60-70v unregulated power supply recommendations

[Lee Roberts]

John,

What's the formula to workout what size Diodes should be used ?

I find this one intresting because surly the diodes need to be rated such that they dont negate the use of a fuse in the first instance but can also still handle what may get thrown at them?

Any clarification is appreciated.

[Clive S]

John,

What's the formula to workout what size Diodes should be used ?

I find this one intresting because surly the diodes need to be rated such that they dont negate the use of a fuse in the first instance but can also still handle what may get thrown at them?

Any clarification is appreciated.

Lee the diodes will not conduct in normal use but if the fuse does blow and the motors is decelerating it would conduct to dump the BEMF into the caps and it would only happen for a few m/secs a diode handling 1-2A would probably be ok

[john swift]

Hi Lee

Clive is correct , when a fuse blows the diode will only conduct
while the motor is generating a higher voltage than the power supplies output

just because its what I have in my spares box I would use
a 1N5408 - 1000V PIV 3A diode
( I think I used them to rectify the 250V mains )

with a 70 to 80V DC power supply a 1N5401 - PIV 100V 3A diode would be OK

John

[JoeHarris]

Hi Lee

Clive is correct , when a fuse blows the diode will only conduct
while the motor is generating a higher voltage than the power supplies output

just because its what I have in my spares box I would use
a 1N5408 - 1000V PIV 3A diode
( I think I used them to rectify the 250V mains )

with a 70 to 80V DC power supply a 1N5401 - PIV 100V 3A diode would be OK

John

How would you implement this in practice? Solder the diode across the ferrules on the cartridge (I think it would fit back into the holder)?

[john swift]

Hi Joe

I would solder the diode across the fuseholders terminals




John