High Impedance Transformers

Osborne high impedance transformers are used to step-up, step-down and isolate voltages in single phase and three phase circuits. A properly designed high impedance transformer can be used an an equivalent to an isolation transformer connected in series with an inductor. The high impedance characteristic may be employed as a current limiting feature in both the primary and secondary circuity.


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High Impedance Transformer Design Options Table

Spec Range Available
Primary Voltage: 1 – 10,000 Volts
Secondary Voltage: 0.1 – 20,000 Volts
Secondary Current: 0.001 – 10,000 Amps
Capacity: 0.000001 VA – 250 KVA
Frequency: 10 HZ – 2.0 Mega-Hertz
Phase: Single – Multiple
Electrostatic Shielding: Single to Multiple Shields
Terminals: Wire Leads – Finger Safe Terminals
Enclosures: Open Core & Coil – Hazardous Environment
Dielectric Strength Testing: 50 Volts DC – 50,000 Volts AC
Agency Approvals: UL, CSA, CE and/or TUV

Featured Osborne High Impedance Transformers

High Impedance Transformers for Dielectric Strength Testing

The high impedance transformers pictured above were designed for testing the dielectric strength of an electrical insulation system. The test involves thermal aging in accordance with the IEEE standard procedure for “Evaluation of Systems of Insulating Materials for Random Wound AC Rotating Electric Machinery.”

High Impedance Transformers Limit Currents With Uncommon Loads

Osborne has also developed high impedance transformers to limit inrush currents in machines that operate uncommon loads. One example of an uncommon load is a tungsten filament. Tungsten filaments have extremely low resistance when in a low temperature state. As the filaments heat up, the supply current falls and voltage increases until both current and voltage stabilize within the machine’s normal operating range. A high impedance supply transformer will effectively reduce the magnitude of inrush current spikes; spikes that might otherwise cause unnecessary damage or premature aging to adjacent circuitry.

Another example of how high impedance transformers offer current limiting with uncommon loads can be seen in capacitor charging banks. Some capacitor charging banks depend on the current limiting benefits of high impedance supply transformers. Capacitor bank circuits often use sensitive semiconductor rectifier assemblies which can be damaged from exposure to excessive inrush current spikes. A high impedance supply transformer will limit currents at times when capacitors are discharged, thereby protecting the rectifier assemblies and other components. This current limiting does not interfere with the normal capacitor charging, and the capacitors will charge up to the no-load peak secondary voltage when the charging current nears zero.

What Are Osborne’s High Impedance Transformer Design Options?

The “Design Options Table” above outlines the types of features typically available for Osborne’s High Impedance Transformers. We share these options to help you determine if Osborne’s capabilities are a good fit for your project.

If you’re looking to develop a custom high impedance transformer and it fits in the ranges of Osborne’s high impedance transformer design options table, there’s a great chance that we can make your project a success. Call Osborne today at 800-229-9410.

Why Choose Osborne?

Premium high impedance transformers are ideal for select applications. Does your project demand exceptional design service and high performance? If so, please consider our Design Options page for details about the performance benefits of application specific engineering. Next we encourage you to visit our Partners page for a clear idea of Osborne’s unique collaborative development approach.