SGG-40KVA Dry-Type Isolation Transformer (3-Phase, Three-phase to single-phase)

The SGG-40KVA is a three-phase dry-type isolation transformer providing complete galvanic separation between primary and secondary windings. Unlike autotransformers, it suppresses common-mode noise, blocks voltage transients and eliminates ground-loop interference. Built with F-class insulation, grain-oriented silicon-steel laminations and an electrostatic shield, it delivers ≥95% efficiency, pure sinusoidal output and a 20-year design life.

Ideal for precision CNC machinery, medical diagnostic equipment, semiconductor fabrication, data centre power conditioning, telecommunications, laboratory instruments and any environment where ground-loop elimination and transient protection are critical.

Key Features

• Full Galvanic Isolation: No direct electrical path between primary and secondary

• Electrostatic Shield: >60 dB common-mode noise attenuation

• High Efficiency: ≥95% with pure sinusoidal output

• F-Class Insulation (155°C): Temperature rise ≤70°C at full load

• Dielectric Withstand: AC 3000V / 1 min (primary to secondary)

• Connection Groups: Δ/Y (recommended), D/d, D/y, Y/y, Y/d, Y/yn

• Overload Capability: 1.2× rated load

• Design Life: 20 years, continuous duty

• Customisable Input: ≤600V

• Robust Enclosure: IP20 powder-coated steel with castor wheels

Technical Specifications

Product Overview

This 40kVA dry type isolation transformer steps a three-phase 380 V feed down to the single-phase 220 V or 200 V supply that sensitive equipment runs on. Primary and secondary are electrically separate, so the load is fed by induction across the core rather than by a shared conductor, and the secondary cannot carry the building's ground noise into the equipment. Because the windings are air-cooled rather than oil-immersed, the unit can be installed directly inside a plant room, production hall or hospital technical area, with no bunding, oil sampling or fire-rated enclosure to arrange around it. It is built for continuous duty, expected to stay energised for years at a time rather than switched in and out.



Isolation Principle

The shield has one job: give high-frequency noise a shorter path to earth than the secondary circuit. Switching harmonics from variable-frequency drives and UPS rectifiers, and transients from contactors and welding sets, ride on the primary winding and try to couple across to the load; bonded to earth through a drain wire, the shield intercepts that energy first. It also breaks the loop that would otherwise run from a machine chassis, through the building earth and back to the supply — the path behind erratic servo behaviour, artefacts on scanning equipment and drifting readings on analysers. Output voltage settles again within about a second after a step of up to 10 V on the input, so the load keeps seeing a steady sine wave.


Applications

CNC and precision machining — servo drives, spindle controllers and machine controls run on a 220 V supply that no longer shares a reference with welders, compressors and other drives on the same distribution board.
Hospitals and data halls — imaging suites, diagnostic rooms and rack rows fed from the building's three-phase bus; a medical data center transformer of this class keeps that equipment on a clean, isolated single-phase supply.
Semiconductor and electronics production — fabrication lines, SMT equipment and test benches where common-mode noise turns into measurement drift, false rejects and repeat calibration work.
Laboratory and metrology instruments — calibration benches, spectrometers and analysers that expect a quiet, well-referenced supply rather than a shared building circuit.
Automation and control cabinets — PLC, HMI and drive panels on the shop floor, where one isolated feed protects several cabinets at once.


Technical Support & Model Matching

Sizing power protection correctly matters more than picking the biggest unit. Our engineering team reviews your load profile, phase configuration and site conditions, then helps you match the right double-conversion UPS, voltage stabilizer or isolation transformer from our range. We assist with wiring and installation guidance, commissioning checks and fault troubleshooting, and stay reachable by email, phone or WhatsApp for questions after delivery. Installation notes, service conditions and maintenance guidance accompany each unit so your team can run it confidently.

Working Principle

An isolation transformer transfers AC energy from primary to secondary exclusively through electromagnetic induction — with no direct electrical connection. The electrostatic shield (Faraday shield) between windings diverts high-frequency common-mode noise and transient surges directly to ground, preventing them from coupling into the secondary circuit.

Installation & Wiring

Select cables and lugs of appropriate cross-section. Maintain adequate clearance on all sides for heat dissipation and maintenance access. Proper grounding is critical — connect chassis ground (PE) and electrostatic shield drain wire to a reliable earth ground. For circuits with zero-sequence current or significant imbalance, neutral conductor cross-section should equal or approach phase conductors. Before wiring, verify no short circuit and insulation resistance ≥100MΩ.

WARNING: Never reverse input/output connections. Never swap phase and neutral. All wiring must be performed with power fully de-energised.

Service Conditions

Indoor use, −5°C to +40°C. Relative humidity <93% (no condensation). Altitude <1000m. Supply voltage approximately sinusoidal (THD ≤5%), three-phase approximately symmetrical. Transient peak grid voltage U P-P ≤2000V. Store in dry, ventilated area, −20°C to +40°C, RH ≤80%.

Daily Maintenance

Dry-type isolation transformers are virtually maintenance-free under normal conditions. In dusty environments, blow out dust from windings and terminals with compressed air (≤2 atm). Check fans, winding insulation for cracks or carbonisation, terminal tightness and grounding integrity (ground resistance ≤4Ω). Record all maintenance activities.

Contact us today for a quote or technical datasheet.
WeChat / WhatsApp: +86 13360479957
Website: www.feixiangdapower.com
Email: snow@feixiangdapower.com

FAQ

Q1. How is this different from an autotransformer?
An autotransformer uses one winding, so the primary and secondary stay electrically connected and the output still carries incoming ground noise. On this 40kVA dry type isolation transformer the windings are physically separate and energy crosses only through the magnetic circuit, which breaks the ground loop and holds transient energy away from the connected equipment.

Q2. Can the input and output voltages be customised?
Yes. As an isolation transformer manufacturer we wind to the ratio your site needs — common three-phase inputs include 208 V, 240 V, 380 V, 400 V, 415 V, 480 V, 600 V and 660 V, with single-phase outputs from 100 V to 347 V. Tell us your supply voltage, load voltage and preferred connection group, and we build to that specification.

Q3. How do I choose the right capacity?
Sizing starts with the total connected load, how much of it runs at once, and the starting surge from any motor or drive. The SGG range runs from 5 kVA to 100 kVA, so send us the load list and we will confirm the rating that fits rather than leaving you with capacity you never use. Units are built and tested in our 3 phase transformer factory before dispatch.

Q4. Can this transformer serve medical and data center loads?
Yes — a medical data center transformer of this type is standard equipment in imaging rooms, diagnostic areas and server halls, where single-phase equipment is fed from a three-phase distribution board and needs its own isolated reference. The 380 V in / 220 V out pairing covers the most common arrangement, and other ratios are available where your site differs.

Q5. What maintenance does it need?
Very little in normal service. In dusty areas, blow the windings and terminals out with compressed air at no more than 2 atm; check the cooling fan, look for cracks or carbonisation in the insulation, retighten the terminals and confirm the grounding is intact at 4 Ω or better. Record every inspection so a trend shows up before it becomes a fault.

Q6. Does it come as a bare unit or in a cabinet?
Both are available. As a specialist isolation transformer manufacturer we supply either format: the enclosed version ships in a powder-coated steel cabinet on swivel castors with locking brakes, while the bare version is supplied without a cabinet for mounting inside your own panel or switchroom. Bare units measure 480 × 380 × 420 mm and weigh 160 kg, and the chassis model measures 700 × 500 × 650 mm and weighs 200 kg.