lorenfb
Posts: 2598
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Regen circuit questions

Using figure 5 of the Texas Instruments datasheet, which represents the typical motor controller of an EV,

https://www.ti.com/lit/an/slua963a/slua ... 0513375551

one will notice the parallel diode within each of the six IGBTs, which gets forward biased when an EV enters its
re-gen mode (motor voltage greater than the battery voltage). Each winding of the motor will then conduct
a charging current back into the battery thru the upper and the lower IGBT diodes. The controller (MCU)
determines which mode the IGBT operates in by controlling its gate signal.
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 28K miles, SOH 105Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F
coulomb
Posts: 188
Joined: Thu Oct 09, 2014 5:08 pm
Delivery Date: 07 Mar 2015
Leaf Number: 200445
Location: Brisbane, Australia

Re: Regen circuit questions

edoc wrote: Thu Apr 21, 2022 11:43 am So you think thats the actual Leaf Schematic ??
Yes.
2012 Leaf with new battery May 2019. New to me June 2019.
coulomb
Posts: 188
Joined: Thu Oct 09, 2014 5:08 pm
Delivery Date: 07 Mar 2015
Leaf Number: 200445
Location: Brisbane, Australia

Re: Regen circuit questions

lorenfb wrote: Thu Apr 21, 2022 3:13 pm ... one will notice the parallel diode within each of the six IGBTs, which gets forward biased when an EV enters its
re-gen mode (motor voltage greater than the battery voltage).
Err, not quite. If the vehicle goes so fast that the back-emf exceeds the entire battery voltage, then indeed the vehicle will hit a speed wall and can't exceed it without regenerating back to the point where the battery voltage is not exceeded.

But in normal operation, that doesn't happen. Back to the DC case, it's when the back-emf exceeds the "transformed" battery voltage that regeneration will happen. At cruising speed, in a properly designed vehicle, this will be way lower than 100% of the battery voltage, so you have some head room to go faster.

Of course, for simplicity, I'm ignoring field weakening, which effectively reduces the motor's back-emf (but also torque) so that the motor can enter a relatively constant power region for most of its operating speeds (like >= ~50 mi/h).
2012 Leaf with new battery May 2019. New to me June 2019.
lorenfb
Posts: 2598
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Regen circuit questions

coulomb wrote: Fri Apr 22, 2022 4:03 am
lorenfb wrote: Thu Apr 21, 2022 3:13 pm ... one will notice the parallel diode within each of the six IGBTs, which gets forward biased when an EV enters its
re-gen mode (motor voltage greater than the battery voltage).
Err, not quite. If the vehicle goes so fast that the back-emf exceeds the entire battery voltage, then indeed the vehicle will hit a speed wall and can't exceed it without regenerating back to the point where the battery voltage is not exceeded.
The motor controller prevents that.
coulomb wrote: Fri Apr 22, 2022 4:03 am But in normal operation, that doesn't happen. Back to the DC case, it's when the back-emf exceeds the "transformed" battery voltage that regeneration will happen. At cruising speed, in a properly designed vehicle, this will be way lower than 100% of the battery voltage, so you have some head room to go faster.

Of course, for simplicity, I'm ignoring field weakening, which effectively reduces the motor's back-emf (but also torque) so that the motor can enter a relatively constant power region for most of its operating speeds (like >= ~50 mi/h).
Correct.
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 28K miles, SOH 105Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F
edoc
Posts: 6
Joined: Fri Apr 08, 2022 6:06 pm
Delivery Date: 09 Mar 2022
Leaf Number: 403221

Re: Regen circuit questions

Thanks guys for all the feedback....so with the complexities of the regen circuit .......
In my case of trying to feed additional external on board DC to the battery , looks like I will need to feed the battery directly somehow (after the "protection breakers")
RNeil
Posts: 20
Joined: Sun Jul 25, 2021 4:44 pm
Delivery Date: 25 Jul 2021

Re: Regen circuit questions

there isn't much in the circuit between the motor and the battery except the IGBT
This is a simplified schematic. There is a lot of stuff inside the IGBT block. There are six groups of insulated gate bipolar transistors (IGBTs). Each group has many IGBTs connected in parallel. The IGBT gates are connected to amplifiers called gate drivers. The gate drivers are connected to a microprocessor. The microprocessor has inputs for the accelerator position and the motor's encoder or position sensor. The microprocessor will determine the frequency, magnitude and phase of the three phase AC power needed for the motor. The phase can be adjusted to power the motor or make it regenerate. The current path for regeneration is the same as for accelerating.

I used to design electrical systems for electric fork lift trucks. The Leaf is similar to the newer AC forklift trucks.
goldbrick
Posts: 1726
Joined: Tue Aug 01, 2017 3:33 pm
Delivery Date: 01 Aug 2017
Leaf Number: 311806
Location: Boulder, CO

Re: Regen circuit questions

How different or similar is the inverter/driver on an EV compared to a basic permanent magnet DC brushless motor driver using 3 H-bridges? I've used those before but I thought there was more going on with an EV type motor.
lorenfb
Posts: 2598
Joined: Tue Dec 17, 2013 10:53 pm
Delivery Date: 22 Nov 2013
Leaf Number: 416635
Location: SoCal

Re: Regen circuit questions

goldbrick wrote: Wed May 18, 2022 11:33 am How different or similar is the inverter/driver on an EV compared to a basic permanent magnet DC brushless motor driver using 3 H-bridges? I've used those before but I thought there was more going on with an EV type motor.
The typical H-Bridge circuitry actually reverses the voltage to the stator to reverse the rotor direction,
where an EV PM motor controller (inverter) just changes the phases of the drive signals to reverse rotor direction.

https://electronics.stackexchange.com/q ... on-control
#1 Leaf SL MY 9/13: 76K miles, 47 Ahrs, 5.0 miles/kWh (average), Hx=70, SOH=73, L2 - 100% > 1000, temp < 95F, (DOD) > 20 Ahrs
#2 Leaf SL MY 12/18: 28K miles, SOH 105Ahrs/115Ahrs, 5.2 miles/kWh (average), DOD > 20%, temp < 105F

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