I already have the stepper and drives and I'm not sure about the PSU current and voltage.
My four steppers (chinese) have the following specs (if real): nema34, 66mm length, 4A, 0.6Ω, 1.6mH and the drives (chosen to fit my budget) are based on the THB6064 chip: 4.5 A absolute; 4.0 A operating range; 50V absolute maximum; 42-45V? operating.
The toroidal transformer will be manufactured to my specs.
How about two sec. windings at 33V and a total of 630 or 750VA?
Why two windings... I will most probably upgrade the drives to 80V in the future and it will be nice to be able to reuse the toroid.
I also want to build a B/C head or a rotary axis soon and to be powered from the same PSU.
Any help will be greatly appreciated
I bought mine here;
Chassis mounting toroidal transformers
Two 33v windings in series will give you 66 * 1.414 = 93v DC which is too much.
A 625VA 2x24 would be better, this would give approx 34v dc in parallel, 68v dc in series
Standard Range Toroidal Transformers: CM0625224: 625VA 230v to 2x24v
Why Nema34 and not 23s?
33v secondary will give 43 to 48v on supply variation which doesn't leave much room for regenerative dumping on a 50v drive. I'd go for 30v secondary.
Don't see how you'd reuse the toroid on an 80v drive. 2*33*1.414-1=92v +/- 5%, you need 2 x 27v secondaries for maximizing an 80v drive.
When I'll need to reuse the toroid for 80V I'll take out some wire from the secondary.
Not sure about the voltage drop on load. Will it be significant?
Best of luck will all of that.
I've read and remembered this rule somewhere on the CNCZone (I think): "Never apply voltage that is greater than 32 times the square root of the motor inductance in mH.
BTW, where do you get the 6064 drivers from? I am looking for the chips only but without success.
Probably I'm wrong with my nema34 steppers but I've seen a lot of different Chinese specs and I do not trust them, and the ones sold in Europe and USA have the same Chinese specs sheet... and they are so optimistic compared to the good brands.
The 3.1Nm has too high inductance for my 42V drives.
I have missed the rotor inertia 560g·cm2 vs. 850g·cm2. High speeds without good acceleration are worthless. Will see them performing in real life... to many calculations for a hobby engineer.
Any recommendation regarding the PSU power? I have read somewhere that 60% of the steppers/drives current is enough for a toroid. Is this true?
And another probably dumb question.. with 25A at 30V AC will I have 25A or 18A at 42V DC?
THB6064 drive kit
Last edited by paulus.v; 29-10-2013 at 12:21 AM.
25A @ 30V AC will give you 25A @ 42V DC
Last edited by irving2008; 29-10-2013 at 06:09 AM.
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