Circuit Breaker Sizing
Circuit Breaker Sizing
(OP)
Hello,
I have a 30Amp 24VDC power supply. The power input to the power supply is 480VAC and the output from the power supply is 24VDC. I want to put a 3-phase circuit breaker before the power supply, but I'm having a hard time sizing the circuit breaker. Is there a formula that I can use for this? I talked to the support guys at SOLA, but he just guessed and told me that a 10A breaker would do the job, but I'd like to confirm that, plus also learn how this can be determined. Is there a formula that I can use for this?
PK
I have a 30Amp 24VDC power supply. The power input to the power supply is 480VAC and the output from the power supply is 24VDC. I want to put a 3-phase circuit breaker before the power supply, but I'm having a hard time sizing the circuit breaker. Is there a formula that I can use for this? I talked to the support guys at SOLA, but he just guessed and told me that a 10A breaker would do the job, but I'd like to confirm that, plus also learn how this can be determined. Is there a formula that I can use for this?
PK






RE: Circuit Breaker Sizing
RE: Circuit Breaker Sizing
I think that you will likely get the same answer regardless of who you ask at Sola. Sola is based in the US and here, the term "circuit breaker" traditionally is used to describe what everyone else calls an MCCB (Molded Case Circuit Breaker). In that case, there is no size smaller than 10A for a 3 phase device, if you can even find that. Most are 15A.
Elsewhere in the world you have small 3 phase DIN rail mountable "circuit breakers" with much lower ratings, i.e. 1.2A, 1.6A etc., which is what you would need as the only protective device (we would use fuses downstream from the 15A CB). We import those devices here as well, but they are not called "circuit breakers", they are referred to as "supplemental circuit protectors" because the definition for circuit breaker was already well established as an MCCB.
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RE: Circuit Breaker Sizing
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RE: Circuit Breaker Sizing
RE: Circuit Breaker Sizing
It sounds like you have a Sola/Hevi-Duty SDN-30-24-480 power supply. This is a snap-in or screw mounted DIN rail mounted power supply. If this is the case then the input current is about 2 Amps. These units are internally fused, so if you put a 10A/3P circuit breaker to protect the input conductors that is fine, but the unit itself is protected by the internal fusing.
Hope this is of help. I assume you already looked at www.solaheviduty.com ?
RE: Circuit Breaker Sizing
In North America, the minimums for field wiring would be #14 AWG and a 15 amp breaker.
respectfully
RE: Circuit Breaker Sizing