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DOL motor starting current & MCCB selection

Apostolos

Good morning

I have a question to address to more experienced people in here

I have a three phase DOL motor, 5.5kW, 11A with 130A starting current

This is going to be fed off a thermomagnetic MCCB

Before I see the starting current I was inclined to use a 16A MCCB

However I have now reservations due to the very high starting current

How can I select an MCCB in this case?

Is there a rule of thumb?

I am looking at a 40A MCCB now however this is more of an instinct rather than knowledge or experience.

Thanks!

  • 0

    How long does the starting current flow for ? rather than the normal C type, consider D type or even K curve may be more suited

    https://info.e-t-a.com/ES-2017-02-IndustrialAutomation-DCurve_LP-Destination.html

    Mike.

  • 0 in reply to mapj1

    Mike, we are feeding it through a TMD MCCB, not an MCB so I cannot select the curves

    I am trying to find in the pdf something relevant to the starting duration however there is nothing. Only the starting current.

    I dont think it would last more than 5-10 sec though

  • 0 in reply to mapj1

    Thats all I have

  • 0

    If you have Amtech plot the curves for your chosen MCCB and see how it behaves with your staring current.

    JP

  • 0 in reply to Apostolos

    OK so lets assume 150A for 5 seconds. If we consider Schneider, but if you say your preferred we can use that, then their larger TM_D units allow the thermal and magnetic parts to be set independently


    Though their  smaller sizes have the magnetic part set permanently at about ten times the thermal, which is then the single adjustable.

    something like a 25 a unit wound down to 16 or so perhaps?

  • 0

    What is the motor doing? 

    Is star delta an option, or a variable speed drive?

  • 0

    The MCCB can be adjusted to suit the thermal capacity of the cable and let the starter look after the overload.

  • 0 in reply to lyledunn

    My preferred choice of micro logic 2.2 is for distribution circuits, as it offers adjustable thermal and magnetic protection. I have also utilized the earth leakage variant when needed and the power meter option when appropriate. Also would suggest using ElectricalOM, It offers various features such as schematic diagrams, discrimination analysis, arc flash study, and CAD plan drawings

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