General > General Technical Chat
Microwave oven PWM frequency
NiHaoMike:
--- Quote from: tom66 on June 25, 2020, 07:26:18 am ---The only failure is the plastic that's glued to the front of the door has peeled off. Funnily enough the same failure has happened to the one in the work kitchen (same generation, different model.) I have yet to find an adhesive that survives the high temperature of the oven's operation so I haven't been able to glue it back on permanently yet.
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Have you tried JB Weld?
--- Quote from: Yansi on June 25, 2020, 10:15:34 am ---No, because inverter microwave just means that the bulky transformer supply was replaced by a high frequency inverter. The magnetron is still there, spewing all sorts of shit somewhere in the 2450 MHz or so. There is no control over the frequency possible. Neigher does the magnetron run on DC voltage, it still uses the pulsed rectified voltage from mains. There would be no benefit in running the inverter from DC, in fact that would be an disadvantage.
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I don't see why you couldn't "emulate a busy network" using a separate transmitter and take advantage of the collision avoidance mechanism that Wifi uses. (Make the oven appear like another network that nearby networks should avoid colliding with.) Actually, come to think of it, you don't even need an inverter microwave to do it to some extent. The inverter just gives you more flexibility in being able to turn the output on/off at will. With a conventional microwave, you could add a separate filament transformer and then gate the HV supply on and off with a SSR.
tom66:
--- Quote from: NiHaoMike on June 25, 2020, 12:44:03 pm ---
--- Quote from: tom66 on June 25, 2020, 07:26:18 am ---The only failure is the plastic that's glued to the front of the door has peeled off. Funnily enough the same failure has happened to the one in the work kitchen (same generation, different model.) I have yet to find an adhesive that survives the high temperature of the oven's operation so I haven't been able to glue it back on permanently yet.
--- End quote ---
Have you tried JB Weld?
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I've not, actually. Is there a specific one I should use?
Yansi:
--- Quote from: NiHaoMike on June 25, 2020, 12:44:03 pm ---
--- Quote from: tom66 on June 25, 2020, 07:26:18 am ---The only failure is the plastic that's glued to the front of the door has peeled off. Funnily enough the same failure has happened to the one in the work kitchen (same generation, different model.) I have yet to find an adhesive that survives the high temperature of the oven's operation so I haven't been able to glue it back on permanently yet.
--- End quote ---
Have you tried JB Weld?
--- Quote from: Yansi on June 25, 2020, 10:15:34 am ---No, because inverter microwave just means that the bulky transformer supply was replaced by a high frequency inverter. The magnetron is still there, spewing all sorts of shit somewhere in the 2450 MHz or so. There is no control over the frequency possible. Neigher does the magnetron run on DC voltage, it still uses the pulsed rectified voltage from mains. There would be no benefit in running the inverter from DC, in fact that would be an disadvantage.
--- End quote ---
I don't see why you couldn't "emulate a busy network" using a separate transmitter and take advantage of the collision avoidance mechanism that Wifi uses. (Make the oven appear like another network that nearby networks should avoid colliding with.) Actually, come to think of it, you don't even need an inverter microwave to do it to some extent. The inverter just gives you more flexibility in being able to turn the output on/off at will. With a conventional microwave, you could add a separate filament transformer and then gate the HV supply on and off with a SSR.
--- End quote ---
It already appears as a busy network channel already. It doesn't matter how did a packet got corrupted.
Why would you add a SSR? What for? To further make more EMI/RFI and increase the apparent power input?
Microwave oven designs are already very optimal. Adding unnecessary shit doesn't make it better.
chris_leyson:
--- Quote ---The primary manufacturer of inverter microwaves is Panasonic, whose microwave ovens have a great reputation, and AFAIK no issues whatsoever with longevity. (They’re all I’ve used for 20 years, and I’ve never had one die. I’ve only gotten new ones because of moving to a country with different mains voltage, or to upgrade to one with new features.)
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Modern microwave ovens fitted with inverters such as Panasonic, Bosch and Siemens will generate continuous microwave energy from 1kW down to 360W or so, below that they switch over to PWM. By clever and subtle design an inverter will control a magnetron over a 1:3 power range. If they come with a grill or convection fan they can be used with or without additional microwave heating and actually produce some very well cooked meals. I know because I help design them.
The older ovens with transformer driven magnetrons are really crude by comparison and there isn't a great deal of food stuff that you can cook in the traditional sense. My old school cheap popty ping, or is it popty beep these days, is just used for warming.
tom66:
One thing I *don't* like about our Panasonic combi microwave-inverter is the fan. It runs for about a minute to "cool down" even if you only used the oven for 10 seconds to briefly zap something, in which time almost no heat is produced. There seems to be no temperature monitoring, or estimated power dissipation, in the control logic. The fan is noisy and while it's not a massive problem, it strikes as something that could have easily been addressed in the software.
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