1. Cautions in Series Operation

When using our power supplies in a series connection, please observe the precautions below.
In a series configuration, high voltage may be applied between each power supply’s output (secondary side) and FG (frame ground), requiring special safety considerations.

• (1)Regarding Safety Standards
  If the total output voltage exceeds the SELV limit, safety certifications will no longer apply.
  Our products are designed based on the SELV (Safety Extra-Low Voltage) requirement of 60 V DC or less. However, when connected in series, the combined output voltage may exceed the safe voltage limits (42.4 V peak for AC or pulsating waveforms / 60 V DC).
  In such cases, the existing safety approvals become invalid.
• (2)Concerns Regarding Increased Voltage Between Output and FG
  Do not connect the output GND or auxiliary-function GND to the FG.
  If the secondary side is grounded, the voltage between the top unit’s output and FG in the series stack will rise considerably. As a result, the grounding capacitors between output and FG, as well as connectors for functional terminals, may be subjected to voltage stress beyond their rated limits.
  For detailed component voltage ratings, please contact our support team.
• (3)High Voltage Between FG and Output Lines
  Even when the secondary side is not grounded, the series configuration still causes high voltage to appear between the output and FG.
  Therefore, any issues such as foreign-object intrusion or circuit shorting can be extremely hazardous.
  Please ensure thorough safety measures, including adequate insulation design and foreign-object prevention, as would be required for equipment handling high voltage.
• (4)Notes for Equipment Integration
  Even after installation in your equipment, high voltage will remain between the FG potential and the output lines.
  Please take all necessary precautions and treat the design as a high‑voltage application.