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Has anyone tried VFD inverter with fixed frequency
#1
Just realised - how do I move this post to the General Project thread ???

I have used a couple of Variable Frequency Drives with some 3 phase motors in the past and wondered why (appart from the high input voltage) they are never used as general purpose inverters if they are set with a fixed frequency output.

The inverters normally take 110V or 220V as input, pass through a bridge rectifier to DC and then re-output as an AC waveform.

I'm looking at an option of creating a large output inverter from cheap parts....

This is the outline....

Separate note : how can I set the image size in the post larger than default ?

I know the VFD units have feedback / detection for motors but if the output frequency is hard set should the unit at least output a steady AC waveform ?

Separately I have an existing machine with a 2.2kW motor that already has an inverter drive and plan on feeding this with the output from 2 UPS units as DC so that I can run it from my battery without having to get a separate >3kW inverter.
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#2
(05-02-2018, 05:42 PM)completelycharged Wrote: Just realised - how do I move this post to the General Project thread ???

Moved

(05-02-2018, 05:42 PM)completelycharged Wrote: Separate note : how can I set the image size in the post larger than default ?

You can't attach an image and set it's size. The visitor must click the image to see a large image. If you want to set the size, then you need to save the image to an online storage, grab the link, and the use the Full Editor to insert the image. Then you can set the size from there. You only need to specify 1 of the dimensions, the scripts will handle the other one (like, if you import an image and want it to be 400px but don't know the other number, just leave it blank and it'll automatically be set)
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#3
(05-02-2018, 05:42 PM)completelycharged Wrote: Just realised - how do I move this post to the General Project thread ???

I have used a couple of Variable Frequency Drives with some 3 phase motors in the past and wondered why (appart from the high input voltage) they are never used as general purpose inverters if they are set with a fixed frequency output.

The inverters normally take 110V or 220V as input, pass through a bridge rectifier to DC and then re-output as an AC waveform.

I'm looking at an option of creating a large output inverter from cheap parts....

This is the outline....

Separate note : how can I set the image size in the post larger than default ?

I know the VFD units have feedback / detection for motors but if the output frequency is hard set should the unit at least output a steady AC waveform ?

Separately I have an existing machine with a 2.2kW motor that already has an inverter drive and plan on feeding this with the output from 2 UPS units as DC so that I can run it from my battery without having to get a separate >3kW inverter.
The output is usually rated power
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#4
What's your load? All VFDs I've seen so far require high inductance (motor) as load and have square wave output or best case three level inverter so modified square wave.
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Indexed: 53
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Broken down, untested: ~800
Not yet broken down: ~140 kg
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#5
While I had been using some VFD I had thought that the output could be smoothed (worst case with a small motor that is unloaded). The VFD usually PWM the output at 8kHz upwards, which is the high pitch noise you can hear with them. Inverters only use the smae method of PWM to re-create a sinewave.

I am still thinking about the potential to use them, for solar installs there may be a way to use them to avoid having to go down the zero export limiter route.....
If you can't quantify how much they cost, it's a deal, I'll buy 5 of them for 3 lumps of rocking horse ......
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#6
The inverter is equivalent to an inverter in that it removes the input rectifier. A part of the inverter has two terminals of the dc bus leading out. If the appropriate dc current is input from these terminals, it is equivalent to an inverter. Different from the general inverter, its output frequency can be changed or fixed. Hope I can help you
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