This Standard defines and specifies the characteristics of single-phase resistance weldingequipment. It includes the information required on the equipment nameplate and specifies the testmethods to be used to verify the compliance of the equipment with the requirements of this Standard.NOTE: Appendix A gives i nformati on on t hermal ti me constants.It is applicable to single-phase resistance welding equipment, including all types of complete portableequipment, for use under the following conditions:(a) Altitude The altitude shall not exceed 1000 m.(b) Cooling medium temperature For water-cooled equipment, the temperature of the cooling watershall not exceed 30°C at the inlet of the equipment and, in the case of air-cooled equipment, noneof the following limits shall be exceeded:(i) Maximum ambient air temperature: 40°C.(ii) Daily average ambient air temperature: 30°C.(iii) Yearly average ambient air temperature: 20°C.(c) Cooling water pressure The pressure of the cooling water shall not be less than that which isnecessary to supply the rated flow of cooling water.This Standard does not apply to transformers sold separately or to capacitor discharge or rectifierequipment.For a given voltage and frequency the characteristics of the equipment are calculated, constructed andtested, as a function of the following operational modes:(i) Intermittent operation at a duty cycle (see Clause 1.3.4) of 50%, the values of current and powerbeing termed nominal or rated.(ii) Continuous operation, the values of current and power being termed continuous.All voltages and currents shall be expressed as r.m.s. values.