3 Phase Generator Circuit - Page 1
Forum section: electronics / beginners

author: Windows9Professional
author_rank: Contributor
timestamp: February 20, 2020, 05:38:28 pm
content: 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.

author: Benta
author_rank: Super Contributor
timestamp: February 20, 2020, 07:59:03 pm
content: How powerful? Voltage? etc., etc. My crystal ball is in the workshop.

author: Zero999
author_rank: Super Contributor
timestamp: February 20, 2020, 08:10:51 pm
content: 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.

author: Windows9Professional
author_rank: Contributor
timestamp: February 20, 2020, 08:43:51 pm
content: 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

author: Zero999
author_rank: Super Contributor
timestamp: February 20, 2020, 08:45:28 pm
content: Then use a VFD with transformers connected to the output?

author: Windows9Professional
author_rank: Contributor
timestamp: February 20, 2020, 08:55:18 pm
content: 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

author: Zero999
author_rank: Super Contributor
timestamp: February 20, 2020, 09:05:08 pm
content: Quote from: Windows9Professional on February 20, 2020, 08:55:18 pmThat 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.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?

author: grifftech
author_rank: Frequent Contributor
timestamp: February 20, 2020, 09:23:23 pm
content: brushless ESChttps://www.amazon.com/s?k=brushless+esc&crid=34O7PU84BWWJ7&sprefix=brushless+%2Caps%2C167&ref=nb_sb_ss_i_5_10

author: Windows9Professional
author_rank: Contributor
timestamp: February 20, 2020, 09:58:59 pm
content: 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

author: Benta
author_rank: Super Contributor
timestamp: February 20, 2020, 10:24:20 pm
content: 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

author: David Hess
author_rank: Super Contributor
timestamp: February 21, 2020, 01:17:20 am
content: Quote from: Windows9Professional on February 20, 2020, 05:38:28 pmAnalog and digital logic 3 phase oscillators are pretty easy to make but output power stages are not.

author: Windows9Professional
author_rank: Contributor
timestamp: February 21, 2020, 11:11:56 am
content: Quote from: Benta on February 20, 2020, 10:24:20 pmLike I said: I'm looking for an Low Voltage, three phase generator with reasonable current capability or for an DIY alternative

author: Windows9Professional
author_rank: Contributor
timestamp: February 21, 2020, 11:15:11 am
content: Quote from: David Hess on February 21, 2020, 01:17:20 amI was thinking of an H-Bridge with a low pass filter on the output for every phase, would that work?

author: Dave
author_rank: Super Contributor
timestamp: February 21, 2020, 12:03:02 pm
content: Electric motors are inductive, they don't need any filtering of the excitation voltage.Quote from: Windows9Professional on February 21, 2020, 11:11:56 amLow voltage and reasonable current. Gotcha. Now we know exactly what you need.

author: Zero999
author_rank: Super Contributor
timestamp: February 21, 2020, 12:10:00 pm
content: Quote from: Windows9Professional on February 20, 2020, 09:58:59 pmI 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.Quote from: Dave on February 21, 2020, 12:03:02 pmWell mains is low voltage, so a standard variable frequency drive, would meet his requirements.https://en.wikipedia.org/wiki/Low_voltage#IEC_DefinitionAC RMS voltage (V): 50 to 1 000

author: Windows9Professional
author_rank: Contributor
timestamp: February 21, 2020, 01:22:26 pm
content: 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