[Tutu]

I built a PSU with a toroidal transformer, dual input 115v, dual output 50v, wired in series on the input and parallel on the ouput.

See attachments for what I did, I have an usually high input voltage from the grid it fluctuates but today I was getting 250v in which gave me 78.2v out on my toroidal transformer build.

I have AM882's and I think I may have already blown one up (At least it doesn't work and I've bought a new one) so do not want to damage them.

Will I be ok with this voltage, I am in the UK so should be getting ~240v.

[Jim Dawson]

If your voltage is consistently high, you could take a few turns off of the secondary and reduce the output voltage. Not sure how many you would need to take off, but you can measure the input voltage and the output AC voltage and calculate the Turns Ratio TR = ACVin/ACVout. DCVout = ACVout * 1.414 From this you could figure out how many turns to remove to get you desired max DCV out.

[ger21]

I've heard that Leadshine's aren't too tolerant of opervoltage, so 78V may be a bit risky.

[john-100]

whats the spec for the transformer

the 50V output is when the transformer is fully loaded
off load ( depending on the transformers size ) is likely to be 2 or 3 % higher
[small 10VA transformers can be 10% higher]

in my part of the UK , during the day , the main voltage voltage varies between 243 V & 248V

so I would have to increase the expected 71V DC (50 x 1.4142) by 11% ( 248/230 x 1.03 = 1.11)

the resulting DC output will be about 79V off load which is at the upper limit for the AM882 drivers

the added problem is the returned energy
when a moving part of your machine is rapidly decelerated and drives the motors round , turning them into electrical generators

this added current will increase the stepper drivers DC supply voltage !
possibly enough to destroy your stepper drivers

( some systems have a returned energy dump to automatically add a high current load to the power supply to limit the maximum voltage due to any returned energy )

it looks like you need a 45V transformer which will give you about 70V DC


John