Do I need over current protection?

[mjbarcelona]

Hi guys, i'm working on some project, do i still need over current protection if i'm using a soft starter and do I still need circuit breaker for that motor???

 

[telectrix]

if it is a fixed load, you could dispense with overload protection, but still need fault (short circuit) protection

 

[Deleted account]

if it is a fixed load, you could dispense with overload protection, but still need fault (short circuit) protection

I understand with a fixed load there is no chance of overload, but surely the short circuit protection will automatically give overload protection anyway even if it doesn’t need it.
Am I missing something?

 

[telectrix]

I understand with a fixed load there is no chance of overload, but surely the short circuit protection will automatically give overload protection anyway even if it doesn’t need it.
Am I missing something?

no.you could have. say, a 2.5mm cable (27A CCC) protected by a 50A MCB giving fault protection, but the 50A MCB will not provide overload protection to the cable.

 

[Baddegg]

Was pondering that myself....good explanation @telectrix

 

[netblindpaul]

Upstream of the soft start, yes, downstream, no the soft start should be programmed to limit the overload current, if not the soft start instructions must give you the data you need.
Just remember if it's machinery BS7671 is irrelevant.

 

[littlespark]

OP isn’t in UK? (Correct me if I’m wrong) So BS7671 is irrelevant anyway.

 

[netblindpaul]

OP isn’t in UK? (Correct me if I’m wrong) So BS7671 is irrelevant anyway.

You're right, I saw the flag under his name and saw the little Union Jack and thought it was the whole flag, not just the small bit in the corner!
IEC 60364 still applies in AUS/NZ though it is a local interpretation like 7671, as would IEC 60204-1 which isn't so local.

 

[Megawatt]

Hi guys, i'm working on some project, do i still need over current protection if i'm using a soft starter and do I still need circuit breaker for that motor???

The soft start should have your overloads built in it you just have to read the manual and set to probably 115% X the full load of the motor and YES you have to have a circuit breaker for the soft start and motor

 

[SheffSimon]

Overload should be set to motor FLC. Job done.