Small wind / Buyer questions
Electrical configuration
How much energy remains in a wind converter’s DC-link capacitors after shutdown?
The short answer
A stopped converter can retain energy in its capacitors. The ideal stored energy is E = ½CV², but safe access must follow the actual manufacturer’s isolation, discharge and absence-of-voltage procedure rather than an energy calculation alone.
Understand the interface decision
Disconnecting one source does not necessarily discharge a DC link, and another source can recharge it. Capacitor values, parallel branches and discharge circuits affect the decay. A failed discharge path can make the normal waiting-time assumption invalid. A dark display or a stopped rotor is not a measurement of the electrical condition inside the converter.
A wind electrical interface must be checked across its operating envelope, including transitions and credible faults. The following is an engineering review method; it does not establish compatibility between unnamed turbine, generator, converter or controller models.
Put these inputs in the review record
Use a project-specific worksheet to capture the following information. For each entry, name the document, revision and person responsible for resolving any uncertainty.
- Total connected capacitance and the highest credible DC-link voltage. Identify the exact configuration and the supporting document.
- Every possible charging source, including linked converters and auxiliary circuits. Keep the design assumptions visible in the project record.
- The specified discharge arrangement, waiting period and verification points. Name the responsible reviewer and resolve any missing information.
- The manufacturer’s service procedure and the qualified personnel responsible for applying it. State how this entry will be verified during acceptance.
Define the acceptance boundary
Keep the energy estimate as a design input for discharge and protection assessment. Do not use an illustrative capacitance or voltage as a servicing instruction. Acceptance requires a defined isolation boundary and verification method for the selected equipment, including abnormal conditions.
An engineer may compare two capacitor arrangements using the equation to understand relative stored energy. That comparison does not establish either arrangement as touch-safe. The maintenance record should identify the equipment-specific procedure that controls access.
Sources
Examples are illustrative. Confirm product-specific performance, compatibility and supply scope in the applicable documents.