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How does IEC 60335-1 relate to industrial power supplies?

Wednesday, August 31, 2022

In addition to the safety standard IEC 60950-1 (Industrial and Technology Equipment), IEC 60601-1 (Medical Electrical Equipment) and more recently IEC 62368-1 (Audio/Video, Information and Communication Technology Equipment), you may see reference to the IEC 60335-1 “safety of household and similar electrical appliances” standard on industrial power supply datasheets.

At first glance,” this might seem an odd choice for an industrial power supply to require. There are, however, significant amounts of AC and DC input electrical appliances that would normally be used in catering, light industrial shops, commercial cleaning and agriculture that are being operated where they could pose a danger to the general public. You may have noticed restaurant grade appliances in some high end home domestic kitchens for example.

Although an industrial power supply safety certification for 60335-1 does have to consider the common hazards in and around the household, it does exclude, for example, unsupervised children aged from three to eight years playing with the appliance. In fact, this reflects an industry wide change to standards in general. The combining of the Information Technology Equipment (ITE) IEC 60950-1 standard with the audio, video and similar electronic apparatus (IEC 60065-1) standard into IEC 62368-1 became necessary as smart devices evolved. Medical equipment under IEC 60601-1 has now addressed the expanding use of home-healthcare.

What are the challenges for obtaining 60335-1 on a power supply that has been designed for 62368-1?

Creepage and clearance can be more stringent than 62368-1 when the internal working voltage is between 250 and 300V. The working voltage is the voltage that is across an insulator under normal conditions. 8mm of clearance maybe required between input and output. Clearance is the distance measured through air. Creepage is measured on the surface of the insulator. Figure 1.

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Figure 1: Creepage and clearance

The Ingress Protection (IP) rating may be higher, depending on where the appliance may be used. This would affect external power supplies (adapters), as open frame products would normally be inside the appliance.

TDK-Lambda has low power products like the 30 to 60W 2” x 3” footprint CUS30M and CUS60M (Figure 2) which have EN 60335-1 certifications in addition to 62368-1 and 60601-1. The 250W rated 2” x 4” CUS250M (Figure 3) has 62368-1 and 60601-1 certifications, but complies with 60335-1, making it simpler for the appliance designer to obtain certifications.

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Figure 2: CUS30M and CUS60M power supplies

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Figure 3: CUS250M power supply

The trend is increasing for industrial power supplies to be designed for use in multiple markets, having both IEC 62368-1 certification and the more stringent IEC 60601-1 medical standard. The ability to operate without the need for an earth conductor (Class II) and with lower leakage currents may offer commercial advantages to appliance designers.

Power Guy