Which one is your VFD hero?
VFDs, together with their rotating partners (motors) perform lot of work behind the scene. As we already know, there are multiple VFD topologies available on the market. While they all fulfill the basic purpose, such as soft starting of the machine and speed or torque control, each platform has particular strengths. In this article we will briefly introduce some of them. Here comes the blog post Which one is your VFD hero?
The Friendly Gentleman
Bonjour! Nice to meet you. I am The Friendly VFD, also called VFD gentleman. Motors belong to my best friends. They appreciate my gentle output waveform. Due to an output sine filter I can be a good friend with almost any motor – including those being born a bit earlier.
I am available either as air-cooled or a liquid-cooled variant. The first one is best suitable for lower power range while the second one fits best for higher power rating. Yes, you got it – we VFDs like to stay cool!
With me you can effortlessly achieve attractive energy savings. As just mentioned I am highly suitable for greenfield as well as brownfield installations. I have been here already for more than 2 decades with lot of brothers and sisters installed all over the world. Therefore, my platform is well proven and perfectly optimized.
Over the years I have collected lot of options and fashion accessories that you can choose from. All that to make sure that I will be a good companion at different occassions. Do we want to rock-n-roll?
The Compact Buddy
Hola! Meet me – I am The Compact VFD. One of my strengths is my footprint optimized design. I don’t consume too much of your valuable space thus saving your building cost or leaving the space for other equipment.
The direct to line (DTL) variant is a transformerless configuration. What does it mean? In case the grid voltage is of 6 kV class the input isolation transformer can be eliminated and I can work directly connected to the supply grid.
In the AFE variant I enjoy transferring the power in both directions: from the grid to the motor or vice versa (e.g. for regenerative braking).
There are actually two of us. The IEC 6 kV European boy and the NEMA 4 kV North American chum. Just to make sure that we cover your requirements and needs.
The Strong and Efficient
Hi there! Is there any load that requires medium to high power, superior efficiency and reasonable motor friendliness? If so, I would love to help out.
I don’t get cold feet when lot of power is required. In fact, I enjoy to let large compressors, fans or pumps to spin at speeds that the process controller wishes. And I do it very efficiently in order to save your pocket and the mother nature.
With my high pulse number on the grid side I make sure that the utility guy is happy and does not complain about high harmonic distortion. Compliance with harmonic standards is part of my DNA. Also my inverter part is pretty friendly. Indeed, I do not have any friction with my motor colleague. Therefore, you can be sure that we work together for many many years without any issues.
Finally I also think of the guys that are around to make the plant running. Featuring the highest level of safety and superior arc resistant design those people do not need to worry to work in the proximity of myself. I will certainly not cause any harm to them.
The Versatile and Dynamic
Hey! Let me introduce myself. I am The Versatile VFD. Where does the name come from? Well, I can cover many applications, including very special tasks, where many other VFD platforms do not fit.
High performance at low motor speed? No issue – just rely on me. Do you need dynamics? Well, that is my passion. Slow applications are boring – I prefer some action. For example rolling mill drives – that is a perfect match for me. Do you need a platform for special applications? Such as test stands? No problem for me. In fact, I love test stands.
When it comes to my muscles, they feature well-proven IGCT thyristors and diodes. My skeleton is the 3-level neutral point clamped (NPC) topology.
Additionally, my brain is really sharp. In fact, I may have multiple brains. Seriously, I am not joking. That is because I support a so called multidrive configuration. There are multiple inverter units connected to a common dc link. As such, I can supply multiple motors and control them totally independently from one another. Now you probably got it why I need multiple brains.
The Powerful and Robust
Howdy! I am the heavy weight champion. As far as power density matters, no other VFD technology compares with me. Therefore, you may call me the king kong of VFD world. My official name, however, is a Load-Commutated Inverter (LCI). While I already have couple of grey hair (being on the market for about 50 years) I will certainly stay around and keep doing the heavy lifting for you.
Some people claim that I am a bit picky in relationships with motors. Well, that is not quite true. In fact, I love all kind of motors and we like to party together. But I admit that for real job I only cooperate with synchronous machines.
My muscles are made of conventional thyristors. If needed, I can arrange my biceps in n+1 configuration. Therefore, I can still provide the full strength even if one muscle breaks down. Anyway, that is a very unlikely scenario as I am perfectly fit and robust. My topology simply keeps in shape and has proven it over the last 5 decades.
Another quality of mine is endurance. I will serve you reliably over the next 20, 30 or even 40 years. As long as you treat me in a good way you can really enjoy my faithful service for decades. You may need to brush up my brain (control system), but that is a common thing for all my colleagues above as well.
Final words
After all, which one is your VFD hero? Let us know in the comments below!
References
[1] Best VFD topology – One size fit all? https://mb-drive-services.com/best-vfd-topology-one-size-fit-all/
[2] Medium voltage AC drives, https://new.abb.com/drives/medium-voltage-ac-drives
