can i use this rectifier? help thanks

milen007 · 15th September 2011, 04:57 PM

hi guys

i have MBR7030wt with spec 70a 30v. i am wondering if it is safe to use it to rectifier transformer secondary 0-18v to get 24vdc?

i am running it for class A amplifier that draws around 1.8a.

i have 100.000uf after the rectifier. and the loaded voltage is 23v.

i am wondering if the MBR7030wt within safe operating range?

thanks in advance
Erwin

! · 15th September 2011, 09:27 PM

Yes it is within safe operating range. The only concern would be that without much voltage margin, if your AC mains suffered a power surge, it could exceed the rectifier's rated voltage... but this is always a concern with power surges and electronic gear, it just becomes progressively more concerning as the voltage rating comes closer and closer to the transformer output voltage rating. I would go ahead and use them unless you know the AC input is subject to frequent surges.

mag · 15th September 2011, 09:56 PM

Hi Erwin,
I suppose that you are using 4 of them in brigde configuration.
In this case every diode of the bridge will see a maximum reverse voltage of
18*sqrt(2)=25.5v.
Note that the line voltage is specified at +/-15% of its rated voltage so in the worst case the diode will see 18*1.15*sqrt(2)=29.3v.

Your diode is rated 30v an a schottky diode is not at all tolerant to overvoltage.
The diode is in its rating but with a margin of only 0.7v....
I would not use this diode but use a diode rated minimum 45v of vrrm.
Btw. Why such a big diode? Why a schottky diode? You are wasting a lot of watts in running your amp in class A so why improving the efficiency of the rectifier bridge using low voltage and high current schottky?
Use a standard 25A/100V bridge and you are fine.

Ciao

-marco

stratus46 · 15th September 2011, 11:01 PM

Quote:

Originally Posted by !

Yes it is within safe operating range.
<snip>

No it isn't The diode sees twice the output voltage in reverse. He's running 48 Volts on a 30 Volt diode. It's only a matter of time.

G²

! · 15th September 2011, 11:54 PM

^ That's an interesting thought but then how do you explain those who use schottkys rated for less than double the forward voltage without having them fail?

milen007 · 16th September 2011, 05:23 AM

thanks for the inputs guys.

how bout put 2 of them in series? would it double the PIV or what the term?

erwin

15th September 2011, 04:57 PM	#1
milen007 diyAudio Member Join Date: Dec 2007	can i use this rectifier? help thanks hi guys i have MBR7030wt with spec 70a 30v. i am wondering if it is safe to use it to rectifier transformer secondary 0-18v to get 24vdc? i am running it for class A amplifier that draws around 1.8a. i have 100.000uf after the rectifier. and the loaded voltage is 23v. i am wondering if the MBR7030wt within safe operating range? thanks in advance Erwin

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15th September 2011, 09:27 PM	#2
! diyAudio Member Join Date: Jun 2005 Location: Midwest	Yes it is within safe operating range. The only concern would be that without much voltage margin, if your AC mains suffered a power surge, it could exceed the rectifier's rated voltage... but this is always a concern with power surges and electronic gear, it just becomes progressively more concerning as the voltage rating comes closer and closer to the transformer output voltage rating. I would go ahead and use them unless you know the AC input is subject to frequent surges.

15th September 2011, 09:56 PM	#3
mag diyAudio Member Join Date: Jan 2008 Location: Chiasso	Hi Erwin, I suppose that you are using 4 of them in brigde configuration. In this case every diode of the bridge will see a maximum reverse voltage of 18sqrt(2)=25.5v. Note that the line voltage is specified at +/-15% of its rated voltage so in the worst case the diode will see 181.15*sqrt(2)=29.3v. Your diode is rated 30v an a schottky diode is not at all tolerant to overvoltage. The diode is in its rating but with a margin of only 0.7v.... I would not use this diode but use a diode rated minimum 45v of vrrm. Btw. Why such a big diode? Why a schottky diode? You are wasting a lot of watts in running your amp in class A so why improving the efficiency of the rectifier bridge using low voltage and high current schottky? Use a standard 25A/100V bridge and you are fine. Ciao -marco

15th September 2011, 11:54 PM	#5
! diyAudio Member Join Date: Jun 2005 Location: Midwest	^ That's an interesting thought but then how do you explain those who use schottkys rated for less than double the forward voltage without having them fail?

16th September 2011, 05:23 AM	#6
milen007 diyAudio Member Join Date: Dec 2007	thanks for the inputs guys. how bout put 2 of them in series? would it double the PIV or what the term? erwin

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