IEC 60974-12:2011 pdf free download – Arc welding equipment
The a.c. test voltage shall be of an approximate sine waveform with a peak value notexceeding 1,45 times the r.m.s. value, having a frequency of 50 Hz or 60 Hz, applied for 1 minbetween the live parts and the metal foil.
7.3.2 Additional requirements for striking and stabilizing voltage rating
For couplers for use with arc striking and stabilizing voltage, the insulation shall withstand therated peak arc striking and stabilizing voltage as rated by the manufacturer. The insulationshall withstand a high frequency voltage of pulse width 0,2 us to 8 us, a repetition frequencyof 50 Hz to 300 Hz and shall be 20 % higher than the rated peak arc striking and stabilizingvoltage as determined by the manufacturer.
Conformity shall be checked by the following test.
For couplers intended for use with arc striking and stabilizing voltage, the couplers shall besubjected to the high-frequency test voltage.The full value of the high-frequency voltage isapplied for 2 s between the electrode circuit and
a) conductive surfaces;
b) other isolated circuits.
Flashover or breakdown shall not occur.Any discharges unaccompanied by a voltage drop(corona) are disregarded.
Alternatively， for couplers intended for use with arc striking and stabilizing voltage，an a.c.test voltage of approximately sine waveform at 50 Hz or 60 Hz may be used.
7.4Protection of live parts against unintentional contact
Parts designed to carry welding current and likely to be live after disconnection shall berecessed to a depth of at least 10 % of the internal diameter of the insulation with a minimumdepth of 2 mm with respect to the insulating body.
As a consequence，insulation has to be able to withstand normal service conditions so thatthe protecting length is maintained during the life of the coupling device.
Conformity shall be checked by linear measurement and visual inspection.
8.1 Temperature rise
The temperature rise caused by the current passing through a coupling device normallycoupled and fitted with an untinned copper welding cable of maximum cross-sectional area asindicated in Table 1 shall not exceed 45 K at the hottest spot of the external surface.
Conformity shall be checked by the following test.
The coupling device is normally coupled and fitted with at least 2 m long welding cables.Thecoupling device is suspended by its welding cables from two wooden laths 1 m apart, hangingbetween the two laths in the horizontal plane about 200 mm above the ground in a draught-free area.
A continuous d.c. current equal to 75 % of the test current (equivalent to approximately 60 %duty cycle) is passed through the coupling device until the rate of the temperature rise doesnot exceed 2 K/h. During the total test time，the d.c. current shall be kept constant with atolerance of± 2 %.
8.2Resistance to hot objects
The insulation shall be capable of withstanding hot objects and the effects of a normal amountof weld spatter without being ignited or becoming unsafe.
Conformity shall be checked with a device in accordance with Figure 1.
9.4Welding cable connection
The design of the coupling device shall be such that welding cables with a cross-sectionalarea within the range as specified by the manufacturer can be replaced.The connection shallwithstand the mechanical stress of the tensile test without separation.
Conformity shall be checked by visual inspection and by the following test.
A plug，a connector or a plug connector is fitted in accordance with the manufacturer’sinstructions,with a welding cable of maximum cross-sectional area. The connection issubjected to 10 pulls with a force of 40 N/mm2 of the cross-sectional area with a maximum of2 000 N applied to the welding cable.The force of each pull is gradually increased from zeroto the specified value in 1 s and maintained for 1 s.