Array transformers, widely used in PV power stations, have always faced a persistent challenge when being connected to the grid for power generation — magnetizing inrush current.

Magnetizing inrush current is the transient surge current generated at the instant a transformer is energized. The voltage sags, protection maloperations, and repeated operation-and-maintenance headaches it triggers are pitfalls almost every PV project has fallen into.

Every routine closing impact erodes the transformer’s insulation lifespan and exposes it to the risk of energization failure caused by excessive inrush current. As a result, array transformers cannot be switched on and off frequently.

When there is no sunlight and the array transformer is not generating power, it can only operate at no load, leaving behind alarming accumulated losses.

A distributed PV power generation project at a steel plant’s slag yard in Liaoning Province faced exactly this thorny problem.

In the early stages of construction, the project did not take the magnetizing inrush current issue into account.

After the project was completed, at the critical stage of boosting voltage and connecting the array transformers to the grid, the transformers tripped the moment they were energized because of magnetizing inrush current, severely hampering progress in grid-connected PV power generation.

To address this challenge, the project adopted GoLead Intelligent’s “Magnetization + Phase Control” solution, which perfectly overcame the technical bottleneck of magnetizing inrush current.

On-Site Overview

On July 16, 2026, the Liaoning project team conducted energization and commissioning tests on two main transformers, No. 2 and No. 3 (rated capacity: 20,000 kVA; rated HV-side voltage: 35 kV).

For the first energization of the transformers, a portable SID-3610 Transformer Flux Conditioning Device was first used to actively magnetize the core, followed by phase-controlled closing with the SID-3YL Inrush Current Suppressor.

After the transformers had operated stably for a period, they were de-energized. For subsequent energizations, phase-controlled closing was performed using the advanced residual-flux algorithm of the SID-3YL Inrush Current Suppressor.


Schematic of the Magnetization + Phase Control Solution

Main Transformer Parameters

No. 2 Main Transformer

No. 3 Main Transformer

See the Effect at a Glance

The commissioning data using the Magnetization + Phase Control solution are as follows:

No. 2 Main Transformer Data

No. 3 Main Transformer Data

The commissioning data clearly show that the transformer’s magnetizing inrush current was suppressed to below 0.14x!

Only When Inrush Is Tamed Can PV Truly “Get Moving”

When a conventional transformer is closed at no load, magnetizing inrush current of 5–8 times the rated current often erupts. This “instant burst” not only threatens equipment lifespan, but also triggers voltage sags and protection maloperations, causing tripping the moment power is applied.

This has long been an operational pain point for PV power stations: at night or on rainy days when no power is generated, the station should be shut down to save electricity, yet for fear of inrush current impact, transformers have to keep idling and consuming power, with operators not daring to switch them off.

With the transformer Magnetization + Phase Control solution, the closing inrush current is suppressed to an astonishing 0.14x. Physical impact is virtually eliminated, and transformers no longer have to “struggle on while unwell.” Only by thoroughly taming this roadblock can PV power stations truly achieve on-demand start/stop, letting every kilowatt-hour of electricity be delivered without burden.

Product Tips

1. SID-3YL Inrush Current Suppressor — Key Highlights

· Supports three-phase gang-operated circuit breakers: the device automatically calculates the residual-flux angle at opening, so that the bias flux of the corresponding phase exactly cancels the residual flux, achieving inrush current suppression without phase-by-phase operation.

· Controlled-opening-free technology: patented online residual-flux monitoring requires no controlled opening, offering greater application flexibility.

· Ultra-high precision: precise phase control for phase-separated / gang operations (±3°).

· Multi-scenario compatibility: adaptable to transformers of different manufacturers and voltage levels, as well as non-linear loads such as capacitor banks and reactors.

2. SID-3610 Transformer Flux Conditioning Device — Key Highlights

· First energization and commissioning after maintenance: active magnetization provides quantitative control of core flux, solving the first-closing and post-maintenance de-magnetization commissioning problems that conventional phase control technology cannot handle.

· High-precision controllable magnetization: patented magnetization technology intelligently calculates based on transformer parameters, delivering precisely controllable magnetization results.

· One-touch operation: no repeated configuration after the initial setup — one touch triggers the magnetization process.

· Non-intrusive installation: easy to install and remove, convenient for on-site deployment.

· Multi-transformer parameter management: supports data storage for multiple transformers, with one device adapting to multiple pieces of equipment.

From the Liaoning steel plant to more new-energy projects, GoLead Intelligent has proven time and again with real-world field data: taming inrush current requires no magic — just hard-core technology. For the magnetizing inrush current impact on array transformers, a single Magnetization + Phase Control solution makes the problem melt away.