Technical questions answered
Twelve questions a buyer or specifying engineer actually asks. Each answer either cites the standard it comes from, or names the Jayess certificate behind it — and where the honest answer is that something is not published, it says so rather than filling the gap.
Transformers
- What is a control transformer?
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A control transformer supplies the control circuit of a machine or panel, stepping the incoming supply down to the voltage the contactors, relays and instruments need — commonly 110 V or 24 V from a 415 V line.
It is sized for the inrush of the largest contactor coil it has to pull in, not simply for the steady-state load. A transformer rated only for holding current will drop enough voltage on energisation that the contactor never latches.
SourceIEC 61558-2-2, the standard for control transformers
Not publishedRatings are set against your control schematic rather than published as a range.
- What is a distribution transformer?
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A distribution transformer takes a medium-voltage supply and steps it down to the low voltage a site actually distributes at — in India typically 11 kV to 433 V.
Selection turns on four things beyond the rating: the vector group, which fixes the phase relationship between windings; percentage impedance, which sets both fault level and voltage regulation; the cooling class; and the loss figures, which decide the running cost over the transformer’s life rather than its purchase price.
SourceIS 1180 and IS 2026 for distribution transformers
Not publishedNo specific rating is published as a maximum. The rating is confirmed against your load and fault-level data at enquiry.
- Where are control transformers used?
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Anywhere a machine has a control circuit at a lower voltage than its power circuit: machine tools, packaging and process lines, switchgear panels, and the control section of an MCC.
They are also used to isolate the control circuit from the supply, so an earth fault in field wiring does not put line voltage on a pushbutton or a limit switch.
SourceIEC 61558-2-2
- What information is required to size a distribution transformer?
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Connected load and expected maximum demand; primary and secondary voltage; vector group; percentage impedance, or the fault level you need to design to; cooling class; whether it is indoor or outdoor; and the ambient conditions at site.
If the load includes drives or other non-linear equipment, say so — harmonic loading affects derating, and a transformer sized on nameplate kVA alone can run hot on a load that never exceeds it on paper.
SourceIS 1180; IEC 60076 for loading and temperature rise
Voltage regulation
- What is a servo voltage stabiliser?
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A servo voltage stabiliser holds output voltage steady while the incoming supply swings. A motor-driven wiper moves across a variable transformer, and a buck-boost winding adds or subtracts the difference.
It corrects magnitude, and only magnitude. It is not a UPS and does not ride through an outage; it does not correct power factor; and because correction is mechanical it responds in a fraction of a second rather than instantly. For equipment that cannot tolerate any break, a stabiliser and a UPS do different jobs.
SourceGeneral electrical engineering practice; construction as described in IS 9815 for automatic voltage stabilisers
Not publishedCorrection range and response time are set per order and are not published.
Panels and switchgear
- What is the difference between a PCC and an MCC panel?
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A PCC — power control centre — is the incoming and distribution board. It receives the supply, meters and protects it, and feeds outgoing circuits, usually through air circuit breakers and moulded-case breakers.
An MCC — motor control centre — is downstream of it and exists to start, stop and protect motors. Its modules carry starters: contactors, overload relays, and increasingly variable frequency drives or soft starters.
Both are low-voltage switchgear assemblies covered by the same standard, and both are specified by their Form of separation, short-circuit withstand and ingress protection rating rather than by the name on the front.
SourceIS/IEC 61439-2, low-voltage switchgear and controlgear assemblies
- Power control centres built to IS/IEC 61439-2IS/IEC 61439-2Referenced standard
Not publishedForm of separation and short-circuit withstand are not published for any Jayess panel — no type-test evidence is on file, and a Form designation stated without one would be a claim we cannot support. Both are confirmed against your drawing at enquiry.
- What is an APFC panel and when is it needed?
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An APFC — automatic power factor correction — panel switches capacitor banks in and out to hold power factor near unity as the load varies. A controller measures reactive demand and brings steps in or out to match it.
It is worth having where an inductive load fluctuates and the tariff penalises poor power factor, or where correcting reactive current releases capacity in cables and transformers you already own. A fixed capacitor bank is cheaper but overcorrects at light load, which brings its own problems.
Where the load includes drives or other non-linear equipment, harmonics matter: capacitors and system inductance can resonate, and detuned reactors are the usual answer.
SourceIS/IEC 61439-2 for the assembly; IEEE 519 for harmonic limits
- Power control centres built to IS/IEC 61439-2IS/IEC 61439-2Referenced standard
Not publishedStep sizes, controller make and whether detuned reactors are included are decided per order.
- What information is required to quote a control panel?
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A single-line diagram or schematic; the incoming supply and required fault level; the outgoing feeder schedule with ratings; preferred switchgear makes; the Form of separation and ingress protection rating you need; and whether the panel is indoor, outdoor or in a corrosive or dusty environment.
Where a drawing does not exist yet, the load list and the duty are enough to begin: the schematic is part of the engineering work rather than a prerequisite for it.
SourceIS/IEC 61439-2
- Power control centres built to IS/IEC 61439-2IS/IEC 61439-2Referenced standard
Testing, standards and licensing
- How are transformers and panels tested before dispatch?
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Routine tests at the works establish that what was built matches what was designed: winding resistance, ratio and polarity, insulation resistance, and applied and induced overvoltage withstand. Panels are additionally checked for wiring continuity against the schematic and for correct operation of protection and interlocks.
Jayess tests at its own works testing station before dispatch, and the quality management system covering the Faridabad works is certified to ISO 9001:2015.
SourceIS 2026 for transformer routine tests; IS/IEC 61439-2 for assembly verification
- Electrical testing station at the works, including a 5 kV high-voltage breakdown testerHVTD-5Evidences that the equipment exists and is in use. No calibration certificate, test report or type test is held, and none is implied.
- ISO 9001:2015 quality management certificateE20250830652Royal Assessments Pvt. Ltd., accredited through EGACOpen document
Not publishedType tests and third-party test certificates are a different thing from routine tests, and none is on file. No type-test evidence is claimed anywhere on this site.
Distribution transformersControl transformers Manufacturing & worksTesting & commissioning
- Which standards does Jayess build to?
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Low-voltage assemblies are built to IS/IEC 61439-2. The quality management system at the Faridabad works is certified to ISO 9001:2015 under certificate E20250830652, issued by Royal Assessments Pvt. Ltd. and accredited through EGAC, a member of the International Accreditation Forum. That certificate is subject to surveillance audits, so its current status is worth checking at iafcertsearch.org.
That certificate is independently verifiable at iafcertsearch.org. It certifies the management system, not any individual product.
SourceIS/IEC 61439-2; ISO 9001:2015
- Power control centres built to IS/IEC 61439-2IS/IEC 61439-2Referenced standard
- ISO 9001:2015 quality management certificateE20250830652Royal Assessments Pvt. Ltd., accredited through EGACOpen document
Not publishedA management-system certificate is not a product approval and is not presented as one. No product type approval is claimed.
- Is Jayess & Co. certified and licensed?
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Yes, and both can be checked. The ISO 9001:2015 certificate covering the Faridabad works is E20250830652, issued by Royal Assessments Pvt. Ltd. and accredited through EGAC. It runs to 13 August 2028, subject to surveillance audits the certificate requires on or before 13 August 2026 and 13 August 2027 — so check its current status at iafcertsearch.org rather than taking the end date as confirmation. The electrical contractor licence 50590000009690 is issued by the Labour Department, Government of NCT of Delhi, and valid to 10 August 2050.
The licence requires installation work to be carried out under the direct supervision of a Certificate of Competency Class-I holder.
SourceISO 9001:2015; Government of NCT of Delhi electrical licensing
- ISO 9001:2015 quality management certificateE20250830652Royal Assessments Pvt. Ltd., accredited through EGACOpen document
- Electrical contractor licence — Government of NCT of Delhi50590000009690Labour Department, Government of NCT of DelhiOpen document
- Licence requires all installation work to be carried out under the direct supervision of a holder of a Certificate of Competency Class-I (Electrical Supervisor), and by a holder of Class-II (Electrician)50590000009690Labour Department, Government of NCT of DelhiOpen document
Not publishedA certificate of compliance, ICM-CE-25032228 from ICMBV Limited, is on file and valid to 13 August 2028. It is not an EU Declaration of Conformity, names no Notified Body, and cites directives that have been repealed — so no claim of current EU conformity is made from it anywhere on this site.
- Does Jayess install and commission on site?
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Yes. Installation and commissioning are separate capabilities with their own scope, carried out under the Delhi electrical contractor licence and its Class-I supervision requirement.
Annual maintenance and servicing of previously supplied equipment is also offered as its own capability rather than bundled into supply.
SourceGovernment of NCT of Delhi electrical contractor licence 50590000009690
- Electrical contractor licence — Government of NCT of Delhi50590000009690Labour Department, Government of NCT of DelhiOpen document
- Licence requires all installation work to be carried out under the direct supervision of a holder of a Certificate of Competency Class-I (Electrical Supervisor), and by a holder of Class-II (Electrician)50590000009690Labour Department, Government of NCT of DelhiOpen document
Not publishedNo named site, client or installed project is published. No project record has been supplied and no permission to name a client is held.
A question not answered here is usually one that needs your drawing or load data before it can be answered honestly. Send it through and it reaches an engineer rather than a mailbox.
Send the requirement
Send the rating, the single line diagram and the site. That is enough for a firm quotation — an enquiry without them gets a phone call asking for them.