On Fri, 2012-03-02 at 13:17 -0800, Karl Cunningham wrote: ... snip > What DC bus voltage are you planning to feed to the IRAMS module?
I have a 45 Volt motor to start testing with. I 'll probably start at 30 to 50 Volts depending on what supply I can scrounge up, then go up from there. I would like to go up to 240 Volts. > I > would think a low-ESR capacitor of 1 or 2 microfarad would be desirable > across the DC bus, located right next to the IRAMS module. A low-ESR > film capacitor should work about as well as a ceramic and may be > easier/cheaper to find if the voltage is very high. That's what the datasheet seems to recommend except they recommend both the ceramic and electrolytic caps together. > Motor input caps? Are these the 2.2uF caps in your schematic? No, I meant the motor power supply caps. > I think > these are bootstrap capacitors, used to generate a voltage inside the > chip to drive the gates of the top switches. > Have a look here: http://www.irf.com/technical-info/designtp/dt04-4.pdf > > Their minimum capacitance depends on how much voltage you have on your > DC bus, what your switching frequency is going to be, and what minimum > duty cycle you plan to have. Are any of these things known? Not really, but the datasheet recommends 2.2 uF above something like 12 kHz, so the plan is for 2.2 uF. It seems these can be fairly low voltage. I'll probably go for 50 Volt electrolytic caps. > Grounding is key to using these modules. Especially at high voltage. For > breadboarding, try to do it on a board with a copper plane. Without > this, it's not hard to get switching spikes across ground lines which > are large enough to turn a logic 1 into a logic 0. When that happens, > things can go bang very quickly. > > Karl I don't have my PC board machining setup done, or even started. I guess ordering parts might have been a little premature. I'll either need to order prototype boards from BatchPCB or finish my engraving spindle first. I got the IRAMS module in today, it's cute, I'm having a hard time believing I can run a 1/2 to 1 HP motor with it. After poking around Digikey some more, I noticed there is a 4 HP module available, I want it. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
