What is the leakage current limit for common mode inductors used in medical equipment? How can it be tested?

The leakage current limit is typically ≤100μA ~ 1mA, depending on the application category.

 Test method:

 Limit basis: For patient-contacting equipment (such as monitors), the requirement is ≤100μA (patient leakage current according to IEC 60601-1 standard). For non-contacting equipment, a higher value (such as ≤1mA) is allowed, but it must comply with the safety isolation distance.

 Test method: Insulation resistance test: Apply voltage using a 500V/1000V DC megohmmeter to measure the resistance between the winding and the grounded enclosure, ensuring it is ≥100MΩ (mandatory requirement for medical grade). Direct leakage current measurement: Monitor long-term leakage current in series with a microampere meter at rated voltage, focusing on whether it exceeds the standard after exposure to hot and humid environments or aging. Voltage withstand test: Apply 1.5~2 times the rated voltage (e.g., AC 1500V for 1 minute) and monitor the breakdown current to ensure the insulation structure is free of defects.

 Failure mode: Aging of insulating materials, cracking of solder joints, or cracks in the magnetic core may lead to a sharp increase in leakage current, necessitating early screening through accelerated life testing (ALT).