Shenhai Explosion-Proof
Increased safety electrical equipment, denoted by the symbol “e,” is a specialized type of explosion-proof electrical equipment widely used in industrial settings with flammable gases. These devices are designed according to explosion-proof principles, where the rated voltage of the electrical supply does not exceed 11kV (AC rms or DC). They are made to operate without generating sparks, arcs, or hazardous temperatures under normal or certain abnormal conditions.
Explosion-Proof Principle
According to the principle of explosion-proof design, electrical equipment that does not produce sparks, arcs, or dangerous temperatures in normal or approved abnormal conditions, and operates within the rated voltage limit of 11kV, can be designed and manufactured as increased safety electrical devices. Clearly, equipment that fails to meet these conditions cannot be made in this style.
Instead of using an “explosion-proof enclosure” like flameproof electrical equipment, increased safety devices employ mechanical and/or electrical reinforcement on the various components. Based on the necessary and sufficient conditions for combustion and explosion, these measures enhance the safety and reliability of the devices. This approach involves specific structural measures and safety requirements to ensure that the electrical equipment does not become an ignition source in flammable environments.
Application and Safety Measures
Increased safety electrical equipment, typically used in categories like AC motors (including rotating motors, transformers, electromagnets), lighting (including inductive ballasts for lighting), resistance heaters, batteries, junction boxes, current transformers for instruments and non-instrumentation purposes, is designed considering mechanical structure, enclosure protection, electrical insulation, wiring connections, electrical clearances, creepage distances, and limiting temperature rise.
For manufacturing other electrical devices in this style, additional technical measures and safety requirements are considered beyond the general requirements of increased safety design.
Important Considerations
1. Under installation conditions, the operational parameters of electrical components should not exceed 2/3 of their rated nominal parameters.
2. Heating elements should not produce hazardous temperatures beyond the limit or adversely affect surrounding circuit units.
3. Resistive elements should be thin-film or wire-wound resistors.
4. Inductive components should prevent the generation of back EMF upon circuit interruption.
5. Capacitive elements should be solid insulating medium capacitors, avoiding electrolytic or tantalum capacitors.
6. Switch components should be protected with flameproof enclosures.
Generally, this explosion-proof style does not differentiate between explosion-proof levels. If necessary, specific levels like IIA, IIB, or IIC can be determined through testing for high-voltage or high-capacity increased safety AC motors. The device protection levels, like level b or c, are also considered in practical use, represented as Gh or Gc levels.
The enclosures of increased safety electrical equipment are usually made of metal plates (such as certain steel and aluminum alloys), cast iron, cast aluminum, and engineering plastics.