Dry-type Step-up Transformer

Updated: 2026-09-12

Overview

A Dry-type Step-up Transformer is an electrical device designed to increase voltage levels in power distribution networks while maintaining isolation between primary and secondary circuits. Unlike oil-filled transformers, it uses solid insulation (e.g., epoxy resin) and air or gas cooling, eliminating fire hazards and environmental risks. These transformers are favored for their reliability in indoor installations, such as data centers, hospitals, and renewable energy systems, where safety and space efficiency are paramount. They comply with international standards like IEC 60076 and IEEE C57.12.01, ensuring consistent performance in diverse operating conditions.

Structure and Working Principle

The transformer consists of a laminated silicon steel core, primary/secondary windings (copper or aluminum), and epoxy resin encapsulation. The core minimizes eddy current losses, while the windings are arranged to achieve the desired voltage ratio (e.g., 1:2 for doubling voltage). When AC current flows through the primary winding, it induces a magnetic field in the core, which in turn generates a higher voltage in the secondary winding. The absence of liquid coolant simplifies maintenance and allows for compact designs, such as cast resin or vacuum pressure impregnated (VPI) models.

Key Features

Dry-type transformers offer flame-retardant properties due to their epoxy or silicone insulation, making them suitable for confined spaces. They operate with efficiency levels of 95–98%, reducing energy waste compared to older oil-based units. Advanced models include temperature sensors (PT100) and cooling fans for overload protection. Their noise levels are typically below 65 dB, and they withstand short-circuit currents without explosive failures, per IEC 60076-11 standards.

Application Areas

Common applications include solar/wind farms (step-up for grid integration), industrial machinery (e.g., CNC equipment), and commercial buildings (HVAC systems). They are also deployed in mining and marine environments where oil leaks are unacceptable. In renewable energy, dry-type step-up transformers convert low-voltage solar PV output (e.g., 480V) to medium voltage (e.g., 34.5 kV) for grid transmission. Their ability to handle harmonic distortions from inverters makes them ideal for modern power systems.

Maintenance and Precautions

Routine maintenance involves visual inspections for dust accumulation, checking terminal tightness, and monitoring temperature via embedded sensors. Insulation resistance should be tested annually using a megohmmeter (minimum 1 kV test voltage). Avoid installation in humid or corrosive environments without proper enclosures (IP21–IP65 ratings). Ensure adequate clearance for airflow—manufacturers typically specify 300–500 mm around the unit. Overloading beyond nameplate ratings can degrade insulation prematurely.

B2B Procurement Guide

When sourcing dry-type step-up transformers, verify compliance with regional standards (e.g., UL 5085 in North America, CE in Europe). Key specifications include rated power (kVA), voltage ratio, impedance (typically 4–6%), and insulation class (F or H for high-temperature resilience). Leading manufacturers include ABB, Siemens, and Schneider Electric. For custom projects, provide load profiles, ambient conditions, and harmonic content data. Bulk procurement (10+ units) may yield 10–15% cost reductions. Lead times range from 8–12 weeks for standard models.