For my servo CNC lathe conversion, I bought a linear power supply with a toroidal transformer from AnTek.
http://www.antekinc.com They're a little pricy, but nothing like the prices I've seen in this thread. The AnTek power supplies provide the higher voltage needed for the stepper or servo motors, but also supply 24VDC for the control voltage and 5VDC for the logic level electronics on the machine side of the optical isolation barrier, so they're actually three power supplies in one. You can sometimes get a switching power supply with 24 and 5 volts combined, but I don't remember ever seeing all three voltages in a switching power supply. I also don't remember a switching supply with a higher motor voltage and 24VDC for a control voltage, but someone probably makes one. Those AnTek supplies cost a little bit more than the equivalent combination of imported linear power supplies, but you can see where the money went. They're very high quality. AnTek also sells just the toroidal transformer if you'd like to make your own linear power supply. The transformers are relatively cheap, and it's easy to add a bridge rectifier, some big filter capacitors, and a breaker on the output. AnTek has an online price sheet, which I love. For my stepper CNC milling machine conversion, I bought a package deal that included a parallel port breakout board, three 1600 ounce inch stepper motors (yowza!), three stepper motor drivers, and three 60V switching power supplies. The motors pull so much current that they each have their own power supply. Switching power supplies usually don't have much reserve current capacity (small capacitors). They can suffer from voltage sag when called upon to supply high inrush current to inductive devices like motors, which is the entire point of using higher voltage power supplies and motor controllers that limit the current to a safe value. With a large capacitor on the output of the switching power supply to provide instantaneous current, servo motors may be able to accelerate faster, and stepper motors accelerate faster and run faster. If you want to eliminate the high frequency noise from a switching power supply, you could use ferrite beads on the output of the switching power supply, or wrap that output wire several times around a ferrite toroid core to act as an RF choke. Linear power supplies typically have large filter capacitors because they need to have minimal ripple voltage when fed full wave rectified 50 or 60 Hz power (with rectified power pulses at 100 or 120 Hz). For motors, we don't mind a drop of a few volts for high instantaneous power requirements. Typically, linear power supplies have noise at twice the AC line frequency, and switching power supplies have noise at the switching frequency which is typically thousands of Hz. Neither noise is a particular problem for the motors, but can reek havoc with the control electronics. Shield the cables, ground one side of the shield at the power supply side, and don't run the motor wires next to the limit switch or encoder wires and you'll probably be OK. If you can run a differential signal for the encoder, you're almost certain to avoid noise problems on the encoder signals. ------------------------------------------------------------------------------ Monitor your physical, virtual and cloud infrastructure from a single web console. Get in-depth insight into apps, servers, databases, vmware, SAP, cloud infrastructure, etc. Download 30-day Free Trial. Pricing starts from $795 for 25 servers or applications! http://p.sf.net/sfu/zoho_dev2dev_nov _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
