Power supply current rating

I'm in a bit of a quandary when it comes to the Current capability of the power supply to run my 3 steppers on my converted bench mill
X and Y axis use 1605 Ballscrews with a 2:1 pulley drive and Y axis uses a 2.4:1 pulley drive (no ballscrew)
Maybe someone can help.

I have two power packs available.

24Vdc 10Amps
48Vdc 5 Amps

Given that I'm about to run a bench mill with 3 of the steppers of the specification below. Which power supply would be better suited ?

Model Voltage(V) Current /phase(A) Holding Torque(Nm) Inductance /phase(mH)
M60STH100-4004S 2.8 4.0 4 3

Please excuse if this is posted to the wrong area or forum.

Many thanks

George

If I'm reading it right you have 4.0 amp steppers with inductance of 3.
Using the ever popular gecko rules,
for stepper voltage (square root of the inductance times 32) we get 55 volts would be ideal to run these steppers at.
for power supply current (total of steppers amps times .6) we get 4+4+4=12 times .6 = 7.2 amps.
So neither supply is ideal.
A better solution would be a 48 volt 10 amp supply for more headroom, plenty available on ebay.
Gun to my head I would use the 48v 5a supply for the x and y and the 24v 10a supply for the z.
I'd want the x and y to have the better speed from the 48 volts.
Hoss

Thanks Hoss, no room inside my box for two supplies but I know where you are heading.

I managed to find a 48VDc at 8 Amps. so that may do for now.

Thanks

George

Yeah, one supply would be better so that should do, I ran (3) 5 amp steppers on one 48v 7.3 amp power supply with no perceptible problems.
Hoss

Hi,

voltage primarily depends on the stepper drivers you use. Voltage should be as high as possible (within the drivers specification) because voltage is responsible for acceleration and maximum feed.
Current depends on the motor - 5A is a little scarce for three 4A motors - but it may work.

So: if your stepper drivers accept 48V get a 48V supply - if they accept 80V get an 80V supply.
You can try 5A if it has short circuit and thermal protection - if it shuts down just get a second one and supply 2 motors with the first and the 3rd with the second.

Christian

Thanks Christian.

Understood.

Quote:

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Originally Posted by Christian Knüll

Hi,

voltage primarily depends on the stepper drivers you use. Voltage should be as high as possible (within the drivers specification) because voltage is responsible for acceleration and maximum feed.
Current depends on the motor - 5A is a little scarce for three 4A motors - but it may work.

So: if your stepper drivers accept 48V get a 48V supply - if they accept 80V get an 80V supply.
You can try 5A if it has short circuit and thermal protection - if it shuts down just get a second one and supply 2 motors with the first and the 3rd with the second.

Christian

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Actually, that's not really correct.... The "optimal" voltage is a function of the inductance of the particular motor, not the driver. If the voltage limit of the driver is below the ideal voltage, then the lower voltage must be used, and performance WILL be reduced. The power supply only needs to be rated for 67% of the rated motor current, so a 3A motor will work fine on a 2A supply. Current mostly determines motor torque, and voltage largely determines maximum speed, because lower than ideal voltage prevents the motor from ever reaching rated current at higher speeds, so torque falls off. Increasing voltage beyond the ideal value for a particular motor has absolutely no benefit, and will cause the motor to run much hotter than it would if used at its ideal voltage.

Regards,
Ray L.

Thank you Ray

Best regards

George