Creepage distance increased safety

Special-purpose motors such as increased safety motors, flame-proof or explosion-proof motoi s must be checked for gaps, clearances and creepage distances of all the mating parts forming flame paths. The construction of these motors must follow lEC 60079 as noted in the list of standards. 

Table 6.18 gives a survey of these relations according to IEC 60664-1 for normal industrial equipment compared with the specifications according to IEC 60079-7 and EN 50019 for increased safety - e Figure 6.39 shows creepage distances at a terminal block. 

In the high voltage range, the creepage distances are identical to those for pollution degree 3. It should be remembered that increased safety asks for IP 54 as an adequate ingress protection degree for the enclosure (with bare live parts inside). 

An increased motor speed (at a higher frequency) may cause an increased explosion pressure in a flameproof enclosure (see Section 8.1). Bearings may show an increased temperature and exceed the temperature class of the motor where fitted outside the flameproof enclosure (Fig. 6.85(b)). In terminal compartments according to increased safety - e clearances and creepage distances at an increased voltage may not comply with the requirements... 

---