StackFET and IEC 60950

Posted by: kafka on 05/05/2015

Hi,

Please can you help me how to determine creepage and clearange distances accoring to the IEC 60950? The power supply is three phase, so the power supply is 3x230VAC, and after rectifying I have about 564VDC. I know it depend on pollution grade (two kind of devices. One in first grade and one in second) and material group (I assume IIIb).

Comments

Hi,

Considering 3-phase input line-line voltage is >300V for a 230V L-N supply.

For Pollution degree II, material group IIIb

Clearance distance required (primary-secondary) is 6.4mm based on peak drain voltage (<1400V)

Creepage Distance required (primary-secondary) is 8mm to 10mm based on the peak drain voltage (800V - 1000V respectively)

Regards,

PI-NANO

Creepage differs from my calculations. To be more specific I was asking about reinforced insulation.

Hi,

Sorry, it was my mistake.

Creepage distance is defined as the shortest path between two conductive materials measured along the surface of an isolator which is in between. Maintaining a certain creepage distance addresses the risk of tracking failures over lifetime. The generation of a conductive path along the isolator surface due to the high voltage applied over long time is more related to the RMS value and depends on environmental conditions, which are described by a pollution degree and the material characteristics of the isolator (see CTI Comparative Tracking Index).

Creepage Distance required (primary-secondary) is 2*6.3mm (12.6mm) based on the approximate RMS voltage of 600V.

For REINFORCED INSULATION, the values for CREEPAGE DISTANCE are twice the values for BASIC INSULATION in table 2L of IEC 60950.

Regards,

PI-NANO