AltraVolt – Servo Voltage Stabilizer & Isolation Transformer Manufacturer

Indian Standards (BIS) Governing Voltage Stabilizers

AltraVolt designs and tests its single-phase servo stabilizers against the relevant Bureau of Indian Standards (BIS) specifications. Here's a detailed breakdown of what each standard covers.

IS 9815 (Part 1) — Servo-Motor Operated Automatic Line Voltage Correctors: General Requirements

This is the foundational standard for servo-type stabilizers in India (last major revision 1994, Transformers Sectional Committee, ETD 16, Bureau of Indian Standards). It defines what qualifies as a "servo-motor operated automatic line voltage corrector," covering construction, terminology, rated input/output voltage windows, duty classification, marking and nameplate requirements, and general safety construction norms (enclosure, terminal access, earthing provision). It distinguishes servo-driven correctors from the simpler relay/tap-changing "buck-boost" correctors covered separately under IS 8448.

IS 9815 (Part 2) — Performance Requirements

Part 2 lays out the actual performance benchmarks a servo stabilizer must meet: regulation accuracy (typically required within ±1% of nominal output), correction/response speed, no-load and full-load losses, temperature-rise limits during continuous duty, dielectric (high-voltage withstand) test requirements, and routine/type test procedures (voltage regulation test, efficiency test, temperature-rise test, insulation resistance test, and short-circuit withstand where applicable). Compliance with Part 2 is what manufacturers reference when they print "Conforms to IS 9815" on a stabilizer's rating plate.

IS 8448:1989 — Automatic Line Voltage Correctors (Buck-Boost / Relay Type)

A related but distinct standard covering the simpler relay-driven or tap-changing automatic voltage correctors typically used with refrigerators, TVs, and air conditioners, generally rated for a 210–250 V input/output band. Servo stabilizers are the more precise, continuously-variable cousin of the devices this standard addresses — useful to know when comparing a basic "voltage stabilizer" sold for home appliances against a true servo-controlled unit.

IS 2026 (Parts 1–8) — Power Transformers

Because every servo stabilizer is built around a buck-boost transformer (and, in oil-cooled designs, an oil-filled transformer tank), the transformer windings inside the stabilizer are designed and tested in line with IS 2026: Part 1 (general requirements), Part 2 (temperature rise limits), Part 3 (insulation levels, dielectric tests, and clearances in air), Part 5 (short-circuit withstand ability), and Part 8 (application guide). This is why reputable stabilizer manufacturers will quote IS 2026 alongside IS 9815 on their datasheets.

IS 335 — Specification for New Insulating Oils

For oil-cooled servo stabilizers (common above ~15–25 kVA), the transformer oil used for cooling and insulation must meet IS 335, which governs dielectric strength, flash point, viscosity, and moisture content of new mineral insulating oil before it's filled into the tank.

BIS / ISI Certification & CE Marking

Beyond the technical IS specifications, manufacturers may carry BIS/ISI certification marks confirming third-party verification against these standards, and where stabilizers are exported, CE marking (Europe) or equivalent IEC 60076-aligned documentation (for oil-cooled units, the international parallel to IS 2026) is often added to satisfy overseas buyers.

Note on accuracy: BIS standards are periodically revised, reaffirmed, or withdrawn. When quoting IS numbers on datasheets or marketing material, it's worth double-checking the current status on the official BIS website or the latest edition of the standard, since some referenced parts (for example certain dry-type transformer specifications) have been superseded over the years.

Single-Phase Servo Voltage Stabilizer

Technical Specifications