Doubt regarding stepper motor current rating

[wassupcrew]

What type of stepper motor drivers are you using?

routout cnc

[James Newton]

Not the brand, the type... e.g. Bipolar, Unipolar, and you also need to think about the mode, Full step, half step, microstep... It's different for each. The page at:
techref.massmind.org/techref/io/stepper/power.htm runs down all the options and is kept up to date.

Worst case: You need double the rated current per motor. So for a 2 amp motor, supply 4 amps, and for 4 of those, a total of 16 amps. Depending on the driver and mode, you may need as little as 8 amps... but then you will need a higher voltage and you will NOT get the full torque possible.

[wassupcrew]

ok got it now. 2amp motors running in bipolar series mode in 1/8 microstep mode. if i get a 15 amp psu that should work alot better than the 4.2amp i have at the moment

[RomanLini]

No that's not correct!

We need to know the type of *operation* of your drivers. According to the routoutcnc.com website;
Single Driver

Their 3amp stepper motor drivers are "PWM" type which means they are a chopper driver, which is common on most 3amp stepper driver chips.

As a chopper drive it should run about 0.6 times the stepper current, so 4x 2amp motors = 8A x 0.6 = about a 5amp power supply is needed to get absolute peak performance from your motors.

Your 4.2amp PSU is probably quite acceptable if you are not running extremely high speeds or high rapid accelerations. As a simple test you can connect a 10amp ammeter (or multimeter with 10 amp range) between your PSU and your drivers, and display how much current they actually need in use. I would be surprised if it draws more than 2 or 3 amps in most normal cutting and moving tasks.

[wassupcrew]

thats great roman thanks alot. will be upgrading soon though so will be back for more info when i get the new drivers an bob