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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.
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Maximum Input Voltage
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I.T.E.
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Medical Equipment
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Basic
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Reinforce
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Basic
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Reinforce
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125V
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Air Clearance
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1.3mm
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2.6mm
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1.6mm
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3.2mm
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Creepage Distance
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1.5mm
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3.0mm
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3.0mm
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6.0mm
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250V
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Air Clearance
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2.0mm
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4.0mm
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2.5mm
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5.0mm
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Creepage Distance
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2.5mm
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5.0mm
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4.0mm
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8.0mm
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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
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Voltage Differences (Potential Difference in Vrms)
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With Opening
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Without Opening
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50 Vrms or less
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Air Clearance
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1.6mm
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1.6mm
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Creepage Distance
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1.6mm
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1.6mm
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51-150 Vrms
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Air Clearance
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3.2mm
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1.6mm
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Creepage Distance
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6.4mm
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1.6mm
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151-250
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Air Clearance
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6.4mm
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4.8mm
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Creepage Distance
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9.5mm
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4.8mm
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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.
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