Representative imageConstant Voltage Transformers
A Constant Voltage Transformer (CVT), also called a ferroresonant transformer, holds its output voltage steady despite wide swings in input voltage, with no moving parts or electronics.
Overview
A Constant Voltage Transformer (CVT), also called a ferroresonant transformer, holds its output voltage steady despite wide swings in input voltage, with no moving parts or electronics. It works by deliberately driving a section of the magnetic core into saturation; a tertiary winding paired with a capacitor forms a resonant ('tank') circuit that locks the output near a fixed level. Because of this it provides fast, robust line and load regulation (typically within a few percent), inherent galvanic isolation, a clean near-sinusoidal output, spike/noise attenuation and ride-through of brief input dropouts — making it a rugged choice for protecting sensitive or critical loads where a maintenance-free, electronics-free stabilizer is preferred. The trade-offs a buyer accepts are lower efficiency, sensitivity to frequency and a fixed VA rating. CVTs are best suited to fixed, well-defined loads such as instrumentation, control systems and process equipment.
Specifications
| Output rating | typically 100 VA up to ~10 kVA (single units; larger by paralleling) |
|---|---|
| Output voltage regulation | within ~1-3% for wide input variation |
| Input voltage window | commonly ±15% to ±20% (or wider) of nominal |
| Phases | single-phase (three-phase via banked units) |
| Frequency | 50 Hz or 60 Hz (frequency-sensitive — must be specified) |
| Output waveform | near-sinusoidal; harmonic/THD figure per design |
| Isolation | galvanic primary-to-secondary isolation |
| Response time | typically 1-2 cycles |
| Efficiency | ~70-90% (lower than conventional transformers) |
| Short-circuit / overload | inherently current-limiting |
| Cooling/enclosure and IP rating per application | |
Applications
- Voltage stabilization for sensitive electronic and control loads
- Instrumentation, lab and process equipment
- Industrial automation / PLC and control-panel supplies
- Medical and telecom equipment
- Protection against sags, spikes and line noise
Frequently asked questions
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