Author Topic: 3 Phase Generator Circuit  (Read 1507 times)

0 Members and 1 Guest are viewing this topic.

Offline Windows9ProfessionalTopic starter

  • Contributor
  • Posts: 20
  • Country: at
3 Phase Generator Circuit
« on: February 20, 2020, 05:38:28 pm »
For testing of an three phase induction motor I would need a powerful three phase generator (120° phase shifted).

Is there a simple circuit for this job?

I was thinking of an SPWM sine generator with just 3 lookup-tables for sinewaves which are simply 120° out of phase, but that seems a bit of overkill.   
 

Offline Benta

  • Super Contributor
  • ***
  • Posts: 6420
  • Country: de
Re: 3 Phase Generator Circuit
« Reply #1 on: February 20, 2020, 07:59:03 pm »
How powerful? Voltage? etc., etc. My crystal ball is in the workshop.

 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 20364
  • Country: gb
  • 0999
Re: 3 Phase Generator Circuit
« Reply #2 on: February 20, 2020, 08:10:51 pm »
I wouldn't bother designing one, unless it was for purely educational purposes. What you're after is known as a variable frequency drive and is an off the shelf module.
 

Offline Windows9ProfessionalTopic starter

  • Contributor
  • Posts: 20
  • Country: at
Re: 3 Phase Generator Circuit
« Reply #3 on: February 20, 2020, 08:43:51 pm »
Since I only want to experiment with (self made) induction motors I better keep the voltage down for now and after some research it seems to me that Variable Frequency Drives are mainly available for mains voltages, for which I could also use the three phase mains here in Europe, but ist far too dangerous.

I'm looking for an Low Voltage, three phase generator with reasonable current capability or for an DIY alternative
 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 20364
  • Country: gb
  • 0999
Re: 3 Phase Generator Circuit
« Reply #4 on: February 20, 2020, 08:45:28 pm »
Then use a VFD with transformers connected to the output?
 

Offline Windows9ProfessionalTopic starter

  • Contributor
  • Posts: 20
  • Country: at
Re: 3 Phase Generator Circuit
« Reply #5 on: February 20, 2020, 08:55:18 pm »
That brings me to the next point:

(After my research on them) they are all around 100€ or more and even if I use a transformer to step the voltage down there will still be mains voltage involved (and a transformer also limits the current to a small extend)

and I need three transformers
« Last Edit: February 20, 2020, 09:00:48 pm by Windows9Professional »
 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 20364
  • Country: gb
  • 0999
Re: 3 Phase Generator Circuit
« Reply #6 on: February 20, 2020, 09:05:08 pm »
That brings me to the next point:

(After my research on them) they are all around 100€ or more and even if I use a transformer to step the voltage down there will still be mains voltage involved (and a transformer also limits the current to a small extend)
That doesn't seem like a lot of money to me. How was I supposed to know? You made no mention of the power output or budget. My psychic powers are failing me.  :palm:

You're wrong about the current. If a transformer steps down the voltage, it will boost the current. If you don't want to use mains, then how else are you going to power this thing?
 

Offline grifftech

  • Frequent Contributor
  • **
  • Posts: 369
  • Country: us
    • youtube channel
 

Offline Windows9ProfessionalTopic starter

  • Contributor
  • Posts: 20
  • Country: at
Re: 3 Phase Generator Circuit
« Reply #8 on: February 20, 2020, 09:58:59 pm »
Yeah I didn't provide much information at first and since I'm only a hobbyist I think I will go with the SPWM method, which fits my budget better.

I don't think that ESCs for brushless DC motors will work since these are usually meant to operate with synchronous motors instead of asynchronous induction motors
 

Offline Benta

  • Super Contributor
  • ***
  • Posts: 6420
  • Country: de
Re: 3 Phase Generator Circuit
« Reply #9 on: February 20, 2020, 10:24:20 pm »
You still didn't reply to the questions in reply #1 (from me).
If this is the quality from a "Windows9Professional" (whatever that is), then I can only say  :palm: :palm: :palm:

 

Offline David Hess

  • Super Contributor
  • ***
  • Posts: 17429
  • Country: us
  • DavidH
Re: 3 Phase Generator Circuit
« Reply #10 on: February 21, 2020, 01:17:20 am »
For testing of an three phase induction motor I would need a powerful three phase generator (120° phase shifted).

Is there a simple circuit for this job?

I was thinking of an SPWM sine generator with just 3 lookup-tables for sinewaves which are simply 120° out of phase, but that seems a bit of overkill.

Analog and digital logic 3 phase oscillators are pretty easy to make but output power stages are not.
 

Offline Windows9ProfessionalTopic starter

  • Contributor
  • Posts: 20
  • Country: at
Re: 3 Phase Generator Circuit
« Reply #11 on: February 21, 2020, 11:11:56 am »
You still didn't reply to the questions in reply #1 (from me).

Like I said: I'm looking for an Low Voltage, three phase generator with reasonable current capability or for an DIY alternative
 

Offline Windows9ProfessionalTopic starter

  • Contributor
  • Posts: 20
  • Country: at
Re: 3 Phase Generator Circuit
« Reply #12 on: February 21, 2020, 11:15:11 am »
Analog and digital logic 3 phase oscillators are pretty easy to make but output power stages are not.

I was thinking of an H-Bridge with a low pass filter on the output for every phase, would that work?
 

Offline Dave

  • Super Contributor
  • ***
  • Posts: 1356
  • Country: si
  • I like to measure things.
Re: 3 Phase Generator Circuit
« Reply #13 on: February 21, 2020, 12:03:02 pm »
Electric motors are inductive, they don't need any filtering of the excitation voltage.

Like I said: I'm looking for an Low Voltage, three phase generator with reasonable current capability or for an DIY alternative
Low voltage and reasonable current. Gotcha. Now we know exactly what you need. :palm:
<fellbuendel> it's arduino, you're not supposed to know anything about what you're doing
<fellbuendel> if you knew, you wouldn't be using it
 

Online Zero999

  • Super Contributor
  • ***
  • Posts: 20364
  • Country: gb
  • 0999
Re: 3 Phase Generator Circuit
« Reply #14 on: February 21, 2020, 12:10:00 pm »
Yeah I didn't provide much information at first and since I'm only a hobbyist I think I will go with the SPWM method, which fits my budget better.

I don't think that ESCs for brushless DC motors will work since these are usually meant to operate with synchronous motors instead of asynchronous induction motors
I don't see why a brushless motor driver won't work. The simpler and dumber the drive, the greater chance it stands of working. Try a cheap one, they're not expensive.

Like I said: I'm looking for an Low Voltage, three phase generator with reasonable current capability or for an DIY alternative
Low voltage and reasonable current. Gotcha. Now we know exactly what you need. :palm:
Well mains is low voltage, so a standard variable frequency drive, would meet his requirements.  :-DD
https://en.wikipedia.org/wiki/Low_voltage#IEC_Definition
AC RMS voltage (V): 50 to 1 000
 

Offline Windows9ProfessionalTopic starter

  • Contributor
  • Posts: 20
  • Country: at
Re: 3 Phase Generator Circuit
« Reply #15 on: February 21, 2020, 01:22:26 pm »
I'm going to try a cheap brushless motor driver and mabye realise the H-Bridge-extra low voltage inverter.

Thank you all for your time
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf