Pro/Forums - View Single Post

Since87 · 07-10-2003, 09:32 AM

There are only two issues that I see.

1. The peak current draw of each pump is likely to be 2A based on looking at the data I gathered earlier and doing some handwaving. A total current draw of 4A is pretty substantial, especially with newer systems which put much more of the load on the +12V rail. Your paralleled supplies shouldn't have a problem with this.

2. The transients may not be as well filtered by the PSU output caps with your setup. With these high frequency transients, the inductance of the cabling probably has a greater role in the transient's effect than the resistance. Depending on what you have for capacitance at the point where all of your +12V rails come together, more of the transient may go to other components (such as the motherboard) than would be the case with a typical PSU. Additional film and/or ceramic capacitors at the point where the pump cable connects to the +12V bus will make up for this. A ferrite EMI suppression core on the +12V line, between the cap/diode combination mentioned earlier, and the PSU output, would probably do an even better job of isolating the transient. EMI suppression ferrites that are easily available, may not be of much use with 3 to 4 Amps of DC current going through them though. (The ferrite might well be saturated at that level of DC current, which would make it ineffective.) It would require some research to find an appropriate ferrite core.

07-10-2003, 09:32 AM	#149
Since87 Pro/Guru - Uber Mod Join Date: Sep 2002 Location: Indiana Posts: 834	There are only two issues that I see. 1. The peak current draw of each pump is likely to be 2A based on looking at the data I gathered earlier and doing some handwaving. A total current draw of 4A is pretty substantial, especially with newer systems which put much more of the load on the +12V rail. Your paralleled supplies shouldn't have a problem with this. 2. The transients may not be as well filtered by the PSU output caps with your setup. With these high frequency transients, the inductance of the cabling probably has a greater role in the transient's effect than the resistance. Depending on what you have for capacitance at the point where all of your +12V rails come together, more of the transient may go to other components (such as the motherboard) than would be the case with a typical PSU. Additional film and/or ceramic capacitors at the point where the pump cable connects to the +12V bus will make up for this. A ferrite EMI suppression core on the +12V line, between the cap/diode combination mentioned earlier, and the PSU output, would probably do an even better job of isolating the transient. EMI suppression ferrites that are easily available, may not be of much use with 3 to 4 Amps of DC current going through them though. (The ferrite might well be saturated at that level of DC current, which would make it ineffective.) It would require some research to find an appropriate ferrite core.