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Variable Transformers
6 Series · 66 Models
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Variable Transformers Overview
Variable auto-transformers deliver continuous, stepless AC voltage adjustment through a carbon brush moving over a toroidal winding. QDTB units adjust 0-250 V single-phase (TDGC2) and 0-430 V three-phase (TSGC2) from 0.5 kVA to 30 kVA, with smooth, precise output. Typical uses include laboratory testing, electric furnace temperature control, stage lighting dimming, and instrument calibration. DTY series covers special applications and TSZ2 premium requirements.
Available Series
TDGC2 Series
The TDGC2 series single-phase contact voltage regulators provide continuously adjustable output voltage from 0 to 250V. Used extensively in laboratories, testing, and industrial applications.
TSGC2 Series
The TSGC2 series three-phase contact voltage regulators provide continuously adjustable output voltage from 0 to 430V for three-phase power applications.
TSJA-TDJA Series
The TSJA (three-phase) and TDJA (single-phase) series oil-immersed variable transformers provide high-capacity continuously adjustable voltage output for heavy-duty industrial applications.
DTY Series
The DTY series intelligent contact voltage regulators feature digital display and microprocessor control for precise voltage adjustment with enhanced safety features.
TSZ2 Series
The TSZ2 series three-phase magnetic contact voltage regulators use electromagnetic principle for smooth voltage regulation with high reliability and long service life.
SCR Power Regulators Series
SCR (thyristor) power regulators provide stepless power control for resistive heating loads by phase-angle or zero-cross firing of thyristors. Rated 10–2000 A for single-phase and three-phase loads, they regulate power to electric heaters, furnaces and drying ovens with fast response and high efficiency.
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Application Scenarios
Laboratory Testing
Provides adjustable AC voltage for testing devices across their rated input range.
Electric Furnace Control
Stepless temperature control for resistance furnaces and heating elements.
Stage Lighting
Smooth dimming of incandescent stage and studio lighting.
Instrument Calibration
Precise variable supply for calibrating meters, sensors and relays.
Motor Speed Control
Voltage adjustment for small single-phase and three-phase motor speed regulation.
Education & Training
Safe, adjustable AC source for teaching labs and demonstrations.
Technical Advantages
Stepless Adjustment
Continuous 0-250V (single-phase) or 0-430V (three-phase) output with no steps.
Smooth Carbon-Brush Contact
Carbon brush on a toroidal winding delivers precise, wear-resistant adjustment.
Toroidal Winding
Uniform flux distribution for low noise and compact size.
Wide Capacity Range
From 0.5 kVA lab units to 30 kVA industrial regulators.
FAQ - Variable Transformers
What is the difference between a variable transformer and a voltage regulator?
Can it run at full load continuously?
Should I choose single-phase or three-phase?
What is the minimum order quantity (MOQ) for Variable Transformers?
What is the delivery time for Variable Transformers?
Which standards and certifications do your Variable Transformers comply with?
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Variable Auto-Transformer vs SCR Regulator vs Servo-Motor AVR: How to Choose
| Variable Auto-Transformer (TDGC2) | SCR Power Regulator | Servo-Motor AVR | |
|---|---|---|---|
| Adjustment | Manual dial, stepless, set by the operator | Electronic phase-angle control from a command signal | Automatic motor drive that follows the mains |
| Control source | Hand set, with no feedback loop | Analogue or digital command from a controller | Internal feedback holding a fixed output |
| Output range | Zero up to the full winding voltage | Zero to full voltage, in fine electronic steps | A narrow trim around the nominal voltage |
| Load type | Test benches, furnaces, lighting and calibration work | Heaters and resistive loads under closed-loop control | Equipment that must stay at nominal voltage |
| Distortion | None added, the waveform passes through | Switching adds harmonic content | None added |
| Wear parts | Carbon brush and track need periodic checks | No moving parts | Brush and servo motor |
| Typical application | Laboratories and training | Furnace and oven temperature control | Mains stabilisation for sensitive loads |
Where QDTB® Variable Transformers Are Specified
Variable auto-transformers are specified where an engineer has to dial a voltage rather than accept one: laboratory testing, instrument calibration and education benches, where the output is swept from zero to the full winding voltage and the waveform must stay clean. The stepless carbon-brush contact is what makes a slow, continuous sweep possible without tap steps.
Electric furnace and oven control uses the three-phase units to set the heating voltage directly, and stage-lighting dimming uses the same principle on a smaller scale. In both cases the load is resistive and the operator wants a predictable voltage rather than a closed-loop controller.
Motor speed control on legacy equipment is another field use, where the variable transformer sets the voltage applied to the motor and the operator accepts the reduced torque that comes with it. Where full torque at low speed is needed, a drive is the correct device and the variable transformer is not.
Units cover 0.5 kVA to 30 kVA in the standard single-phase and three-phase lines, extending to 500 kVA across the range. Keep the brush surface clean and derate slightly for continuous duty at full rating.
Frequently Asked Questions
What is the difference between a variable transformer and a voltage regulator?
A variable transformer is manually adjusted to set an output voltage. A voltage regulator automatically maintains output within a tolerance as input varies.
Can it run at full load continuously?
Yes, within the rated capacity. Keep the brush surface clean and derate slightly for long continuous runs.
Should I choose single-phase or three-phase?
Use TDGC2 (single-phase) for single loads, TSGC2 (three-phase) for balanced three-phase systems.
What is the minimum order quantity (MOQ) for Variable Transformers?
One unit for standard products. Custom-designed equipment is quoted on specifications — send your parameters or drawings and our sales team will confirm the MOQ for your configuration.
What is the delivery time for Variable Transformers?
Standard units are delivered in 30-45 days. Custom or large-capacity units follow a project-specific schedule confirmed at quotation. Rush orders can be accommodated for urgent projects.
Which standards and certifications do your Variable Transformers comply with?
Each unit is designed to the IEC, IEEE or GB standard your project specifies. All QDTB® equipment is ISO 9001 certified and CE marked, and the company operates ISO 9001, ISO 14001 and ISO 45001 management systems.