4 types of VFD specifications
We have already talked a bit about customer specifications and the implication on VFD design. Unfortunately, those who shall primarily receive the message, may not be readers of our blog. Not yet, at least. Anyway, in this post we will introduce 4 types of VFD specifications. There is no such official classification. Instead, the four categories were created by us based on over 10 years of experience in VFD business. There is lot of observation and thoughts condensed into the characteristics of each type. So, let’s take a closer look!
User approach with regards to VFD specifications
End users may take very different approaches when creating VFD specifications. Some of them do it directly themselves while others hire an EPC (for larger projects) or some sort of consultant. One group takes a pragmatic approach while other group makes it very complicated and difficult. With some end users you can discuss specific deviations or even propose an alternative solution with superior performance. Others might be quite open, but have few key points where they have a clear vision how the solution shall look like. You might have hard time proposing an alternative solution. Then there is the last group – users who are not willing to discuss any exception. Sadly, they may not even know where the specific requirement comes from. In fact, that might be an explanation why they do not want to discuss it. The specs are often written in a way that no manufacturer can 100% comply. Therefore, everyone will have couple of deviations and it will be a lengthy painful process.
4 types of customer specifications
Type A: Pragmatic specification
Pragmatic approach or Fit for purpose
Pragmatic customers issue pragmatic specifications. They specify the required functionality without dictating the VFD manufacturer how to design and dimension each nut and bolt. These customers are also open for alternative proposals. In fact, they sometimes even encourage the manufacturer to provide an alternative solution when he believes that it better fits the purpose.
This fit for purpose approach is usually taken by companies that have solid know-how, vast experience and write the specifications themselves. They know what they want and they are capable to evaluate an alternative solution. Most importantly, they understand the background of their requirements. And finally, they can recognize an added value if it is proposed to them.
Yes, you are right. Such specifications make most sense. Dealing with such customer is clearly the best. Since he understand the system very well, he can also challenge you. At the same time, he usually accepts your arguments. This approach can be often seen by European end users and is beneficial for all involved parties.
⇒ Best approach
⇒ Built on mutual trust
⇒ There are only winners
⇒ Maximized value for customer
⇒ Best price/performance ratio
Note: End users with Type A specifications are not necessarily experts in the field of VFD (although some of them may be and they may even operate their own R&D centers). However, they have sound knowledge of electrical engineering in general and perfectly understand their application/process.
Type B: Balanced specification with few sticking points
This is quite common case. Balanced specification means that it does not define every detail like size of a regular screw, details on internal wiring or extensive painting instructions. Instead, it focuses on key features required to satisfy the application. The specification lists multiple requirements. Many of them just define the functionality or performance giving the manufacturer the freedom to propose what he believes the best solution. However, there are typically few points that the user really insists on. It might originate from the opinion of his technical experts, results from past issues etc. These points are not meant to limit the competition or there is at least no evidence of such attempt.
Similar to Type A, this specification is often written by the end user directly or eventually by a third party engineering/consulting company. Stated requirements seem logical and consistent. User is generally quite open for alternatives unless it is one of these sticking points that he really insists on.
⇒ Reasonable approach
⇒ Generally beneficial for all parties
⇒ Importance of mutual understanding and open dialogue
Note: User with Type B specifications usually also have expertise in electrical engineering, but some of them prefer to outsource the responsibility to create VFD specifications to a third party. This approach is generally fine, but heavily depends on the specific third party.
Type C: Specification fitting one particular solution
Fit for very specific solution or fit for one particular vendor – potential red flag
In this case it is quite black and white. As a manufacturer you are either the lucky one with the right technology or the one with bad luck. Key question here is whether this limitation to a very specific technology makes sense and whether it brings any advantage. More importantly, it shall be carefully reviewed whether it is actually legal or not.
Now, we are not lawyers so below statements may not be 100% bullet proof. But the basic essence shall be. In some cases the user is free to decide for a specific technology or manufacturer. Like if you buy a car: You may have your favorite brand and go for that brand again. Similarly, the user can basically go for a single source. However, there is number of cases where such behavior is breaking the law and will be considered illegal. A typical example of illegal limitation of competition is if the end user is a government-owned company or if the project is co-financed from public money (e.g. EU funds).
Type C specification is very questionable. It does not (only) specify the functionality and performance, but also the way the design shall be made. Limitation of competition results in higher purchase price. Legally it might be fine, but as soon as the funding comes from the government, public funds etc it may quickly become illegal. This type of specification usually triggers one or more red flags.
The limitation of competition may not be obvious in the specification unless you know the VFD market very well. However, for a VFD expert it is easy to find a combination of “innocent” technical requirements that fits to one single manufacturer.
⇒ There are better ways
⇒ Limited competition
⇒ Normally not in the interest of end user
⇒ May be illegal, especially if limitation done intentionally
Type D: Specification ala Google search
Specification based on copy+paste of unverified Internet content, various standards, specs of other companies… all of that together
This type of specification is…hmm…how to be politically correct?…difficult to deal with. It may be written by end user himself, but more often it is delegated to a third party. That is already the first issue. The third party, being eventually paid per page, will blow up the specification into several hundreds of pages. After the motto: The longer the better.
The requirements are a blend of everything that can be found on the internet. It is a pot where someone puts in some questionable information found by using search engines, mixes it with several international standards, copies specifications of other companies and spices that all with few more “ads-on”. Consequently, there is probably no way that any manufacturer could meet all the requirements. They may not even make sense. Therefore, a list of deviations becomes inevitable. That will most likely trigger a lengthy approval process with uncertain result and big portion of frustration. If the author(s) of specification does not know the reason for certain requirement he will likely have difficulty to approve your exception no matter how good is the explanation that you provide.
Finally, specification like this is so long and complex that certain chapters may be in contradiction with one another. It would usually require the manufacturer to put their standard design up side down or to design a unique “one off” product for that particular project. What is even more annoying that the manufacturer would have to put aside his proven design, best practice and experience and would be forced to manufacture something that he does not want, has no experience with or does not feel confident. Moreover, he would still be responsible for that “experiment”. Is that fair?
Our judgement is clear: The less such specifications are issued the better for the entire VFD community. Going even further I would suggest that authors of such specifications design, assemble, test, install and commission the VFDs themselves. They know better how to do it than anyone else.
This type of specification is – FORTUNATELY – very rare in western world. However, in certain countries they may take that road. Good luck and strong nerves!
⇒ Bad approach
⇒ Inefficient process and lengthy discussions
⇒ Waste of time and resources
⇒ High likeliness of conflicts in requirements
⇒ Toxic
Verdict
In our personal view the 4 types of VFD specifications can be ranked by using emoticons as per below:
What is your experience? Which of these 4 types of VFD specifications characterizes the best the documents you work with? Feel free to leave us a comment at the end of this article or drop us an email.
Summary
We have introduced above 4 types of VFD specifications. Of course, some specifications may fall into multiple categories. In any case, one of them will dominate. Specifications are fundamental to define requirements and obtain a suitable product or system. By saying that it is certainly not our intention to downplay their importance. However, it is equally important that the specification serves its purpose, is practically oriented, does not discriminate alternative proven solutions and also complies the law and anti-trust regulations (if applicable).
References
[1] VFD specifications: Too much – too little? https://mb-drive-services.com/projspec-1/
[2] Medium Voltage AC Drives, https://new.abb.com/drives/medium-voltage-ac-drives
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2 Comments
Simone · March 7, 2021 at 12:05 am
Interesting article. I would add one point. There are so many VFD manufacturers in the world, and they all produce different drives: some are really high quality, some are really poor. If you decide to purchase from all possible manufacturers, then you need a very long, detailed specification that will inevitably describe a drive that simply does not exist. You need to do this because most of the manufacturers are far from high standards and quality, so you cannot trust their standard design and you need to specify each and every bolt. It would be a good way to narrow the vendor lists to those few manufacturers that can really prove the quality of their products with successful installed based and reference lists. The success of a drive is not only based on technical data and features, but also on what there is behind it: service, R&D, financial stability, experience, know-how, etc… all things that cannot be put into a specification.
admin · March 8, 2021 at 2:43 pm
Thank you Simone! I really like your comment. Finding the balance is not easy – I agree. There are some ways to disqualify or discourage the poor quality suppliers. For example by requiring longer warranty period or specifying site acceptance tests with clearly defined performance and high penalties for non-compliance. It will not be bullet proof solution but as said, it probably discourages the worst performing manufacturers. Another option is to request references and really check in detail some of them and talk to the end users.
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