What is Electrical Inrush Current?
What is inrush current? The definition of electric inrush current is the maximum instantaneous input current drawn by an electrical devices when it is first turned on. Another definition of inrush current is a momentary current surge that occurs when the electricity device is turned on. This article will discuss source that cause of inrush current, effect and mitigation technique of inrush current. It also briefly describe the difference between inrush current and starting current. — Omazaki Consultant is a consultant company who provides power quality studies consulting and analysis to audit and assessment services for commercial and industrial facilities. If you are looking for power quality study consultants service for your project, include sensitive electronic equipment, in Indonesia and South East Asia, please contact us by sending an email to email@example.com or by filling in the form in contact.
Inrush Current Categories
Inrush current can be classified to three categories as follows:
- Energization inrush —Energization inrush current is mainly produced due to multiple times energization of power transformer (switching phenomena). This results due to residual flux (remanance) which always remains in core of transformer due to ferro magnetic properties of the transformer core material.
- Recovery inrush —This is type of inrush current is mainly generated when applied voltage to the power transformer is becoming normal (restore) after being subjected to the some kind of system disturbances (fault appearance) and upon its complete removal.
- Sympathetic inrush —This type of inrush current is mainly seen in power system when numbers of transformers are connected parallel and another one is energized to connect across it. That newly energized transformer creates disturbance in the magnetic field of the remaining transformers of network.
Factors Affecting the Inrush Current
Some factors which are responsible for inrush current in transformer are:
- Switching angle
- Residual flux density
- Series resistance
- Source impedance
- Inrush under load
Inrush Current vs Starting Current
Inrush current and starting current are related but distinct concepts in the context of electrical systems. Inrush current refers to the momentary surge of current that occurs when an electrical device is first turned on. This surge is typically higher than the device’s steady-state operating current. On the other hand, starting current specifically refers to the initial current drawn by an electric motor when it is first started. Starting current is often higher than the motor’s rated operating current and is necessary to overcome the initial inertia and bring the motor up to its operating speed.
In brief, electric inrush current is a broader term that encompasses the initial current surge in various types of electrical devices, while starting current specifically refers to initial current drawn by electric motors during startup.
Sources of Inrush Current
Sources of electrical inrush current are:
- Power transformers, especially toroidal types of 500VA or more
- Power supplies that obtain a low voltage AC from a transformer
- Electric motors of all types, with the greatest problems caused when starting under load from rest
- Incandescent lamps using a tungsten filament (AC or DC powered, any voltage)
- Fluorescent and other gas discharge lamps (including compact fluorescent types)
- Heating elements
- Electronic power supplies, as commonly used for personal computers, wall supplies, etc.
- Electronic power supplies with active power factor correction (PFC).
Effect of Inrush Current
Some common effect of excessive electric inrush current are:
- Cause voltage drops in the electrical system, potentially leading to malfunctions or disruptions in the operation of sensitive equipment
- Cause nuisance faulting of circuit breakers (CB) or fuses to blow, resulting in downtime and potential damage to equipment.
Inrush Current Mitigation Techniques
- Asymmetrical winding design
- Using series compensator
- Sequential phase energization method
- Controlled switching method
- Virtual air gap
- Pre fluxing method
- Using ultra low frequency power source
- Bidirectional impedance type transformer inrush current limiter.
Contact Omazaki Consultant if you are looking for a power quality audit, assessment, study and analysis consulting services consultant to help your project or existing electrical system more efficient and reliable in Indonesia and South East Asia.
- Electrical Power System Study
- Power System Transient Stability Study
- Causes Effect Solution of Transient in Industrial
- IEEE 1159-2019 IEEE Recommended Practice for Monitoring Electric Power Quality
- IEC 61000-4-30 Testing and Measurement Techniques – Power Quality Measurement Methods
- Inrush Current in Transformer and Its Mitigation – Roopal R Kapadia, Dr.R.M.Patel, Dr. J.J.Patel