Non-sparking 'n'

Background

This protection prevents sparks or any exceeding surface temperature from occuring in normal situation for which the motor is certified.

The EHSRs of ATEX Directive corresponding to category 3 must be followed:

• Equipment must be so designed as to prevent foreseeable ignition sources which can occur during normal operation.
• Surface temperatures must not exceed the stated maximum surface temperatures under intended operating conditions included network tolerances.

To be installed in Zone 2, the motor must comply with Category 3 requirements.

The explosive gas penetrates inside the motor without any risks of explosion because:

• All parts inside the motor do not exceed the temperature class for which the motor is approved
• No risks at all that sparks occur due to the material selected for the relevant components, specific design regarding connection.

Standards concerned with the protection type 'n':
EN 60079-0: 2004-03	Electrical apparatus for explosive gas atmospheres. Part 0: General requirements.
EN 60079-15: 2005-10	Electrical apparatus for explosive gas atmospheres. Part 15: Type of protection 'n'.
EN 50014: June 1997	Electrical apparatus for potentially explosive atmospheres. General requirements.
EN 50021: April 1999	Electrical apparatus for potentially explosive atmospheres. Type of protection 'n'.
IEC 60079-0: 2004-01	Electrical apparatus for explosive gas atmospheres. Part 0: General requirements.
IEC 60079-15: 2005-03	Electrical apparatus for explosive gas atmospheres. Part 15: Type of protection 'n'.
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Marking	Old EN	IEC / New EN
Symbol for type of protection	EEx nA	Ex nA

Note: For non-sparking motors, the gas group is not relevant, only the minimum ignition temperature has to be taken into consideration.

Design:

• New requirements have been introduced in standard 60079-15:2001-02 and EN 50021: April 1999 regarding the minimum mechanical gap between stator and rotor:
  This requirement is the same as for increased safety motors EEx e/Ex e for use in zone 1.
  It reinforces the safety aspect in running performance and also during the start up of the motor.

In addition to the minimum gap between the rotor and the stator, the non-sparking inside the motor is ensured by:

• Minimum value for clearances and creepage distances according to the latest standards
• Insulation material with the highest class of resistance to tracking
• Minimum IP 54 protection
• Clamping of conductors