IEC conductor and breaker for motor
IEC conductor and breaker for motor
(OP)
I am not able to find the rules to size the conductor and breaker for a motor using IEC standards. (In NEC you simply take 1.25 times the FLA); I will appreciate if someone helps me in sizing IEC conductor and breaker for the motor.






RE: IEC conductor and breaker for motor
Be careful if the manufacturer has type-tested the contactor you want to use with (say) a 100A frame size breaker and you are using a 160A frame size because of the higher fault rating available with the bigger breaker: the higher energy let-through may force you to choose a larger contactor to just to maintain a type-tested combination. You need to ask for type 2 coordination; type 1 coordination allows a fault to be cleared but permits the contactor and overload relay to be destroyed in the process.
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If we learn from our mistakes I'm getting a great education!
RE: IEC conductor and breaker for motor
If I size the conductor for 300A, it will not provide any allowance for the motor starting current. (In NEC, if the FLA is 297A, then the conductor is sized for 297*1.25=371.25A.)
RE: IEC conductor and breaker for motor
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If we learn from our mistakes I'm getting a great education!
RE: IEC conductor and breaker for motor
RE: IEC conductor and breaker for motor
It is my understanding that the current given in the starter is the "Rated Opeartional Current" (Ie)which is not necessarily to be the motor FLC.If you select your contactor from the manufacturer's table according to the motor kW rating,voltage and Type 2(or 1)coordination, then you are covered.Also the manufacturer's tables are available to select the rating and type of either the MCCB or fuse depending on your wish based on Type 1 or 2 coordination.Per IEC, you cannot use the MCCB(fuse) from one manufacturer and the contactor from another manufacturer,because it will violate the Type 2(or 1) coordination.The sizing of the motor cable for its continuous current and short circuit rating should be done per IEC 600364 or your local code.
RE: IEC conductor and breaker for motor
I wasn't really trying to relate the AC-1 rating to motor starting, just to say that the motor starting current is accounted for within the AC-3 rating, which is part of the reason why for any given contactor the AC-3 rating is considerably lower than the AC-1 rating.
A qualifier to Kiri's post: some manufacturers with complementary ranges of products have type-tested together: for example A-B have type-tested their contactors and O/L relays with Terasaki's breakers. A-B's IEC breaker range isn't that good, and Terasaki don't make contactors, hence the mutually beneficial relationship.
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If we learn from our mistakes I'm getting a great education!