Variac Controlled AC Power Supply Manufacturer & Exporter in India

A variac — properly a variable autotransformer — is a single continuous winding on a toroidal core, with a short arc of that winding left bare so a carbon brush can ride directly on the copper. Mains is applied across the full winding; the output is taken between one end of the winding and the brush. Rotating the dial moves the brush along the exposed track, changing how many turns sit between the two output terminals, and therefore changing the output voltage.

The critical consequence is what does not happen. Because the output is a transformer tap that simply moves, the supply never chops the waveform. Compare that with a phase-angle or thyristor-based voltage controller, which reduces the RMS output by switching off part of each half-cycle and hands the load a distorted waveform full of harmonics. A motor, a transformer or an inductive test article behaves very differently on those two supplies — which is why variacs remain standard equipment on motor and appliance test benches even where programmable sources are available.

Because it is an autotransformer rather than an isolating transformer, the primary and secondary share the winding, so losses and heat rise are lower and efficiency is high — but there is no galvanic isolation between input and output. Where isolation is required by the test procedure, an isolation transformer is fitted ahead of the variac. Output current capacity is set by the winding cross-section and brush contact area, which is why the range is specified in amps rather than kVA.

A variac is chosen when the requirement is clean, stepless voltage variation under manual operator control — not when the requirement is programmed sequencing or frequency variation. The mapping below reflects where that distinction actually matters on the shop floor.

Buyers frequently confuse these three products because all of them "change the AC voltage". They solve different problems, and the table below is the fastest way to place an enquiry in the right category.

• Maximum load current, not kVA — variac capacity is set by winding and brush current rating, so quote the actual amps the load draws including starting inrush.
• Input supply available — 230VAC single phase or 415VAC three phase, and whether a neutral is present at the bench.
• Output voltage range required — standard 0-100% of input, or a boost-wound unit if the test procedure needs above-mains voltage.
• Isolation requirement — a variac is an autotransformer and provides no galvanic isolation. If the procedure requires it, an isolation transformer must be fitted ahead of the unit.
• Metering needed — voltage only, voltage and current, or additional power and power-factor display.
• Protection level — basic input MCB, or overload and short-circuit protection for a bench where DUT failure is routine.
• Duty cycle — occasional bench use or continuous shift operation, which changes the thermal design.
• Mounting and termination — table-top, panel-mounted or trolley, with closed terminals or socket outlets.

Standard capacities cover 10A through 100A, but the majority of installations involve at least one non-standard element. POWERTRON builds to specification: higher current ratings, three-phase ganged variac assemblies with mechanically coupled dials, boost-wound units delivering above-mains output, motorised variacs with remote or push-button drive, and non-standard input voltages for export installations.

Enclosure and metering are equally configurable — panel-mount, trolley-mounted or cabinet format, digital or analogue metering, additional kW and power-factor display, socket outlet arrangements matched to the customer's existing plug standard, and integrated isolation transformers where the test procedure demands galvanic separation. Share the load current, input supply, output range, metering requirement and mounting constraint, and the application engineering team returns a proposed configuration with an indicative timeline. Design, winding, assembly and testing all happen in-house at Thane, so custom builds carry no import lead-time penalty.