SNTOOM Electrical Co., Ltd. | Protecting Electrical Safety

Parallel Operation of Transformers: The Conditions That Must Match

2026-10-13 No Comments

Adding a second transformer beside an existing one looks like the cheapest route to more capacity. It often is, but only when four conditions line up exactly: turns ratio and tap position, vector group, impedance voltage and phase sequence. Where they do not, the result is not reduced capacity but circulating current flowing between the units before any load is connected, heat that appears with no explanation, and protective devices that operate without a fault. This article sets out each condition, what happens when one of them is not satisfied, and a five-step check for a proposed pairing that can be carried out before energisation.

Harmonic Currents and K-Factor: Sizing a Transformer for Non-Linear Loads

2026-10-13 No Comments

A transformer feeding a plant full of variable frequency drives can run dangerously hot while a clamp meter reads less than its rated current. Harmonic currents are the reason a transformer k-factor exists as a separate specification. This article explains why non-linear loads heat a transformer more than their current suggests – eddy current losses rise roughly with the square of frequency, so the extra heat appears in the windings while the fundamental current stays below the kVA rating – what a K-factor rating does and does not guarantee, why neutral conductors need separate attention under triplen harmonics, and how to size for harmonic currents using measured total harmonic distortion, a load profile, a matched K-factor and a derating factor for the real plant room.

Transformer Altitude Derating: Why Thin Air Reduces Capacity

2026-10-13 No Comments

A unit ordered for a coastal plant and the same unit installed at 2,500 m are not the same machine in service, even when the nameplate reads identically. Air density falls with height, and thinner air does two jobs less well: it carries heat away from the windings, and it insulates. This article explains what physically changes at height – cooling capacity and dielectric strength – how the altitude correction factor is applied, either by reducing the permissible temperature rise or by raising the insulation requirement, and what should be confirmed on the enquiry: the real site elevation, the reference conditions behind the quoted rating, whether the kVA figure is the sea-level or the corrected value, and the ventilation design at the corrected load.

Transformer Selection: Seven Parameters Industrial Buyers Often Overlook

2026-10-13 No Comments

Transformer selection is usually treated as a single question: what kVA rating do I need? The parameters that cause the most expensive mistakes rarely appear on a quotation. This article explains how ambient temperature and site altitude change the rating a transformer can actually deliver, how the load profile of the plant – continuous versus cyclic duty, future load growth, harmonic content and the cost of oversizing – decides where to sit below the kVA ceiling, and which electrical checks should be completed before the order is placed: vector group, impedance voltage, tap range, insulation class and the written confirmation of derating. Getting these right at the enquiry stage costs one line; correcting them afterwards costs a transformer.

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Parallel Operation of Transformers: The Conditions That Must Match

Harmonic Currents and K-Factor: Sizing a Transformer for Non-Linear Loads

Transformer Altitude Derating: Why Thin Air Reduces Capacity

Transformer Selection: Seven Parameters Industrial Buyers Often Overlook

Provide you with high-quality and reasonably priced products

Commercial and Industrial Ventilation Equipment & Solution

Industrial Fans

Alarm Security Series

Power Equipment

Committed to providing customers with high-quality electrical products

Committed to a greener, safer world

Need help?

Need a quotation？

Want to learn more？

Want to become a partner？

Electrical Solutions

Iron and Steel Metallurgy

Signal Tower

Lifting machinery

Ports and Terminals

Exploring the frontiers of electrical technology

Parallel Operation of Transformers: The Conditions That Must Match

Harmonic Currents and K-Factor: Sizing a Transformer for Non-Linear Loads

Transformer Altitude Derating: Why Thin Air Reduces Capacity

Transformer Selection: Seven Parameters Industrial Buyers Often Overlook

Provide you with high-quality and reasonably priced products

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