Glossary · Automation fundamentals, platforms and components
DC link (intermediate circuit)
Also known as: DC bus, Intermediate circuit
German: Zwischenkreis
In power electronics, the DC link (intermediate circuit) is the DC voltage stage of a frequency converter or servo drive between the rectifier and the inverter, usually buffered by capacitors.
- Automation components
In one sentence
The DC link is the capacitor-buffered DC voltage stage of a frequency converter between rectifier and inverter.
Example
Several servo drives share a common DC link, so braking energy from one axis can be used by the others instead of being burned in a brake resistor.
How it applies
- Engineering: DC link voltage is typically several hundred volts. Shared DC links, brake choppers and regenerative supplies are designed around it.
- Maintenance: DC link capacitors can hold a hazardous voltage for minutes after the drive is disconnected. This is Stored energy and must be considered in isolation procedures.
- Documentation: Instructions must state the discharge time printed on the device and require checking for absence of voltage before work. Warnings about DC link voltage belong in the safety chapter and at the relevant maintenance steps.
DC link vs. mains supply
Disconnecting the mains does not immediately make the DC link safe. The drive may also be fed back by a motor that is turned by the load, which can recharge the DC link. Lockout procedures should cover both.