Another homebrew AC-controller - Page 149 - DIY Electric Car Forums

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#1481
01-07-2017, 03:48 PM
 PStechPaul Senior Member Join Date: May 2012 Location: Cockeysville, MD 21030 Posts: 2,939
Re: Another homebrew AC-controller

I just read the parameters of one winding of a 1.5 HP 4 pole 3 phase motor:

R(100Hz) = 6.27 ohms
R(1kHz) = 27.9 ohms
R(10kHz) = 442 ohms

L(100Hz) = 30.7 mH
L(1kHz) = 27.4 mH
L(10kHz) = 18.5 mH

I'm not sure how that scales to an EV motor of, say, 30 HP, or to the current for use as a boost inductor, but let's say the EV charger was 30 amps while the 1.5 HP motor would be used at 1.5 amps (1 amp per HP). Also let's say the input is 72 VDC to be boosted 5x to 360 VDC. To get 360 VDC at 1.5 amps would require 7.5 amps from the 72 volt source. With 30 mH inductance and 72 volts it would take 7.5 * 30 / 72 = 3 mSec to get 7.5 amps peak, and a comparable time to transfer the energy to the output. So perhaps 10 mSec period or 100 Hz might work for such a boost converter. These are just off-the-wall calculations, but I doubt that the boost converter could run at any higher than 1 kHz.

Please check my calculations and assumptions, and perhaps take similar AC resistance and inductance readings on the motor you are using. I might run a simulation, or even try making a boost converter with the motor I have. The reading is just for one winding, so with two in parallel the inductance should be the same but resistance would be half, and with all three phases connected the values are difficult to determine, especially since the windings have a common core and interaction with the rotor.

#1482
01-07-2017, 05:00 PM
 jhuebner Senior Member Join Date: Apr 2010 Location: Germany Posts: 678
Re: Another homebrew AC-controller

Well, practically I tried 17.8kHz with my forklift motor and 8.8kHz with my 18.5kW Lenze Motor. That worked as described earlier, 92%/96% efficiency.

I tried earlier with a 1.5kW 230V motor like you described, that didn't work brilliantly indeed. But thats not a practical EV motor anyway.
#1483
01-10-2017, 02:07 PM
 arber333 Senior Member Join Date: Dec 2010 Location: Slovenia Posts: 500
Re: Another homebrew AC-controller

Quote:
 Originally Posted by jhuebner Right, thats the idea. Of course in your example if you have 400V input your pack needs to be >564V discharged for it to work. Just realized I need to handle the case when the inverter is still switched on and the user plugs in mains. A simple relay as in my first drawing would dump rectified mains on the closed bottom switch of the respective phase.
Well good luck with finding such nominal DC voltage (besides Johannes) at boost... I will probably try boost from single phase and if that works buck from 3phase. That should be interesting.

I have a solution for inverter still being active when AC comes online.
I used a simple 230Vac relay to trigger the Emgcy pin when AC is on. So as not to drive off when charging.

Johannes does your charger mode start only when the key is ON or anyway? Inverter should just get 12V somehow yes? Start pin is not needed for this.

A

#1484
01-10-2017, 02:47 PM
 jhuebner Senior Member Join Date: Apr 2010 Location: Germany Posts: 678
Re: Another homebrew AC-controller

Quote:
 Originally Posted by arber333 Well good luck with finding such nominal DC voltage (besides Johannes) at boost... I will probably try boost from single phase and if that works buck from 3phase. That should be interesting.
A local company has built a couple of Mercedes Sprinter Vans on 800V. But you're right, it's still a pretty exotic setup. At least until car makers realize it's easier to fast charge a HV battery than a LV battery.

Quote:
 Originally Posted by arber333 I have a solution for inverter still being active when AC comes online. I used a simple 230Vac relay to trigger the Emgcy pin when AC is on. So as not to drive off when charging.
Yeah but that way the charger won't start as you have disabled one of the inhibit pins. You would need just a short low pulse on the emgcy pin. Like connect it to both NO and NC contact and use the dead time. That way drive mode would be safely disabled. When charge mode is active you can't drive anyway.
Question remains: emgcy stop pin is 16Hz low pass filtered, so there is a small delay between AC coming on and PWM disable. I'm actually considering some kind delay-relay so AC into the rectifier arrives after (like 100ms) the disable pulse.

EDIT: this just got me thinking: I should check the startup time of my AC/DC converter for the aux battery, maybe that is around 100ms.

Quote:
 Originally Posted by arber333 Johannes does your charger mode start only when the key is ON or anyway? Inverter should just get 12V somehow yes? Start pin is not needed for this.
start pin is indeed not needed. Just 12V power to the inverter (and inhibit pins)

Last edited by jhuebner; 01-10-2017 at 02:56 PM.
#1485
01-11-2017, 02:10 AM
 jackbauer Senior Member Join Date: Jan 2008 Location: Ireland Posts: 1,579
Re: Another homebrew AC-controller

Well yes my plan would be to boost single and buck three phase. Does the current software support buck mode also?
__________________
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#1486
01-11-2017, 02:15 AM
 jhuebner Senior Member Join Date: Apr 2010 Location: Germany Posts: 678
Re: Another homebrew AC-controller

Yep, buck is supported.

I'm working on my web site to have the information easily available.
#1487
01-11-2017, 12:39 PM
 jhuebner Senior Member Join Date: Apr 2010 Location: Germany Posts: 678
Re: Another homebrew AC-controller

Website updated: http://johanneshuebner.com/quickcms/...arging,27.html
#1488
01-11-2017, 01:08 PM
 onegreenev Senior Member Join Date: May 2012 Location: Marysville, CA Posts: 3,624
Re: Another homebrew AC-controller

Quote:
 Originally Posted by jhuebner Yep, buck is supported. I'm working on my web site to have the information easily available.
Hoping to get back to my project here real soon. Nice to follow the charging abilities. Buck being the most desired for high current low voltage packs.
__________________
Change comes, one conversion at a time.
http://onegreenev.blogspot.com/

#1489
01-11-2017, 01:18 PM
 Tomdb Senior Member Join Date: Jan 2013 Location: Warwickshire, UK Posts: 526
Re: Another homebrew AC-controller

Johannes, very clear update. I need to get a car built so I can actually start using my gathered EV components

I wonder how much power you could pull with one of these from a three phase charging station (EU one so 230v x 3). Should be 32 amps x 230 x 3.
#1490
01-15-2017, 02:39 PM
 dima Member Join Date: Dec 2015 Location: British Columbia, Canada Posts: 48
Re: Another homebrew AC-controller

Johannes your website says Boost(4) Buck (5) but the firmware description says:

"chargemode 0=Off, 3=Boost, 4=Buck"

not to confuse with opmode that is also needs to be set same?

0=Off, 1=Run, 2=ManualRun, 3=Boost, 4=Buck, 5=Sine, 6=AcHeat

mistake somewhere on your website or firmware?

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