Product Overview

The HET 20kVA exciter transformer is a heavy-duty, single-phase unit designed for precision high-voltage testing with three selectable outputs (20kV/15kV/10kV). Engineered with ONAN cooling and advanced electrostatic shielding, it complies with IEC 60076-11 for dielectric testing in power utilities and industrial labs.

Electrical Specifications

Protection Systems

1. Overvoltage Protection

• Piezoresistors on all HV outputs

• Zinc oxide arresters (IEC 60099-4) on terminals

• Ground-connected via 20kA surge arresters

2. Corona & Insulation Control

• 20kV corona-free HV bushings

• Isovolumetric capacitance cores for stable voltage gradient

• Dual corona rings per bushing

Mechanical Design

Enclosure Features

• 12-gauge steel housing with corrosion-resistant coating

• Wheel-mounted (4× heavy-duty casters)

• Shell-type oil tank with 50L conservator

Terminal Configuration

• LV terminals: Porcelain bushings (380V input)

• HV terminals: Fiberglass-reinforced bushings

• Voltage-graded insulation for all taps

Winding Technology

Advanced Insulation

• Cylinder-type winding with balanced capacitance distribution

• Electrostatic shields between HV/LV windings

• Inter-turn insulation (0.75mm Nomex® layers)

Dielectric Performance

• Impulse withstand: 125kV (1.2/50μs wave)

• Power frequency withstand: 25kV/min

• Partial discharge <10pC per IEC 60270

Installation & Maintenance

Commissioning Requirements

• Minimum 1.2m clearance from grounded objects

• Oil dielectric strength ≥50kV pre-energization

• Initial insulation resistance ≥10,000MΩ

Service Schedule

• Bi-annual oil analysis (BDV, moisture content)

• Bushing torque check every 12 months

• Winding resistance test every 5,000 operating hours

Typical Applications

• Power transformer routine testing

• GIS (Gas Insulated Switchgear) commissioning

• Rotating machine insulation testing

• High-voltage cable factory acceptance tests