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220v 50hz to 110v 60hz project need feedback

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Leo M.

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Hi all,

I've been doing research on trying to build my own frequency converter using off the shelf parts. I'm currently considering doing the conversion as an AC-DC-AC. Here's how I proposed to do it, and I hope to receive feedback.

Background: I'm currently living in China, and I have some motors that need to run 24/7 (Austin Air HM400). Purchasing the Austin air is possible in China, but it would be 2.5x the price it is in the United States, and I cannot live in China without an air filter as many of us are being killed by the pollution. I'm hoping to find a way to do this cheaply and easily and then share the project with others who might also benefit.

Here is the link to the Austin Air HM400 owner's manual: https://www.sylvane.com/media/documents/products/Austin-Air-Healthmate-Owners-Manual.pdf

For my AC to DC conversion, I'm purchasing a Chinese ATX power supply (used in computers). The maximum wattage from my Austin Air HM400 is 170w, so I've chosen a 400 watt ATX power supply to start with. Essentially, what I'll do is cut off all the yellow line and black lines from the power supply and splice them together to create 12V and ground wires. The green load wire will be connected to ground to ensure the ATX power supply remains on all the time. There is a load requirement for these power supplies, but I don't know how to deal with it, so I won't plug it in unless it's plugged into one of my units. The advantage of this method is that it will already be wired for home use and the proper plug in Chinese homes.

The process for converting one of these ATX for use as a bench supply is shown in these guides: https://www.instructables.com/id/Encyclopedia-of-ATX-to-Bench-Power-Supply-Conversi/

The wires from the ATX power supply I will connect to a DC-AC inverter. This will be a basic inverter with a pure sine wave output (modified sine wave may cause heating issues with the electric motor, so I'll opt for the higher priced pure sine wave).

Something like this: https://www.amazon.com/Wagan-EL2601...pebp=1434808159726&perid=0DQS5J7Z1P9EE213PRFR

I will crimp on the connectors to my 12V and ground lines and screw them onto this inverter. The inverter already has the proper plugs for the 110V 60Hz that I need, so the entire assembly will be placed into a project box enclosure.

****Here's where I need feedback****

First of all, any feedback on whether or not you believe this approach will work. The total cost for this is around $150 and is much cheaper than the options on the internet for a frequency converter, but I lack the experience to foresee issues with the design. Please let me know if there's something else I should do before hooking all this stuff up.
 
Have you looked at the possibility of changing the motor to a 220V, 50Hz unit?
 
Yes, I contacted Austin Air about it, and was told to contact a 3rd party company who would handle the motor change-outs, but the cost exceeded the price of the unit itself, which meant it was cheaper to purchase a new unit in China considering the additional cost of a frequency converter.

As for changing the motor myself to a third part, I would void the 5 year warranty on the Austin Air unit. The ideal solution would be to deal with the frequency conversion firstly.
 
Yes, I contacted Austin Air about it, and was told to contact a 3rd party company who would handle the motor change-outs, but the cost exceeded the price of the unit itself, which meant it was cheaper to purchase a new unit in China considering the additional cost of a frequency converter.

As for changing the motor myself to a third part, I would void the 5 year warranty on the Austin Air unit. The ideal solution would be to deal with the frequency conversion firstly.
That looks like a simple machine and the main thing that could fail is the motor itself, which are typically very reliable.
If you got a new 220V/50Hz motor then you wouldn't need any frequency converter.
 
Check the ATX spec. Most of the power available is probably at 5V. How many of those 400W Watts are available at 12V ?
But I agree with Crutschow; replacing the motor seems the better option. You might even get a 5yr warranty with the new Chinese motor :D.
 
12V in a computer is used to drive low power CD motors and fans. It will not provide 170W (14.2A).
 
What would happen if you just ran the motor on 50Hz? Can you live with it if motor just runs 5/6 of the speed?
 
Seems simple to me? The motor is ~115w permanent split phase 3 speed motor 1.3amps,
A small low Va 250v to 120v transformer should be all that is needed?
The motor is 3 speed anyway.
Max.
 
Looking at the Warranty, I wouldn't worry about Voiding it.
It is Pro-Rated and subject to additional shipping costs.

And Considering that even Cigarette Smoke Voids the Warranty.
Where you live, it may be Void for what is in Your Air.

I Also Agree, Just use a Transformer for 120 VAC and at the 50 Hz.
The Lower Air flow won't make much difference.
 
As others said just use a common step down transformer.

Now as the ATX power supplies go they are terrible for most anything but computer power sources.

Exspecially for loads that require high 12 volt current without putting any load on the 3.3 and 5 volt rails unless you do some moderate circuitry rework to repurpose them to being 12 volt only power sources and that's not something just anyone with basic electronics skills can do.
 
I had looked at whether it would be fine to just step down the voltage and not worry about the frequency, but on a few other forums they had comments worrying about the generation of heat, such as this:

"Operating at 50hz will slow the rotor.The speed of an induction motor is given by 120*frequency/no pole of motor less 4% for full load speed.

The BIG problem comes when you transform the voltage to 110v ac 50 hz. This violates the rated airgap flux of the motor and results in magnetic saturation giving rise to Excessive heating!!!!"

Since these units will be running 24/7, will this become a fire hazard if they run a bit hotter, or is this really not a concern?
 
audioguru: If you connect up all the yellow lines together into one bundle, you can achieve much higher available amps. If you look at my link above or the ATX bench conversions they show how they achieve the higher amperage/wattage. Again, I'm no expert so please let me know if I misunderstood this.
 
What you need is a transformer that drops the voltage to about 50/60 * 120V = 100V @ 50Hz.
That would keep the motor magnetics from saturating and avoid excessive heating.
 
If getting 120 VAC 60 HZ is that big of concern there are a number of cheats that can be done if you have any reasonable electronics skills.

One is to step your voltage down to 110- 120 VAC 50 Hz then rectify it to DC and send that higher voltage DC directly into the HV DC side of a 120 volt 60 Hz sine wave inverter and use a small universal 12 VDC output power pack to power the inverters lower voltage electronics, but with the power circuits to the high current switching devices disconnected, so it thinks it's running off a 12 volt source but its not actually having to run the step up part of its internal systems.
 
crutschow: I just found another site that is saying the same thing you did. This might be the solution I'm looking for as it's incredibly easy to find a 100v solution. Here's what I found on another site:

"If the voltage applied to the motor is held constant and the frequency is reduced, the current will increase and in theory, the torque will also increase. The motor should be able to deliver the same power also, BUT the flux in the iron is now too high resulting in excessive iron loss, and the motor will fail prematurely. Above a very low frequency, (5 - 10Hz) the impedance of the magentising circuit of the motor is primarily inductive and so in order to keep the flux within limits, it is important to keep a linear V/F ratio (Voltage to Frequency ratio). If the frequency is reduced by 10%, the voltage must also be reduced by 10%. Because the flux in the iron remains the same, the torque capacity remains the same and so the power rating of the motor also drops by 10%."

"60Hz rated motor on 50Hz
Provided the voltage is dropped by the same proportion as the frequency, it is OK to run a 60Hz motor on 50Hz. The speed will be reduced by the reduction in frequency and the power capacity will also reduce by the ratio of the reduction in frequency."

The Frequency change from 60Hz to 50Hz is 16.7%. The equivalent change to the voltage is 120V to 99.6V. Seems this would be a safe and easy solution to try @ 100V/50Hz.

Thanks for the extremely helpful suggestions everyone. If anyone is an electric motor expert and doesn't agree with this latest idea, please let me know.

My best to all of you in the forum.
 
audioguru: If you connect up all the yellow lines together into one bundle, you can achieve much higher available amps. If you look at my link above or the ATX bench conversions they show how they achieve the higher amperage/wattage. Again, I'm no expert so please let me know if I misunderstood this.

No. You will only have a higher current carrying Capacity. All the similar coloured wires originate from the same "point" in the supply unit.
 
Ramussons: Some of the project folks who were doing the bench supplies said that to get all the amperage you needed to connect all the lines to connect all the available rails. Here's their feedback:

"Group the 4 wire colors together and cut them to length to where you marked where the posts would go. Use the wire strippers to take off the insulation and stick about 3-4 wires into one tongue terminal. Then crimp them. The exact number of wires per voltage rail depends on the wattage of the PSU. Mine was a 400W and there are about 9 wires per rail. You need all these wires so that you can get all of the current rated for that rail."

It was from this project: https://www.instructables.com/id/Convert-an-ATX-Power-Supply-Into-a-Regular-DC-Powe/?ALLSTEPS

If this is wrong, sorry I was going by the information presented by the project folks.
 
The two potential problems with an ATX power supply are that:-
1) It is designed to run with most of the output power on the 5 V line, so it may not regulate the voltage properly unless a minimum load is provided to the 5 V line.
2) It is designed to run with most of the output power on the 5 V line, so the 12 V line may not be able to provide anywhere near the rated power.

The Instructables article has a load resistor to give a minimum load. On that particular power supply, the load resistor on the 12 V worked. The output was quoted as 23 A which is 276 W, which is well under the 400 W of the power supply rating.

If you do use an ATX power supply, find out what the current rating for the 12 V supply is, and stay well under that.

(The Instructables article suggested a 10 Ω, 10 W resistor on the 12 V supply. As that would be dissipating 14.4 W, it is either running far too hot or something is different on the power supply.)
 
Ramussons: Some of ............

If this is wrong, sorry I was going by the information presented by the project folks.

No, it's not wrong it that sense. The project folks just bunched up all the same voltage feeds to reduce the voltage drop from the supply unit. One may as well remove all the Yellow (12 volts) wires and use a single thicker wire instead.

the ATX PSU has ONE 5 Volt point ( ignoring the small capacity 5 Volt standby feed) and ONE 12 Volt point inside the unit. It has independent wires for each outlet connector.
 
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