Inverter accessories
Home » Blog » Inverter accessories » DC Chokes on variable frequency drives

DC Chokes on variable frequency drives

From a manufacturing economics standpoint, there is often a trade off in the decision to add a DC bus choke or not based on its ability to reduce the DC bus ripple. This is because it can reduce the DC bus capacitance necessary to present a clean DC source to the transistors. For some AC drive manufacturers who have the internal capability to wind their own component chokes, this often represents a component cost benefit compared to buying capacitors from outside vendors and being more subject to market volatility. On the other hand if the AC drive manufacturer IS also a manufacturer of capacitors, it works exactly the other way around.

I believe this is why we often see small component class drives being made without DC chokes primarily by companies, mostly in Asia, for whom capacitors are a very low cost commodity. When EU and US manufacturer make larger variable frequency drives, it's usually less expensive for them to wind chokes, but that option is often perceived to be too physically large for component class drives so they farm out their designs and production to Asian manufacturers. Ironically then, users will add an external AC reactor anyway, but fail to observe that the overall footprint is now larger than it would have been with a DC choke.

I attribute this to the same false market perception that society uses in buying airline tickets. We now shop on the internet based on one criteria, price of the ticket. The airlines have finally figured that out, so they now appear to have lower ticket prices, but charge us extra for bags, snacks, leg room etc. and we actually are paying MORE than we used to. So to relate that back to the AC drives, the market demanded smaller and smaller packaging of VFD drives, which became a primary selection criteria, leading to the smallest physical package, the ones without DC chokes, being dominant in that low kW realm to the point where virtually everyone else gave up and joined the party.

That said, there is still validity to the added protection for the front end of the AC drive provided by the reactor compared to a DC choke. If there are multiple AC drives in an enclosure however, that benefit can still be realized with one larger reactor ahead of the entire inverter drive input power circuit.

Post a Comment:

    
Calculate (2 + 7) =

You may also like:

The power industry has many tentacles. Energy production is one key subset, the design, manufacture, installation and operation of hydro, nuclear, fossil, renewables, etc is continuing to grow especially in ...
I don't believe the interchangeable battery pack idea is workable. Who is going to own the battery packs and build the charging stations? And what happens if you get to a charging station with a nearly dead ...
When synchronous generators (alternators) are connected in parallel with each other on an AC grid, they are all operating at a speed that is directly proportional to the frequency of the AC grid. No ...
Soft starters and variable frequency drives are two different purpose products. VFD is for AC motor speed control, it's not only change the output voltage but also change the frequency; Soft starter is a ...
In electric motor stop, the traditional control ways are accomplished by momentary power cutting off. But in lots of applications, it's not allowed the motor instant shutdown. For example: high-rise buildings, ...
Gozuk Service Gozuk Blog: all about electric motor control & drives industries development in energy saving applications.

Featured

Like pumps, fans consume significant electrical energy while serving several applications. In many plants, the VFDs (variable ... energy consumedA frequency inverter controls AC motor speed. The frequency inverter converts the fixed supply frequency (60 Hz) to a ... Motor starter (also known as soft starter, motor soft starter) is a electronic device integrates soft start, soft stop, ... Soft starter allows the output voltage decreases gradually to achieve soft stop, in order to protect the equipment. Such as the ... Soft Starter reduces electric motor starting current to 2-4 times during motor start up, reduces the impact to power grid during ...

In Discussion