Another benifit I remember for 3 phase power is that it creates a rotating magnetic field inside of motors by having 3 windings. This is good for starting a motor and setting its direction of rotation. Using single phase power, motors have to use some form of phase shifter to do the same thing. Also with 3 phase power, the total power is distributed over three wires instead of one or two, and therefore smaller wire is needed.
Bill and Jojo, I just happened to glance at the chat before logging out.
I was involved with aircraft work years ago. My instructors like to point out that 400Hz, 3 phase power was nearly DC when it came out of the rectifier. Smaller filter caps, redundant power supply if 1 phase fails were tsome of the benifits.
Bill: I'm not a power guy, but I would like to understand better the rational why 3-phase is more efficient than single phase. Is it because the load can be distributed better in 3-phase while single phase takes all the brunt?
MPEDRAZA--you may nbot need digital--but if you want to capture, retain, an dfurther analyze, you will. Question really is at what point in the signal chain to you go digital: at the front end, or further along the chain, after the analog calculation?
Davec3000: those ICs can be good options, yes. But you still have to think about what you are trying to measure. It's like using an "average": usually a good thing, but by definition, "average" obscures detaisl--and that may be very good, or very bad, for the situation.
Yes Bill, analog can be a simple solution. I tend to try compressing most operations into a uC with analog front-end to condition or pre-process. That would be the hybrid approach you mention. Hardware reuse is easier for me when a uC is used instead of a dedicated circuit.
Using Digital due to calculation and accuracy requirements -- better than 1% -- so using TI MSP43047197 SOC -- since it has 14 Bit ADC etc. Regulatory approval -- so not much choice for cumulative energy use. Complicated -- but that's the answer.
@bicyclebill: Second bullet on slide 3 suggests that 12 bits resolution (1 part in 4096) are required to digitize an analog value to 1% full scale. Is that what is meant? If it is, why not 7 bits (1 part in 128, which is approximately 1%)?
I'd like to see a poll: when checking failed fuses, is it acceptable to DVM across the fuse verses to earth/ground/common? I check to E/G/C, but the topic can bring heated discussions! (Temps here are expected to drop 25+ in 45 minutes or less!) :)
Your slides mention 12Bit accuracy for measurement. I am currently testing TI MSP430F57197 (SOC) for 3 Phase -- it has 7 X 16 Bit Ganged (simultaneous reading) ADC -- others in this lne have up to 24 bit ADC -- fwiw -- I have not checked other lines.
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