Selective Hi-Pot Testing Policy for Power Supplies

Background

The system power supply is critical component the treatment device.

As part of standard production, each unit undergoes a Hi-Pot (High Potential) test at the end of the manufacturing line, verifying the integrity of the insulation system.

This test is executed only once using a 3kV load for 1 second, as defined in the Acceptance Test Procedure (ATP). However, questions arose regarding the necessity of repeating the Hi-Pot test during post-market service, particularly when repairs involve only mechanical or low voltage elements.

Initial Risk Concern

While the Hi-Pot test is effective for verifying insulation integrity, repeated exposure to high-voltage stress may degrade internal components and reduce long term reliability. Therefore, a risk-based evaluation was initiated to determine when repeat Hi-Pot testing is technically justified and when it may be safely omitted.

Technical Review and Risk Mitigation Actions

1. Component Design Verification

   • The system power supply of the shelf internal power supply module of well-known MFR such as XP Power and Mean Well.   

   • The internal modules are individually undergo Hi-Pot tested and certified by their manufacturers.

   • The integration as system power supply includes only low-voltage components beyond these internal power supplies.

2. Failure Mode and Service Activity Analysis

   • Most service repairs are limited to:

     • Replacing external plastic housings,

     • Repairing filter PCBA or harnesses,

     • Cosmetic modifications.

   • These parts reside in the low-voltage domain and do not influence the high-voltage circuit.

3. High/low Voltage Architecture

   • A clear separation exists between the high-voltage and low-voltage domains, simplifying failure isolation and impact assessment.

   • Service repairs rarely extend to the high-voltage components.

4. Service Policy and Traceability

   • Hi-Pot test results at production are serialized and archived.

   • No historical evidence of insulation failures in post-service units without power module replacement.

5. Regulatory Justification

   • IEC 62353 supports risk-based post-repair testing.

   • The standard allows insulation resistance or leakage current alternatives when high-voltage paths remain unmodified.

   • Aligns with the proposed selective test approach based on the designer and MFR recommendation.

Execution and Implementation Plan

• Policy Definition: Hi-Pot testing post-service is mandatory only when:

  • The internal power supply module is replaced or reworked.

• All other cases (Mechanical, cosmetics or low-voltage repairs): Hi-Pot test is waived.

• Documentation Update:

  • Test Requirements and Service ATP to be revised accordingly.

  • Guidelines to be incorporated into technician training and repair checklists.

Conclusion

Based on:

• The modular system design with certified internal power supplies.

• Clear separation between voltage domains.

• Compliance with IEC 62353 for medical equipment testing post-repair..\

A selective Hi-Pot testing strategy was approved. 

This decision:

• Reduces unnecessary component stress,

• Streamlines service workflows.

• Maintains compliance and safety.

• Improves equipment longevity.

The revised policy reflects a practical, risk-based engineering judgment that supports both regulatory alignment and operational efficiency.