| Electronics > Projects, Designs, and Technical Stuff |
| AC-DC 340v power supply board design help |
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| blazini36:
I use an unconventional 2200w AC servo drive on my CNC milling machine, it's unconventional in the way that it does not have it's own DC power supply. All that is really necessary and what I have done in the past is use a bridge rectifier fed from 120v or 240v mains and push it through a few filter caps. This works fine as far as supplying power but it has the issue of high inrush current that will pop 10amp fuses immediately if the filter caps (I used 4 x 470uf). I wanted to consolidate this to a single PCB and resolve this inrush issue but I'm having a bit of trouble with it. I worked up a schematic just to put it on paper but I'd like some thoughts and suggestions before I put much more brain power into it. At the moment I'm trying to figure out what value and power rating R2 should be, the shunt value, and I'll likely need a diode and some passives between the output of the INA138 and the IGBT. Wasn't sure whether to go with an IGBT or a mosfet for Q1 but I slapped the IGBT in there for the moment. The idea there is that the voltage from the shunt should have the output from the INA138 operate the gate of the Q1. The Q1 should bypass the current limiting resistor R2: Just a schematic to show what I'm thinking. Open to advice or being told I'm doing it completely wrong: |
| NiHaoMike:
Put a NTC in series with the input and bypass it with a contactor. Simple and just works. |
| blazini36:
--- Quote from: NiHaoMike on January 19, 2020, 01:44:27 am ---Put a NTC in series with the input and bypass it with a contactor. Simple and just works. --- End quote --- Thought of this but I have not seen an NTC above 180w and I don't want to use an off board contactor (keeping it all on board is the whole point). I haven't seen a small PCB mount mechanical relay that can handle 30amps and 300v. I need to rate the components at about 30amps since if using a lower input voltage the current will be much higher, also need to maintain the abillity to use 240v on the input side for a 340v output. |
| Prehistoricman:
Perhaps you could use a triac + diac dimmer circuit to slowly raise the input voltage. --- Quote from: blazini36 on January 19, 2020, 02:17:31 am ---Thought of this but I have not seen an NTC above 180w and I don't want to use an off board contactor (keeping it all on board is the whole point). --- End quote --- You're probably looking in the wrong component category: digikey link to inrush current limiters |
| Yansi:
--- Quote from: blazini36 on January 19, 2020, 01:26:07 am ---...it's unconventional in the way that it does not have it's own DC power supply... --- End quote --- Incorrect. It is actually pretty conventional, for a servo driver to NOT have its own DC supply. This way multiple servo controllers can share the same DC bus, so if one of them is regeneratively braking (which for a servo driver is pretty common task), other servo driver can consume the energy, instead of dissipating it into a brake resistor. You have probably meant inconvenient ("pain in the arse to use"), not unconventional ( i.e. "not standard"). |
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