19.1.4 Protection from break of secondary winding of electromagnetic valve
[Basic requirements]
Electromagnetic valves which operate at hazardous voltages and incorporate the primary winding
(for pulling) and the secondary winding (for holding), and its surrounding insulators shall be
constructed in such a way to avoid the risk of smoke emission or ignition even if the secondary
winding should break, in order to prevent smoke emission, ignition and fire hazards.
[Design standards]
1) Flammable material shall not be located in close proximity to the location at which arcing might
occur due to the break of the secondary winding (See Fig. 2 in ANNEX 3 "How to obtain special
protection area").
2) Fire-retardant materials rated UL 94V-0 or higher are not considered to cause the emission of
smoke or ignition even if they are located in close proximity to such potential arc sites.
Note: Electromagnetic valves may arc due to chattering of the contact when the secondary winding
breaks.
[Criteria]
1) Compliance is determined by visual inspection.
2) Compliance is determined by checking the special protection area and on the basis of the fire
retardancy of materials.