Ozone Generator and DBD Transformer Design: Insulation First

Ozone Transformers Run Where Insulation Fails First

An ozone generator uses a dielectric barrier discharge (DBD) cell driven at 10–30 kHz and several kilovolts, with a transformer that must deliver a high-voltage, high-frequency waveform into a strongly capacitive load. Failures in this application almost never come from the magnetic design; they come from partial discharge, corona at the winding ends, and thermal runaway in a sealed enclosure.

This note covers what makes an ozone or DBD transformer different, and the specification points buyers need.

Electrical Character

Parameter	Typical value	Design impact
Drive frequency	10–30 kHz	Ferrite core; Litz or foil windings
Output voltage	3–15 kV peak	Reinforced insulation, PD-free construction
Load	Capacitive DBD cell, 100 pF to a few nF	Resonant operation, high circulating current
Duty	Continuous in water treatment; pulsed in some industrial units	Thermal design and potting
Cooling	Often air or water cooled cell; transformer in a sealed box	Hotspot control

The load is capacitive, so the transformer current is dominated by the cell’s reactance rather than by real power. A design that sizes the secondary for output power alone will overheat, because the circulating current can be several times higher.

Insulation Is the Design

At kilovolt output, three things decide life: the barrier between primary and secondary, the potential grading at the winding ends, and the absence of voids. Practical construction: multiple layers of high-temperature tape or a segmented bobbin, vacuum pressure impregnation to remove voids, and physical separation of the highest-voltage end from the core.

Corona at the ends of a high-voltage winding erodes insulation steadily and shows up as a slow IR decline. Potting the ends, or using a graded winding with the last layers spaced further apart, extends life substantially. This is why high-voltage transformers in this class are often fully encapsulated.

Partial Discharge Specification

For a DBD transformer, partial discharge inception voltage should be above the peak operating voltage with margin — commonly at least 1.2–1.5×. The test is done at the operating frequency or at a lower frequency with an equivalent waveform, and the result is reported in picocoulombs. A supplier who only reports hipot results has not tested the failure mode that matters.

Thermal and Magnetic Details

Core: MnZn ferrite, often with a gap to stabilize inductance against the capacitive load.
Winding: Litz for the primary at 20 kHz and above; the secondary may use layer winding with tape between layers for voltage grading.
Resonance: the transformer’s leakage inductance frequently forms part of the resonant tank, so leakage inductance must be specified with a tolerance, not left to construction.
Thermal: encapsulated construction raises thermal resistance; specify the hotspot and verify with a thermocouple inside the potting during type test.

What to Specify

Drive frequency and waveform, output voltage and current, and the cell capacitance.
Required leakage inductance, if the transformer is part of the resonant tank.
PD inception requirement and the test method.
Insulation system, encapsulation, and the maximum hotspot.
Cooling method and enclosure ambient.
Life requirement and the expected duty cycle.