Spacing Requirement

In this section:

The clearance and creepage distance requirements were designed to isolate hazardous voltage (overvoltage transients) that may enter the equipment, therefore preventing hazard contact to the client.

Spacing graph

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CLEARANCE: The shortest distance between two conductive parts, or between a conductive part and the bounding surface of the equipment measured through air.

CREEPAGE DISTANCE: The shortest path between two conductive parts or between a conductive part and the bounding surface of the equipment, measured along the surface of the insulation.

Note: Bounding surface is the outer surface of the electrical enclosure, consider as though metal foil were pressed into contact with accessible surface of insulating material.

Requirement

Table 1 describes the differences between IEC 950 and IEC 601-1.

Maximum Input Voltage

I.T.E.

Medical Equipment

Basic

Reinforce

Basic

Reinforce

125V

Air Clearance

1.3mm

2.6mm

1.6mm

3.2mm

Creepage Distance

1.5mm

3.0mm

3.0mm

6.0mm

250V

Air Clearance

2.0mm

4.0mm

2.5mm

5.0mm

Creepage Distance

2.5mm

5.0mm

4.0mm

8.0mm

For I.T.E. and medical equipment, the spacing requirement mention in table 1 are being use to provide a method of insulation as illustrated above.

Class 2

Voltage Differences (Potential Difference in Vrms)

With Opening

Without Opening

50 Vrms or less

Air Clearance

1.6mm

1.6mm

Creepage Distance

1.6mm

1.6mm

51-150 Vrms

Air Clearance

3.2mm

1.6mm

Creepage Distance

6.4mm

1.6mm

151-250

Air Clearance

6.4mm

4.8mm

Creepage Distance

9.5mm

4.8mm

Equipment

Spacing requirement for UL1310 equipment is different from I.T.E. and medical equipment.

The spacing mention in table 2 are between live parts of opposite polarity and between live and dead metal parts.

Note: please refer to your safety engineer if the enclosure is made of metal.