Thread: running steppers at destruction volts and amps

You have to be an engineer. Every engineer I know has this instinctive urge to test to destruction.
If you are after speed and torque then bypass steppers and go to servos.

nar just a chippy , but still like to push it as far as i can , and then back track a wee bit the dodgiest engineering way
bypass steppers and go for servos but then i wouldn't know how far "not" to push a stepper

woops the peltiers are 130watt , so 12 x 130's , 1500 watts of cooling ? might use it for a room aircon after

Originally Posted by SawDustSniffer

but then i wouldn't know how far "not" to push a stepper

woops the peltiers are 130watt , so 12 x 130's , 1500 watts of cooling ? might use it for a room aircon after

And miss all that fun

Could do with the peltiers here at the moment - hot, humid and cyclone coming down the coast. You are probably used to it but it ain't pleasant for us softies down here.

yer good luck with that , darwin has the most expensive houses in Australia because of the odd sea breeze that comes in , Perth is not built for a cat1 cyclone , i hope its only a cat1 when it hits , a cat 2-3 would be nasty ( good excuse for a up ,up here at cat 1-3 , cat 4-5 we hide )

tip
put all your photo's ,paper work , electrical stuff in garbage bags ,and tape the opening shut , and store them in the smallest room in the house ( toilet) , bag opening pointing down , at 140km/h winds your roof might hold , but if it gets hit by anything ( debris, the dodgy built carport 3 doors down ) you might loose your roof , x tape all your windows ( 1/2 the thickness and twice the size windows in perth ), 3 days of tins and water , battery radio , ( the eye can fool you ) , first aid kit ,torch and the mandatory 2 cartons

always a good idea to shelter in the smallest room as well , not because its the strongest , just handy when you S#!+ your self

under ground carparks are good , but might flood in perth , darwins have backup genie's and huge pumps , so we can use them as shelters

good luck , ken

Originally Posted by SawDustSniffer

always a good idea to shelter in the smallest room as well , not because its the strongest , just handy when you #### your self

good luck , ken

Like your style.

Not worried as Julia will bail us out with a new tax if it goes pear shaped. Not knocking the poor buggars that copped the floods but good for one good for all.

i hate idel chat on frorums but here go's ,

dont drink beer outside until its too bad to stand

the ninja stars will get you ,

the 4 nail pressed disk that holds down shade cloth , a strong gust of wind will come , and you will have the air full of ninja stars ,

safety glasses , a heap of rope , battery drill , and a selection of the biggest screws you can find , comes in handy

found a faulty stepper to make magic smoke with

looks to be a 8 wire nema34 600-800 oz inch , no names or details on it

runs rough i was told

first up i pulled it apart to find out what amps this motor can take , the enameled wire is 0.8mm dia , a look in a wire size book says its "AWA 20 " and can take a max amps of 2amps

looking at the wiring the two coils at 90 deg to each other are wired up together , 1-3 , 4-6 , 5-7 , 8-2 , so paring up the opposite it will run under a 4 wire driver so 1-3 & 5 -7 wired up in parallel will have 1.8ohm
wired up in series it will have 3.6ohm

also the rotors at 90deg are 180deg out of sink , i checked the wiring and yes the 2 coils are wound in opposite directions , so one is north the other is south on each pair of coils ( pic 1 )

while i was working out what colour wire is connected to what coil i found coil 7 wire had a resistance of 42ohm , wire to 3 was 8ohm , rest were 2 ohm ( the wire its self ) there's the fault , broken external wires

so now ill rewire the contacts for a 4 wire setup ( and get rid of the broken wire ) , glue in a temperature sensor in between the coils and put it back together

one thing i did not expect is the staggering of the internal magnet notches ??? buggered if i know why ??? pic 2 , 200 real steps instead of 50??

looking around on the web and i found a way of calculating the motors inductance


L = 0.394r^2 X N^2 / ( 9r + 10len )

where:
L = inductance in uH
r = coil radius in centimetres
N = number of turns
len = length of the coil in centimetres

the coil size of the motor is 72mm x 12mm x 9mm high (center of copper bundles )

at AWA 20 the wire has a resistance of 10.153ohms per 1000feet ,
1.8ohm for 2 coils = 0.9ohm per coil ,
10.153/0.9 = 11.281 , ohms per 1000foot / ohms of coil
1000/11.281 = 88.64feet of wire
88.64feet = 27.017meters of wire on each coil


with the coil size of 72mm x 12mm , the circumference = 168mm
27.017M / 168mm = 160 turns to use up 27meters of wire

this formula is for a round coil but this one is rectangle ??? ner enough,
2pi*r is the circumference so 6.28 * r = 168
168 / 6.28 = radius of 26.75mm


back to inductance
L = 0.394r^2 X N^2 / ( 9r + 10len )

where:
L = inductance in uH
r = coil radius in centimetres
N = number of turns
len = length of the coil in centimetres

so inductance = 0.394*(2.675*2.675) * (160 *160) / ( (9*2.675)+(10*0.9)
= 0.394 * 7.1556 * 25600 / ( 24.075 + 9)
inductance = 2182uH per coil
ill be wiring 4 coils together so 8728uH

noted this formula off another web site
Formula for best/max psu voltage is 32 times the square root of the inductance
uH to mH is 1000 , so 8728uH = 8.728mH
32 x squ 8.728
94volts to get the best quality magic smoke to come out of the stepper

to stop the magic smoke coming out of the PSU another formular comes in
Your filter capacitor on your power supply is determined by your power supply voltage and current.(80,000 * I) / V = C
80,000 * 2 / 94 = uF
1700uF capaciter between the driver and the PSU ( switchmode)


sorry for posting my workings out , but some one might use it ???



so the first setup will be just under 2amp , 90volts , and use a tension wrench to measure the hold torque , and an RPM for max unloaded speed
wired in series and parallel tests

then add some peltier's with heat sinks to cool the motor and test again

ill have a temperature censer in between the coils , when it gets to 120c a thermostat will kill the power too the power supply unit , the wire can handle 200c before melt down of the enamel , so there shouldnt be any magic smoke

then ill rewire the stepper with 4 amp wire , then 8amp wire , and see if the torque and speed change much , it looks as if i can get twice the amount of wire on the coils than the stock windings

from what ive seen on other sites , the more the volts , the faster it spins , the more the amps the more torque ,
the higher the amp wire ( thicker ) the less turns fit in the coil , the less volts can be used , so speed kills torque , and torque kills speed
with the extra room on the coils i think i can get 4amp wire with the same 160 turns on the coils