Hey guys, thanks for the helpful community.

BLUF: Is in-rush current primarily determined by the internal component design of a piece of equipment or by the external power supply to it (or more specifically, the total power draw of the other components on the power supply)?

I am working on a project re-designing an existing cabinet to from 460 V input in the previous model to 120 V input in the current model. In order to accommodate the lower input voltage, we changed the protective fuses accordingly. These fuses have been blowing intermittently which we have determined the likely cause to be high in-rush current to the system upon initial power on.

This new cabinet is currently installed in a test facility that doesn't exactly match its intended long term tactical use (those facilities are not built yet). The components in the tactical use system have been sort of consolidated onto fewer power supply buses, so the cabinet I am working on will have different different components (and thus a different impedance profile) when finally installed in its intended tactical setting.

We are trying to determine if the primary cause of the in-rush current we are seeing is a result of the cabinet design itself (in which case a design change on the fuses, to a slow-blow type, would be warranted) or if the primary cause is the power supply and other components on this system resulting in a surge larger than otherwise would be present (in which case a reconfiguring of the facility power supplies would be warranted).

So I am hopeful someone can help me understand the primary driver of in-rush current: is it mostly related to the equipment design itself? Or is the power supply/other components being supplied more of a factor?

Thank you for your time!

 

Hey guys, thanks for the helpful community.

BLUF: Is in-rush current primarily determined by the internal component design of a piece of equipment or by the external power supply to it (or more specifically, the total power draw of the other components on the power supply)?

I am working on a project re-designing an existing cabinet to from 460 V input in the previous model to 120 V input in the current model. In order to accommodate the lower input voltage, we changed the protective fuses accordingly. These fuses have been blowing intermittently which we have determined the likely cause to be high in-rush current to the system upon initial power on.

This new cabinet is currently installed in a test facility that doesn't exactly match its intended long term tactical use (those facilities are not built yet). The components in the tactical use system have been sort of consolidated onto fewer power supply buses, so the cabinet I am working on will have different different components (and thus a different impedance profile) when finally installed in its intended tactical setting.

We are trying to determine if the primary cause of the in-rush current we are seeing is a result of the cabinet design itself (in which case a design change on the fuses, to a slow-blow type, would be warranted) or if the primary cause is the power supply and other components on this system resulting in a surge larger than otherwise would be present (in which case a reconfiguring of the facility power supplies would be warranted).

So I am hopeful someone can help me understand the primary driver of in-rush current: is it mostly related to the equipment design itself? Or is the power supply/other components being supplied more of a factor?

Thank you for your time!

There are far too many unknowns and unspecified devices in your system for me to even make a wild guess at the cause. Can you be a lot more specific? Have you made any measurements to determine the amplitude and source of the inrush currents?

 

There are far too many unknowns and unspecified devices in your system for me to even make a wild guess at the cause. Can you be a lot more specific? Have you made any measurements to determine the amplitude and source of the inrush currents?

No sorry I am not able to provide the design details.

I intended my question, however, to be more general vs. this design specific on what tends to be the primary driver of in-rush current--the component or the system. If I run two tests, and instrument to measure the in-rush: one with just my cabinet on a power supply with no the components, and then again with 3-4 added components on the same power supply. Should I expect to see a difference in the in-rush current to my component? Or would it likely vary to a large degree with the introduction of the other components?

 

I have no idea. It would depend on the circuitry of the power supply and what the components are.