@rswanson, good memory. 400Hz power also made the soldering iron get even hotter! The patrol aircraft I worked on at the time had outlets for appliances and test equipment.
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?
@rswanson: MSP430 is a large family of TI digital signal processors, but I am not sure what the different suffixes signify. Maybe peruse www.ti.com to investigate.
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.
Apparent/Real power has to do with power factor, and current/voltage phase relationship. Not sure what "true power" is, unless it's another term for real power?
Bill, do you have any comments on the Power Measurement IC's. For example the Cirrus 5484 for 50/60 hz AC. That would seem to simplify the design considerably, making it more of an interface question.
@DaveWR. I'm having difficulty finding data sheets on the controllers you mention (MSP430F57197 and MSP43047197). Would you suggest some sources where I could look?
The audio was poor. I missed the first 10 minutes. I had to try various browsers before it came on. 10 minutes of music before would be nice to get everything debugged. I need to do this everyday.
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.
Or use a hybrid (analog+digital analysis) approach. Again, it depends on the question(s) you are tyring to answer re power, and what sort of details you are looking for.
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!) :)
Accuracy is something I'll touch on today--it's the old story: how much do you need? What are you trying to find out,anyway? And how much $ can you afford?
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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