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Old 11-19-09, 08:05 PM   #1
Xringer
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Default AC question. Electric expansion valve??

I was reading about the 'Electric expansion valve' here,
Electric Expansion Valve Control - Feature Articles - Extra Edition - Air Conditioning, Heating & Refrigeration NEWS
How they help maintain a "constant head pressure", when I remembered
seeing one on the diagram of my new Sanyo mini-split..

It's down on the lower right side. Looks like it might be a Motor controlled valve.?


Anyways, I noticed a connection on the block diagram called, MVO. Lower right.


Magnetic Coil?? I never understood what that MVO was.. Is it the 'Electric expansion valve' control??

The other mystery is "Reactance" upper left side. Is that a pickup coil
for a spinning magnet on a motor? For speed control feedback?

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Old 11-19-09, 09:28 PM   #2
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It looks like a 5 wire stepper motor to me. But that's just a guess. It could also be a linear solenoid with position feedback.
the function of the electronic expansion valve - Refrigeration-Engineer.com forums
LEV'S and EEV's - Refrigeration-Engineer.com forums
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Old 11-23-09, 09:18 AM   #3
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Just a wild guess but maybe the "reactance" thing is a power inductor for a boost converter just like in the Prius inverter. If it has thick wires, that's probably it.
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Old 11-23-09, 09:33 AM   #4
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Quote:
Originally Posted by NiHaoMike View Post
Just a wild guess but maybe the "reactance" thing is a power inductor for a boost converter just like in the Prius inverter. If it has thick wires, that's probably it.

Or maybe the AC-to-DC circuitry needed an inductor that was too big
and heavy to mount on a small PCB.?.

I've seen more than a few heavy transformers get ripped off of their
PCBs during shipping. One time, I unpacked about a dozen large
switchers made in Mexico. About 10 of them had a free floating
5 pound transformer, crashing around inside.
The PCBs were not made out of G10, but some cheapo beige fiberboard.
The nuts & bolts popped nice holes in the boards.
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Old 11-23-09, 05:02 PM   #5
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I don't think an A/C would need such a large inductor unless it had a boost converter or a current mode inverter.
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Old 11-29-09, 08:39 PM   #6
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I was reading your install log again out of curiosity and I noticed the relatively high power factor rating (0.9-0.95) on the specifications. So the "reactance" is very likely an active PFC boost inductor.
http://techno-fandom.org/~hobbit/cars/ginv/615dcdc.jpg
That picture of the Prius DC/DC converter should give you an idea of how high power inductors and transformers are usually connected to circuit boards. I would expect the inductor in the A/C to be similar to the one in the Prius DC/DC except it would be wound with many turns of Litz wire due to the high HF AC currents going through it. (The one in the Prius DC/DC is a smoothing inductor so it does not have much HF AC going through it and therefore is wound with solid wire. In fact, skin effect would help further reduce noise by increasing impedance at higher frequencies.)

And with the effect of the active PFC reducing peak currents, the cheap power meter you put on it should be fairly accurate.
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Old 12-08-09, 08:11 PM   #7
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Since you now posted the service manual in your other thread, I can pretty much confirm that the inductor is for an active PFC/boost converter. On page 38:
Quote:
In order to further improve inverter performance, control is switched between PWM control at low operation speeds, and PAM control at high operation speeds, making the most effective use of power.
At low speeds, the boost converter only operates as an active PFC and PWM is used to reduce the voltage to the motors. At high speeds, the boost converter increases the voltage to the inverter. Exactly like how the Prius inverter works.
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Old 12-09-09, 08:38 AM   #8
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I remember skimming over that part of the manual and having no clue what PFC was..
I speculated it might have been more like standard DC than pulses.
Anyways, I will read more about it, and the mystery of the "Reactance" coil will be over.

Thanks. It's reassuring to know my Sanyo is a Prius in the heat-pump world.

It's getting cold and snowy, cranking up our power usage to 10-12 kWh a day.
Paying $2 to $2.40 a day for stealing heat from the cold air, is a lot less
than buying 2 to 4 gallons of oil every day..
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Old 12-12-09, 08:43 PM   #9
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I was doing some research about the Prius inverter for my ECEN 370 class and I found this:
VH boost
Quote:
Interesting things happen in the 30 - 40 MPH region, especially in EV mode.
I know from some other observations that the inverter drive signals for MG2
move from a multiple-kilohertz PWM regime into simply switching 3-phase square
waves at the motor's native electrical rotation speed, because it's more
efficient and the motor is turning fast enough to smooth out any torque ripple
that would produce. But overall applied motor current can still be regulated
smoothly! How? By using a variable boost voltage. In this speed range I see
VH rising and falling corresponding to my go-pedal demand, with its lowest
baseline creeping up a bit as I head toward 40 MPH and MG2's own peak output
rises sufficiently. It's almost like having the switching behave like a
brush commutator, simply leading the electrical rotation angle by 60 or more
degrees, and regulating motor speed via applied voltage like it was a big ol'
toy-train rheostat.
I find that quite interesting, but then again, I have a big interest in power electronics. And my best friend Allie Moore said that I would be the next Nikola Tesla...

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