dual at supplies in series

[dertsap]

i understand a lot of guys are running 2 or more at/pc supplies in series , i just started running dual supplies for 24v and plan to run 3 for 36v , a couple of guys i know are quite knowledgable about electronics and they say that i am destined for trouble ,because something will probably short out and blow something possibly my motors or board , so has anyone had any problems or know of any problems that i should be aware of , ive come too far to blow it up now , any positive or negative input would be greately appreciated

[jeffs555]

As long as the wiring is good, and the motors, drives, and power supplies are operated within their ratings, nothing should short out. You do need to make sure that the PC supplies have the internal grounds properly isolated.

However, many of the less expensive drives have voltage ratings around 30 to 40 volts, and might blow if used at 36 volts. You do need to make sure you have a large value capacitor connected right at the drives. Without this capacitor, the back emf from the motors can generate voltages much higher than the power supply voltage. This can blow the drives even if the power supply is less than the rated voltage of the drives. The capacitor reduces but does not completely eliminate the voltage spikes so you don't want a supply too close to the rated voltage of your drives.

[NC Cams]

Recall that PC power supplies are switchers for COMPUTERS and they generally did not see the sort of loads that a PWM type servo/stepper drive might generate. A large amount of capacitance is very helpful in storiing the endergy reserve needed for fast motor accelerations/responce in a CNC environment.

Will AT P/S's supply the volage and current??? Yes BUT with the proper ancillary support from capacitors providing grounding and sizing are otherwise appropriate.

Then again, some of them are so cheap in surplus that it won't cost that much to learn what not do do via the "smoke" method. BE CAREFUL!!!!!