Power supply calculations???

[stuart76]

Hi guys, Im electroically illiterate so I was wondering if anyone could confirm or correct my thoughts.

Im building a 4 axis mini mill. I have 4 stepper motors (1.8 volts - 3 amps - 6wire). Ill be running 12 volts into the motors.

If 3 amp means 3 amps per phase then thats 6 amps per motor, times 4 motors so will i need a power supply that can supply more than 24 amps? (seems alot). Ive also been told to go for 1 power supply rater than multiple supplys due to common earth voltage variation??? Its alot cheaper to buy a few small amp supplys than 1 big one. thanks.

[OCNC]

Originally Posted by stuart76 Hi guys, Im electroically illiterate so I was wondering if anyone could confirm or correct my thoughts. Im building a 4 axis mini mill. I have 4 stepper motors (1.8 volts - 3 amps - 6wire). Ill be running 12 volts into the motors. If 3 amp means 3 amps per phase then thats 6 amps per motor, times 4 motors so will i need a power supply that can supply more than 24 amps? (seems alot). Ive also been told to go for 1 power supply rater than multiple supplys due to common earth voltage variation??? Its alot cheaper to buy a few small amp supplys than 1 big one. thanks.

I think the way you figure it in your example is 3 amps per motor as only one phase is active at any moment so that would give a requirement of 12 amps. Also less current is drawn with less loading so how close you will be to full load over what period of time becomes a factor. Linear power supplies can typically be overdrawn for short periods of time without being damaged. The intermittent collapsing back EMF of the steppers also adds to the conservation of power.

Chris

[2muchstuff]

If you are using a driver that has a pulse width modulated output (Gecko) your current usage will be 2/3 rds of your motors nameplate rating. This is due to the power going to the motor being pulsed.

[H500]

Your power supply selection will depend on your choice of controllers. If it's one that uses power resistors to limit the current, then you do need 24 amps for 4 motors. Most controllers drive 2 coils simultaneously.

You should really avoid this type of drive since the power resistors and bigger power supply will end up costing as much as a chopper drive, which gives you much better performance.