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Baphom8
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How do European Industrial Engineers Select the Fuse Size for a Motor Circuit?

03/13/2013 11:33 AM

Greetings. I am looking for some general information on how industrial engineers in Europe select fuse and wire size for motor cirucits in an industrial environment. Typical applications would use three phase low voltage in the range of 400 V to 500V. I understand how we use the NFPA 79 for Industrial Machines, the NFPA 70 for Structures, and the NEC for squirrel cage motor currents. So these are what we use in the US to select the fuse sizes based on a presecriptive approach. In Europe, the system is principle based, so the engineers have more freedom, but is their a guide they use, or a standard that helps them in the fuse and wire size selection process?

Again, this is a question about Europe, and how they select motor cirucit fuses in an Industrial environment. I appreciate everyone's desire to be of assistance, but I am requesting that the topic be limited to Europe, and I request that we limit the answers to folks who have first hand knowledge, and are not make educated guesses or speculating.

Thanks very much for your help with this question.

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Pathfinder Tags: europe european Fuse motor wire size
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PWSlack
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#1

Re: How do European Indutrial Engineers select the fuse size for a motor cirucit?

03/13/2013 11:39 AM

British Standard 7671 encompasses all here. Also, the fuses aren't there to protect the motor, for that is the job of the motor overload device. The fuses are there to protect the cables. Matching the overload and fuses is a practice called co-ordination, and there's plenty about it in the above document.

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Baphom8
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#2
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Re: How do European Indutrial Engineers select the fuse size for a motor cirucit?

03/13/2013 11:57 AM

Wow, thats super. Thanks very much. You are correct about the fuse protecting the wire and not the motor. I should have been more concise. My task is about selecting a fuse for a motor circuit, and in that light, I have to size the conductors accordingly, and that is when the fuse selection becomes relative.

Thanks very much for the fast resonse.

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Paulusgnome
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#3
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Re: How do European Indutrial Engineers select the fuse size for a motor cirucit?

03/13/2013 1:57 PM

The use of fuses to protect motor circuits is a poor choice of protection. If one fuse blows,the motor will single-phase, not a good thing. Until I started working from specifications from US customers, I had never seen a fuse-protected motor except in prre-1970`s equipment.

Better by far to use a circuit breaker.

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Baphom8
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#4
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Re: How do European Indutrial Engineers select the fuse size for a motor cirucit?

03/13/2013 2:55 PM

Oh? I had not thought of that. So in Europe they mainly use cirucit breakers?

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PWSlack
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#5
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Re: How do European Indutrial Engineers select the fuse size for a motor cirucit?

03/13/2013 4:29 PM

Predominantly overloads and fuses.

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pnaban
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#6

Re: How do European Industrial Engineers Select the Fuse Size for a Motor Circuit?

03/14/2013 1:44 AM

First select type of fuse suitable for the given application and select the size later as per manufacturer's recommendation.

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Baphom8
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#8
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Re: How do European Industrial Engineers Select the Fuse Size for a Motor Circuit?

03/15/2013 7:59 AM

So ad it pertains to europe, what would an industrial engineer use to guide them thruogh this process?

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Dodgy Solenoid
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#7

Re: How do European Industrial Engineers Select the Fuse Size for a Motor Circuit?

03/14/2013 4:26 AM

Please take a look at this document, it may explain what you're looking for:-

http://www.mep.hr/pdf/Coordination.pdf
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Baphom8
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#9
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Re: How do European Industrial Engineers Select the Fuse Size for a Motor Circuit?

03/15/2013 8:02 AM

Hey, thats a good one, thanks!

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obouill
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#10

Re: How do European Industrial Engineers Select the Fuse Size for a Motor Circuit?

03/19/2013 6:29 AM

IEC practices are detailed in the WIKI EIG ....

http://www.electrical-installation.org/enwiki/Basic_motor_protection_scheme:_circuit-breaker_%2B_contactor_%2B_thermal_relay
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