Overview
EN ISO 10656:2021 (identical to ISO 10656:2016, corrected) specifies additional requirements for single‑phase integrated transformers for welding guns used in AC resistance welding. It is intended to be used in conjunction with ISO 5826 (general transformer specifications) and amends/extends those requirements for transformers built into welding tongs/guns. The document is endorsed by CEN as EN ISO 10656:2021.
Key topics and technical requirements
- Scope & usage
- Adds specific requirements to ISO 5826 for transformers integrated into welding guns used in resistance welding (AC).
- Dimensions & types
- Defines transformer types (notably type H and type J) with associated dimensions and electrical characteristics (separate tables for 50 Hz and 60 Hz).
- Includes detailed mounting and connection layouts (figures for output areas and mounting holes).
- Cooling & duty
- Specified cooling water flow rate: Q = 4 l/min.
- Suitable for duty cycles up to 20% (see Annex A).
- Grounding & safety
- Secondary coil centre point must be connected to the transformer case via a removable link (grounding provision).
- Thermal protection: primary and secondary windings require thermoswitches. Wiring colour coding: light blue for primary thermoswitch, black for secondary.
- Measurements & sensing
- Transformers must include an output current sensing coil as required by ISO 5826.
- Marking & identification
- Voltage and earth connections must be clearly marked: U, V and the IEC symbol 60417‑5019.
- Rating plate follows ISO 5826 with box 4 referencing ISO 10656:2016.
- Exterior finish colours are standardized according to AC no‑load voltage for both 50 Hz and 60 Hz units.
- Testing
- Additional type tests are specified: mechanical strength (tensile loading on mounting holes) and tests for dynamic behaviour of output terminals and thermal performance.
- Designation example
- Example format: ISO 10656:2016 – J – 7,1 – 5,4 – 400 – TM (type, voltages, supply, thermoswitch and sensing coil indicators).
Applications and who uses this standard
- Manufacturers of resistance welding equipment and integrated welding gun transformers (design, production, QA).
- OEMs and system integrators specifying transformers for automated welding guns.
- Test laboratories and conformity assessors conducting type and thermal tests.
- Procurement and maintenance teams ensuring interoperability, safety, correct mounting, cooling and identification.
- Helps ensure safety, reliability, interchangeability and clear marking in resistance welding installations.
Related standards
- ISO 5826 - General specifications for all resistance welding transformers (primary normative reference).
- IEC 60417‑DB - Graphical symbols for equipment marking (IEC 60417‑5019 referenced).
Keywords: EN ISO 10656:2021, integrated transformers for welding guns, resistance welding, transformer specifications, ISO 5826, welding equipment, thermoswitch, output current sensing.
