Active Harmonic Filters Offer the Best Properties for a Low Harmonic Drive

Active Harmonic Filters are installed in parallel with a standard 6-pulse drive fitted with a small filter.  This allows the drive to operate even if the filter is not in operation.

Serial vs Parallell installation

Using a parallel filter solution offers many advantages relating to sizing, foot print, system losses and availability. A parallel filter only needs to be sized to the mitigation load, generally 15-30% of the drive load unlike the serial solutions that have to be sized at 100+% of the drive load. As the shunt filter is smaller relatively to the drive the total system loss is smaller.

Lower system losses means less need for cooling and dramatically improve the Life Cycle Cost for the end user.

 Availability

The cost of a component failure/standstill must be included in any production process related investment calculation.  The cost of lost production income that can not be sold and potentially discarded is many times much more valuable than the capital cost of the equipment itself.  Hence the availability of the drive function is one of the most important aspects when designing a drive system.

Serial installation means additive Mean Time Between Failures(MTBF). This means a serial filter will have 50% lower MTBF compared to a shunt filter.

Other more practical issues such as sourcing 6-pulse drives is also much easier compared to sourcing special AFE drives or 18-24 pulse units in case the drive itself needs to be changed.

Foot print and weight

Availability of drive function is the primary factor in keeping the production running.

Foot print lowers the system installation cost by reducing cost of cabinet and floor space. In retrofit projects as well as space constrained segments such as marine and offshore foot print and weight management is often crucial.

Installation

The design of many Active Harmonic Filters allow very compact installations where the cabinet is utilised at a maximum. The AHF’s power density is among the highest in the world among active filters. The filter design enables easy and economical use of cabinet footprint. Integrating the filter with single and multiple drives is simple and the filter normally does not need on site commissioning by external service engineers.

Future proof  and flexible design options

It is good to ensure that the installed load can grow and change over time. Some AHF adapt to the load and more AHF capacity is easy to add by separate modules. The solution is flexible and can be installed centrally compensating many drives.

Commissioning

An easy to use web interface and commissioning software should guide the user through the process and allows for customer specific parameters settings. The filter is simple to configure to automatically focus on harmonics and use extra capacity for power factor correction.  Integration through Modbus and Ethernet is standard.

Guarantee risk

By using a shunt installation the guarantee risk is reduced. The availability of the fundamental drive function is very important to the end customer. The AHF in shunt does not risk the drive function because even if the AHF fails the parallel installation allow the drive to operate.

In larger installations with multiple AHFs in parallel the filter function availability is vastly improved as the compensation is only partly reduced if one out of several filters fail.

Modern running master functionality allow a group of AHFs to automatically reconfigure themselves with a new master-slave relationship even if the original master-filter would stop. Automatic alarm functions to the responsible technician allow early and prompt response.

Finally, the drive + AHF system does not have issues with high frequency switching ripple that can cause EMC issues in larger AFE installations.