Requirements for the electrical strength of “n” type electrical equipment for explosion-proof purposes

The insulation dielectric strength of “n” type electrical equipment to ground or frame shall comply with the following provisions, except when the circuits installed in the electrical equipment are directly connected to the equipment frame or connected to the frame during equipment operation:

a. Tests as specified in the relevant industrial standards for the various components of electrical equipment, or

b. If the above test requirements do not exist, at least the test voltage shall be in accordance with the following 1) or 2) requirements, and shall not break down for at least 1 minute.

1) For electrical equipment with a peak supply voltage not exceeding 90 V or an internal peak voltage not exceeding 90 V, the test voltage’s RMS value is 500 V;

2) For other electrical equipment, or equipment with an internal peak voltage exceeding 90 V, the test voltage’s RMS value is the greater of 2 U + 1000 V or 1500 V.

It is permitted to use a DC test voltage in place of the specified AC test voltage. For insulated windings, it should be 170% of the effective value of the specified AC test voltage, or for the electrical clearance or creepage distance in the insulating medium, it should be 140% of the effective value of the specified AC test voltage.

Note: U is the higher value of the rated supply voltage or the highest voltage that occurs inside the equipment.

For equipment with electrically isolated components, the test voltage should be applied to each component separately at the appropriate voltage.