Questions about FR and KH
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Dear instrumentation experts: Before starting my career 9 years ago, in the petrochemical industry, thermal relays were denoted by the symbol KH in circuit diagrams. Now I notice that in some of the client’s circuit diagrams, thermal relays are marked with the symbol FR; moreover, these FR symbols do not indicate features such as closing contacts, switches, or single-circuit protection.
Is there a clear technical distinction made in China between FR and KH? The concepts of current-limiting protection and thermal relays are too vague. It's best to have best practices.
I have been in this field for 14 years; previously it was the RJ designation, and later it became FR. KH is also used, but less frequently. What is the difference? I would like to ask those who work in design firms
I’ve never seen the term FR in overseas process packages.
FR thermal relay. The KH motor comprehensive protector offers better protection functions, adjustment ranges, and adjustment delay ranges compared to the FR
This generic answer. . . Absolutely dissatisfied
There’s nothing to do. I asked someone who works in the electrical field, and they said that the FR stage is not as powerful as the KH stage; currently, KH stages are used more often, while FR stages are used very rarely these days.
The idea is this: as technology evolves, I hope that domestic experts in this field can write a comparative overview of FR technology and KH technology for me.