VFD Accessories
Home » Blog » VFD Accessories » AC reactor VS DC reactor in VFD

AC reactor VS DC reactor in VFD

AC reactors reduce harmonics, mitigates transient conditions and helps to maintain proper phase to phase voltages. DC reactors will also mitigate harmonics however it will provide more harmonic attenuation than a equally sized AC reactor.

Both reactors will increase the conduction angle of the DC current pulses flowing through the rectifiers and thereby reduce the harmonics on the supply.
The AC line reactor will provide a high impedance path for fast transients and reduce the transient voltages across the rectifiers providing a level of transient voltage protection for the input rectifier.
Both reactors will reduce the charging current to the capacitor bank under a voltage surge condition, so help to protect the rectifier from current surges resulting from voltage surges/transients.
The AC line reactor has an AC flux in the iron, with a high harmonic content, and so has both copper loss and iron loss.
The DC bus choke has DC with a superimposed ripple current, so the iron losses are lower.

Major differences? AC has higher losses but improved transient voltage protection for the rectifier. DC has lower losses, so higher efficiency.

Very important is that most DC bus chokes will need to be custom designed for the drive as they are commonly mounted inside the drive chassis. (and frankly, I can't think of any reason to use a bus choke over a line reactor if both would have to be externally mounted, the internal mount is the only real advantage to the bus choke). Thus while there may be less weight for a bus choke, it's cost can be higher. On the other hand, multiple manufacturers have a wide range of ratings for 3 phase line reactors. To the point where the 3 phase reactor is practically a commodity and thus can be obtained very quickly and inexpensively. This is also important if a replacement is ever needed.True in most cases the reactor will need to be mounted external to the drive chassis, but this is offset by the cost savings of buying the reactor direct from a distributor. And not paying double markup necessary when it comes in the drive from the VFD OEM. Also, since the BUS choke is custom, there will be little option for varying the inductance and thus weighing cost vs performance for different applications. Reactors are commonly available in 1.5%, 3%, 5% and 10% impedance ratings.

You may also like:

It involves my proprietary power electronics, DC machines working in concert with AC grids, bi-directionally blocking the traditional amp draws of the AC grid and bi-directionally permitting forward emf ...
SV-PWM is actually just a modulation algorithm which translates phase voltage (phase to neutral) references, coming from the controller, into modulation times/duty-cycles to be applied to the PWM ...
For instance, let's take a transformer for an example. You test a transformer and you get short-circuit and open-circuit impedances and losses. Then, the most basic model for such transformer is a T circuit, ...
One of the ways these days that i check this process is by observing the winding process. By understanding the winding environment and not assuming anything, By taking part actively in DFM. By seeing what ...
For variable speed drives, there are two power semiconductor technologies employed: bridge rectifier and the output stage. The bridge rectifier is made up of power rectifiers which are connected directly to ...
service VSD blog: A deep observation of automation control industry, especially in AC motor variable speed drive for industrial motor controls.

Hot Tags

Featured

7 months back I was involved in a harmonics evaluation study at Budweiser. This was one of many I've participated in over the past 20 years, basically because in facilities like ... Most of variable speed drives are applying on high temperature fans, kiln head coal mill fans, kiln head surplus fans, raw mill circulating fans and so on. Two production lines ... Variable speed drive application in purification system optimizes the system performance, improves purification effect, reduces power consumption greatly. According to related ... The motor power factor does not make a big difference other than giving an idea of loading. In regards to the variable speed drive fixing power factor everyone is mostly correct. ... A soft starter is a basic device which will ramp up the speed of your motor to full speed over a preset time, easing mechanical stress and also easing the high inrush currents ...

What's New