What are the key factors to consider when selecting VFDs for redundancy purposes?

1 Redundancy types

Different types of redundancy can be implemented in VFD systems, depending on the level of backup and protection required. Parallel redundancy involves two or more VFDs in parallel, with only one active at a time; this provides high availability and reliability, but increases cost and complexity. Series redundancy involves two or more VFDs in series, all active at the same time; this provides some fault tolerance, but reduces performance and lifespan. Hybrid redundancy combines parallel and series redundancy to provide a balance between availability, reliability, performance, and cost; however, it requires more sophisticated control and coordination.

2 Selection factors

When selecting VFDs for redundancy purposes, there are several factors to take into account, such as the load characteristics, system configuration, control strategy, and cost-benefit analysis. For example, a constant torque load may require parallel redundancy, while a variable torque load may allow for series redundancy. Additionally, a single motor may require parallel redundancy, while multiple motors may allow for series or hybrid redundancy. Furthermore, a manual control may require parallel redundancy, while an automatic control may allow for series or hybrid redundancy. Lastly, a high criticality load may justify parallel redundancy, while a low criticality load may tolerate series redundancy. All of these factors need to be considered when selecting VFDs and the appropriate type of redundancy.