs.

  Solutions:

a)    Active Filters: Provide dynamic filtering for variable harmonic levels.

b)    DC Bus Filters: Absorb harmonics within DC drives before they reach the AC system.

c)    Custom Filtering Solutions: Specific filters designed for each machine’s unique harmonic profile.

8.   Arc Furnaces and Welding Equipment

   Cause: Arc furnaces and welding machines create high levels of harmonic distortion due to non-linear, high-current arcs.

   Impacts: Severe power quality issues, flicker, voltage drops, overheating, and resonance problems.

  Solutions:

a)    Dedicated Power Supply: Separate transformers for welding and furnace loads.

b)    Active Harmonic Compensators: Specialized compensators for high-current harmonic reduction.

c)    Power Conditioning Equipment: Such as voltage restorers to control flicker and harmonics.

9.   Battery Chargers and EV Charging Stations

   Cause: Chargers for electric vehicles and other battery systems create harmonics due to AC-to-DC conversion (Rectifier bridge).

   Impacts: Overloading and voltage distortion of back feed transformers, higher energy costs, heating, and possible grid interference.

  Solutions:

a)    Active Harmonic Filters: Effective for dynamic harmonic compensation.

b)    Multi-Pulse Chargers: 12 or 18-pulse chargers reduce harmonic emissions.

c)    Dedicated Transformers: Isolate chargers to prevent harmonic spread.

10.    Renewable Energy Systems (Inverters)

   Cause: Solar PV and other renewables use inverters for DC-AC conversion, introducing harmonics.

   Impacts: Voltage distortion, transformer heating, and reduced power quality.

  Solutions:

a)    Low Harmonic Inverters: Inverters with low harmonic design reduce interference.

b)   Active Harmonic Filters: Mitigate harmonics generated by variable energy inputs.

c)    Isolation Transformers: Prevent harmonic propagation to sensitive building loads.

Summary of Harmonic Impacts and Solutions

• Impacts of Harmonics:

o  Power Losses: Harmonics increase I²R losses, leading to higher energy costs.

o  Overheating: Transformers, cables, and motors may overheat, shortening their lifespan.

o  Equipment Malfunctions: Sensitive devices may malfunction or fail under harmonic distortion.

o  Voltage Distortion: Harmonics affect voltage waveforms, disrupting power quality.

o  Interference: Harmonics can cause electromagnetic interference with other devices.

o  Power Factor Penalties: Utilities may impose penalties for low power factor due to harmonics.

Ø  General Solutions for Harmonic Reduction:

o  Passive Harmonic Filters: Affordable and effective for specific harmonics.

o  Active Harmonic Filters: Dynamically compensate for a broad range of harmonics.

o  Line Reactors and Chokes: Simple, cost-effective for certain loads like VFDs.

o  12-Pulse or 18-Pulse Equipment: Reduces harmonics by canceling out certain frequencies at the source.

o  Isolation Transformers: Contain harmonics within specific systems, reducing spread to other loads.

o  Power Factor Correction Devices: Improve power factor and mitigate harmonics.

A power quality analysis is often essential to identify the types and severity of harmonics present and determine the most effective mitigation strategy tailored to the facility’s specific needs.