high power two step inverter design

[mtwieg]

ok, so i decided for 2KVA inverter, with power mosfets switching at 50KHZ, is it any practicable now ?????? 48v bank input ??????

Depends on the MOSFETs. The right FETs can handle 4KVA. As bradtherad states, drawing 4KW from 48V without large power losses requires heavy wiring, but it's certainly possible.

what modification i need to do with DC VFD ac motor drives????

No way to tell without looking at the specific VFD. Most VFDs will have their own rectifier circuitry for creating the DC bus voltage, so you'll have to disconnect that. But one thing to worry about is the controller for the VFD. It might now make it easy to integrate your own DC-DC converter with it, especially if it uses one controller for both its rectification stage and inverter stage. In the worst case you may have to make your own controller for the inverter, but that shouldn't be too bad.

 

[muddasirwaheedmalik]

Depends on the MOSFETs. The right FETs can handle 4KVA. As bradtherad states, drawing 4KW from 48V without large power losses requires heavy wiring, but it's certainly possible.
No way to tell without looking at the specific VFD. Most VFDs will have their own rectifier circuitry for creating the DC bus voltage, so you'll have to disconnect that. But one thing to worry about is the controller for the VFD. It might now make it easy to integrate your own DC-DC converter with it, especially if it uses one controller for both its rectification stage and inverter stage. In the worst case you may have to make your own controller for the inverter, but that shouldn't be too bad.

Thanks mtwieg, can u explain how can integrate my own DC-DC converter with it ??? i mean rectification stage and inverter stage ???

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Depends on the MOSFETs. The right FETs can handle 4KVA. As bradtherad states, drawing 4KW from 48V without large power losses requires heavy wiring, but it's certainly possible.
No way to tell without looking at the specific VFD. Most VFDs will have their own rectifier circuitry for creating the DC bus voltage, so you'll have to disconnect that. But one thing to worry about is the controller for the VFD. It might now make it easy to integrate your own DC-DC converter with it, especially if it uses one controller for both its rectification stage and inverter stage. In the worst case you may have to make your own controller for the inverter, but that shouldn't be too bad.

Thanks mtwieg, can u explain how can integrate my own DC-DC converter with it ??? i mean rectification stage and inverter stage ???

 

[FvM]

Most VFDs will have their own rectifier circuitry for creating the DC bus voltage, so you'll have to disconnect that.

Many VFD inverters are exposing terminals for the bus voltage. In addition, there's usually no problem to supply a single phase input inverter with a DC voltage instead.

 

[muddasirwaheedmalik]

Well then it woiuld solve a lot of problem, all i have to get an industrial single phase 3-4KVA drive controller with probably exposed bus voltage, set its frequency to 60Hz , output 220V and put on my 48Vdc to 380vDC converter. .Seems nice
Just two questions, size of capacitor for voltage regulation, should i add any to my dc-dc inverter or simply send my rectified 50KHZ signal to it ?
How to ensure voltage regulation , should dc feedback to oscillator should be from dc converter output or the VFD output (global then)
what would u recommend as switching frequency, i am gonna use ferrite EI core with suitable MOSFET.

regards.

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Well then it woiuld solve a lot of problem, all i have to get an industrial single phase 3-4KVA drive controller with probably exposed bus voltage, set its frequency to 60Hz , output 220V and put on my 48Vdc to 380vDC converter. .Seems nice
Just two questions, size of capacitor for voltage regulation, should i add any to my dc-dc inverter or simply send my rectified 50KHZ signal to it ?
How to ensure voltage regulation , should dc feedback to oscillator should be from dc converter output or the VFD output (global then)
what would u recommend as switching frequency, i am gonna use ferrite EI core with suitable MOSFET.

regards.

 

[muddasirwaheedmalik]

one more question , i suppose there would be no neutral /live output in the VFD ???

 

[D.A.(Tony)Stewart]

The ID500A-030 Darlington looks good for driving an electric forklift but I think brokers will drool if you ask them for a price. Don't fool yourself, these will not be cheap. It doubt your 4kVA "budget inverters" are rated for motors. You may have to re-consider your spec and disclose your budget for this design. I suspect a transformerless solution is needed.

Similar to the Tesla Car with >800 parallel MOSFET's. THe advantage of MOSFET's is the possibility for PTC on V vs I for easy parallel mode or ganging of switches. IGBT's are are great for high voltage and high current but have a severe NTC and must come from same batch in order to run in parallel easily..

I think Goldsmith was right, if it is a cheap inverter you want, you need to figure how to incorporate inexpensive switches with low cost magnetics. So what is your budget?

It could range from 10 cents ~$x / kW? but depends on what qty? burdened volume cost or prototype cost?

 

[muddasirwaheedmalik]

Sunnyskyguy thanks for good reply. However i must clarify that i already have these ID500A-030 i have a source which goldmine these power mosfets, diodes, BJTS, IGBTs silicone ultra fast fuses , all high wattage and values, i know that ID500A-030 is not cheap but i have some pairs of these, i also have EUPEC FZ 1800 R 12 KL4C which is 11.2KW IGBT's i am enclosing data set for it as well if you think ID500A-030 is not good for this job i can use it , if you think that its not cheap in market. BTW if trading is allowed on this forum i can get u these or other modules for fair price through e-bay/amazon/pay-pal for secure , used but working guranteed on arrival. regards,

BTW can u please clarify what is meant by "budget inverters" are not rated for motors, ???? what do u mean by that, i really want a transformerless design usign VFD .regards

 

[D.A.(Tony)Stewart]

I suppose you have existing AC motors too. What A-hr rating does the 48V system have?
I'm not sure why you are trying to convert battery to AC is this for a fixed motor or mobile? car? boat? bike?
DC motors might be more efficient and less expensive .

Rated Voltage: 24V/36V/48V/72VDC
Rated Power: 3KW/3.5KW/4KW/4.5KW/5KW
Variable Speed: 1450rpm/1500rpm/1800rpm/2000rpm/2500rpm/2800rpm

I'm sure you can use the 500A Darlington's to run a 20A motor and easily run a 100A DC motor.
What is missing I think is some kind of system level design for Power distribution, efficiency and power budget for losses.
THere is a cost to conversion, distribution then motor control then motor efficiency.
How much power can you afford to lose?
Or are you just trying to run existing AC motors as a UPS safety backup system? using parts you have for an existing general requirement.

 

[muddasirwaheedmalik]

Oh . i think perhaps u might have overlooked the design objective. long brown outs here. the objective is to make a UPS for home use, the transformerless design assumption is high efficiency coupled with cost of huge 4KVA 48vdc to 220v stepped sine inverted, thats why i proposed a high frequency Dc to DC converter using a much smaller ferrite transformer and then use 380v dc rails to feed H brdigge of VFD and get 60Hz , 220V stepped sine output for home appliance usage. i hope i clears the mission statement.
regards

 

[D.A.(Tony)Stewart]

Correct I did not read any objective. Still an overall spec is needed. Is this for resistive loads? capacitive? inductive ? heavy surge loads like incandescent lamps or fridge motor.
The reason I ask is this affects overall design and choice of batteries and length of time you wish to maintain power.
Next is quality of power with harmonic content? How much is OK? 5%? 30%? Square wave ok?
So please identify time, starting load and nominal load or steady state load during normal power so no starting surge on power fail only sustain certain loads because 4kVA is not much. Is it just for computer and modem?

So this is just a cheaper solution required for your personal use?
Is this somewhat like what you need? https://www.apc.com/products/resource/include/techspec_index.cfm?base_sku=PS2200I

Mission may be possible but still needs a budget for materials and time with scope of performance.

 

[muddasirwaheedmalik]

probably one refirdgratror, 4 Tvs lcs, 6 fansm 20 envergy saver lights, one hour brown out regularor feature, with 48V i can make 4KW one hour if get recharge time 3-4 hours. now please help me with plan. i want to get rid of my extremely inefficient 60Hz step up 4KVA tranformer on modified sine wave with higly inefficiency and extreme heat loss ??????
SMPS charger replacing Transformer based linerar charger i have a 3KVa charger 48V, i have IGBT/mosfet modules and SG based kits for 30KHZ switching , hence needing a small ferrite core, i assume i can place it in a small PSU case with fan cooling, after rectification 380V dc i then feed it to to the H-drive for UPS home use. Siggestions please

 

[FvM]

i want to get rid of my extremely inefficient 60Hz step up 4KVA tranformer on modified sine wave with higly inefficiency and extreme heat loss

Saving weight and size would sound like a more reasonable motivation. But efficiency of suitably designed 60 Hz transformers is generally high. Although the losses of a high frequency transformer may be lower (assuming "high tech" litz wire or flat wire/foil windings), the overall losses converter are often higher due to increased switching losses.

 

[ALERTLINKS]

60Hz , 220V stepped sine output for home appliance usage. i hope i clears the mission statement.
regards

By the way,
as you are in Pakistan, here mains frequency is 50Hz, not 60Hz.

 

[D.A.(Tony)Stewart]

In order to be successful in designing a system , you need to do more research on the requirements, preferably with a power monitor. Otherwise you will have many surprises like localized brownouts or system failure when fridge starts and you need to decide if inverter will be auto transfer and at what threshold, continuous on , manual transfer.

Keep in mind Run Stop Run won't work on most fridges as they take a while before they can be restarted.

Item Surge power Duration. Steady RMS power
1.
2.
3.
4.

Once you understand the range of average to peak and overload conditions, alarm threshold, etc, you might have an idea how to design one. Until then, keep learning before doing... or get propane fridge or generator.

What battery capacity do you need for CCA to start everything? Keep in mind ESR of each battery in series is additive.
What is the A-HR capacity of battery do you need?

Do you have a budget?

This is how I learnt as an engineer to design things... with specs 1st, before even thinking of components, unless cost of failure was not an issue. It is like building a house without a plan. Can be done, only if you have done it before.

 

[BradtheRad]

A refrigerator motor (AC motor) runs more efficiently on sine waves. If you feed it square waves, it will draw maybe 10 percent more current continually.

Additionally the motor draws a surge current when it starts up. This can be 2 to 3 times normal running current.

If other appliances are drawing too much current at the same time, the refrigerator motor may not be able to start.

These factors make the refrigerator a prime concern in a backup power system, especially if you need it to keep vital medications cool.

 

[ALERTLINKS]

**broken link removed**
Here is a 15KWatts inverter project. It uses JAL for microcontroller programming as you do.
**broken link removed**
This is source code for 16F628, which can be modified. It is to drive hiddge delivering sinewave output at 60 Hz. There are 328 steps for full wave.
You can take many ideas about HF transformer winding on this page.

**broken link removed**

Project files and pictures,
**broken link removed**

 

[picgak]

Hi ALERTLINKS,
I already tried to compile the JAL file above it gave errors and most of the part is in asm where i am weak. But the compiled hex file is also available there, but you will not get the fun while building your own code if you use others file. so i left it. Do you use JAL if you do please tell.
regards ani

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