The inverter can be adapted to many kinds of motors, battery packs and driver preferences by changing parameters.
The parameters to adjust the inverter to the motor are boost, fweak, fslipmin, fslipmax, polepairs, fmin, fmax and numimp.
They can be deduced from the motors nameplate or by trying which feels best. For illustration we will assume a bus voltage of 500V and a 4-pole (p=2) motor with a nominal speed of n=1450rpm@f=50Hz and 230V. With 500V DC an AC voltage of 500/1.41=355V can be generated.
boost is the digital amplitude of the sine wave at motor startup. It is needed to overcome the motors ohmic resistance. Digital amplitude is an internal quantity. 0 means no voltage is generated at all, 37813 means the full possible voltage is generated.
At full throttle an effective voltage of 1700/37813*355=16V is generated. The best way to find a feasible value is to optimize it in the finished car. Start with the default value and increase until you get a good startup.
fweak is the frequency at which the full possible voltage is generated. It is also the point of the highest motor power. Beyond fweak torque will decrease to the square of frequency and thus power will decrease linear with frequency.
A starting point for fweak is the motors nameplate:
With our illustration motor fweak=355/230*50=77Hz. fweak can be configured lower than that resulting in more torque at the low end.
fslipmin/fslipmax is the slip frequency at which the motor is run at minimum/maximum throttle. fslipmin is set to the motors optimal slip frequency which can be deduced from the nameplate. fslipmin=f-p*n/60. With our illustration motor fslipmin=50-2*1450/60=1.66Hz. fslipmax can be set as high as breakdown torque which is not found on the nameplate. So its best found experimental starting with 2*fslipmin. If set too high the motor will start to rock violently on startup, possibly tripping the over current limit.
polepairs is set to p, 2 in our example.
fmin should be set just below fslipmin.
fmax is used to limit the speed of the motor. The default 200Hz would result in a maximum speed of about 6000rpm.
ampmin Is the minimum relative amplitude fed to the motor. At very low amplitudes the motor does not generate any noticable torque and throttle travel is wasted that does nothing. Find out a good value by experimenting.
pwmfrq Sets the frequency at which the IGBTs are switched on and off. The faster the switching the higher the losses in the inverter and the lower the losses in the motor. The maximum frequency is also limited by the driver boards as explained here.
pwmpol Sets the polarity of the PWM signals, active high or active low. Do not touch this parameter if you don't know what you're doing. When configured inversely it will blow up your power stage immediatly if connected to a potent power source like batteries.
deadtime The time between switching off one IGBT and switching on the other. 28=800ns, 63=1.5µs. More values can be found in the STM32 data sheet. Make sure to test the deadtime at low power levels. Setting the deadtime too low while operating of a potent power source can blow up your power stage!
The following parameters currently exist to customize the controller software. Type
to change it. Type
to get the current value.
Parameters are internally stored with 5 binary fraction digits. That means there are 32 possible values after the decimal point. So when you set a value of 0.35 you might end up with 0.33.
|boost||dig||0||37813||1700||0 Hz Boost in digit. 1000 digit ~ 2.5%|
|fweak||Hz||0||400||67||Frequency where V/Hz reaches its peak|
|udcnom||V||0||1000||0||Nominal voltage for fweak and boost. fweak and boost are scaled to the actual dc voltage. 0=don't scale|
|fwkp||0||10000||1||Inverter MTPA (maximum torque per amp) gain|
|frqfac||dig/Hz||-10000||10000||10||PI controller help to reach appropriate output at higher frequencies. 0=No Help|
|fpconst||Hz||0||400||400||Frequency where slip frequency is derated to form a constant power region. Only has an effect when < fweak|
|fslipmin||Hz||0||100||1||Slip frequency at minimum throttle|
|fslipmax||Hz||0||100||3||Slip frequency at maximum throttle|
|polepairs||1||16||2||Pole pairs of motor (4-pole motor: 2 pole pairs)|
|respolepairs||1||16||1||Pole pairs of resolver|
|encflt||0||16||4||Filter constant between pulse encoder and speed calculation. Makes up for slightly uneven pulse distribution|
|encmode||0||4||0||0=single channel encoder, 1=quadrature encoder,
2=quadrature /w index pulse, 3=SPI (deprecated) 4=Resolver
|fmin||Hz||0||400||1||Below this frequency no voltage is generated|
|fmax||Hz||0||400||200||At this frequency slip is commanded 0 to avoid further acceleration|
|numimp||Imp/rev||8||8192||60||Pulse encoder pulses per turn|
|dirchrpm||rpm||0||2000||100||Motor speed at which direction change is allowed|
|dirmode||0||1||1||0=button (momentary pulse selects forward/reverse), 1=switch (forward or reverse signal must be constantly high)|
|syncofs||dig||0||65535||0||Phase shift of sine wave after receiving index pulse|
|syncadv||dig/Hz||-100||100||0||Shifts "syncofs" downwards/upwards with frequency|
|snsm||2||3||2||Motor temperature sensor. 2=KTY83, 3=KTY84|
|pwmfrq||0||3||2||PWM frequency. 0=17.6kHz, 1=8.8kHz, 2=4.4kHz, 3=2.2kHz. Needs PWM restart|
|pwmpol||0||1||0||PWM polarity. 0=active high, 1=active low. DO NOT PLAY WITH THIS!
Needs PWM restart
|deadtime||dig||0||255||28||Deadtime between highside and lowside pulse. 28=800ns, 56=1.5µs. Not always linear, consult STM32 manual. Needs PWM restart|
|ocurlim||A||-65535||65535||100||Hardware over current limit. RMS-current times sqrt(2) + some slack|
|minpulse||dig||0||4095||1000||Narrowest or widest pulse, all other mapped to full off or full on, respectively|
|il1gain||dig/A||0||4095||4.7||Digits per A of current sensor L1|
|il2gain||dig/A||0||4095||4.7||Digits per A of current sensor L2|
|udcgain||dig/V||0||4095||6.15||Digits per V of DC link|
|udcofs||dig||0||4095||0||DC link 0V offset|
|udclim||V||0||1000||540||High voltage at which the PWM is shut down|
|snshs||0||1||0||Heatsink temperature sensor. 0=JCurve, 1=Semikron|
|bmslimhigh||%||0||100||50||Positive throttle limit on BMS under voltage|
|bmslimlow||%||-100||0||-1||Regen limit on BMS over voltage|
|udcmin||V||0||1000||450||Minimum battery voltage|
|udcmax||V||0||1000||520||Maximum battery voltage|
|iacmax||A||0||5000||5000||Maximum peak AC current|
|ifltrise||dig||0||32||10||Controls how quickly slip and amplitude recover. The greater the value, the slower|
|ifltfall||dig||0||32||3||Controls how quickly slip and amplitude are reduced on over current. The greater the value, the slower|
|idcmax||A||0||5000||5000||Maximum DC input current|
|idcmin||A||-5000||0||-5000||Maximum DC output current (regen)|
|chargemode||0||4||0||0=Off, 3=Boost, 4=Buck|
|chargecur||0||50||0||Charge current setpoint. Boost mode: charger INPUT current. Buck mode: charger output current|
|chargekp||0||100||80||Charge controller gain. Lower if you have oscillation, raise if current set point is not met|
|chargeflt||0||10||8||Charge current filtering. Raise if you have oscillations|
|chargemax||%||0||99||90||Charge mode duty cycle limit. Especially in boost mode this makes sure you don't overvolt you IGBTs if there is no battery connected.|
|potmin||dig||0||4095||0||Value of "pot" when pot isn't pressed at all|
|potmax||dig||0||4095||4095||Value of "pot" when pot is pushed all the way in|
|pot2min||dig||0||4095||4095||Value of "pot2" when regen pot is in 0 position|
|pot2max||dig||0||4095||4095||Value of "pot2" when regen pot is in full on position|
|potmode||0||2||0||0=Pot 1 is throttle and pot 2 is regen strength preset,
1=Pot 2 is proportional to pot 1 (redundance) 2=Throttle controlled via CAN
|throtramp||%/10ms||0||100||100||Max positive throttle slew rate|
|throtramprpm||rpm||0||20000||20000||No throttle ramping above this speed|
|ampmin||%||0||100||10||Minimum relative sine amplitude|
|slipstart||%||10||100||50||% positive throttle travel at which slip is increased|
|brknompedal||%||-100||0||-50||Foot on break pedal regen torque|
|brkpedalramp||%/10ms||1||100||100||Ramp speed when entering regen. E.g. when you set brkmax to 20% and brkpedal to -60% and brkpedalramp to 1, it will take 400ms to arrive at brake force of -60%|
|brknom||%||0||100||30||Regen padel travel|
|brkmax||%||0||100||30||Foot-off regen torque|
|brkout||%||-100||-1||-50||Activate brake light output at this amount of braking force|
|brkrampstr||Hz||0||400||10||Below this frequency the regen torque is reduced linearly with the frequency|
|idlespeed||rpm||-100||1000||-100||Motor idle speed. Set to -100 to disable idle function. When idle speed controller is enabled, brake pedal must be pressed on start.|
|idlethrotlim||%||0||100||50||Throttle limit of idle speed controller|
|idlemode||0||1||0||Motor idle speed mode. 0=always run idle speed controller, 1=only run it when brake pedal is released, 2=like 1 but only when cruise switch is on|
|speedkp||Hz||0||100||1||Speed controller gain (Cruise and idle speed). Decrease if speed oscillates. Increase for faster load regulation|
|cruisemode||0||1||0||0=button (set when button pressed, reset with brake pedal), 1=switch (set when switched on, reset when switched off or brake pedal)|
|speedflt||dig||0||16||1||Filter before cruise controller|
|udcsw||V||0||1000||330||Voltage at which the DC contactor is allowed to close|
|udcswbuck||V||0||1000||540||Voltage at which the DC contactor is allowed to close in buck charge mode|
|tripmode||0||2||0||What to do with relays at a shutdown event. 0=All off, 1=Keep DC switch closed, 2=close precharge relay|
|pwmfunc||0||2||0||Quantity that controls the PWM output. 0=tmpm, 1=tmphs, 2=speed|
|pwmgain||dig/C||0||65535||100||Gain of PWM output|
|pwmofs||dig||-65535||65535||0||Offset of PWM output, 4096=full on|
|canspeed||0||3||0||Baud rate of CAN interface 0=250k, 1=500k, 2=800k, 3=1M|
|canperiod||0||1||0||0=send configured CAN messages every 100ms, 1=every 10ms|
|fslipspnt||Hz||-100||100||0||Slip setpoint in mode 2. Written by software in mode 1|
|ampnom||%||0||100||0||Nominal amplitude in mode 2. Written by software in mode 1|
The following values are available for diagnostic purposes. Type
to get the current value. To read more then one you can provide a list like
|opmode||Operating mode. 0=Off, 1=Run, 2=Manual_run, 3=Boost, 4=Buck, 5=Sine, 6=2 Phase sine|
|udc||V||DC link voltage|
|uac||V||Calculated AC voltage|
|idc||A||Calculated DC current|
|il1||A||AC current L1|
|il2||A||AC current L2|
|il1rms||A||RMS current L1|
|il2rms||A||RMS current L2|
|boostcalc||A||DC link adjusted boost setting|
|fweakcalc||A||DC link adjusted fweak setting|
|amp||dig||Sine amplitude, 37813=max|
|pot||dig||Pot value, 4095=max|
|pot2||dig||Regen Pot value, 4095=max|
|potnom||%||Scaled pot value, 0 accel|
|dir||Rotation direction. -1=REV, 0=Neutral, 1=FWD|
|uaux||°C||Auxiliary voltage (i.e. 12V system). Measured on pin 11 (mprot)|
|din_cruise||Cruise Control. This pin activates the cruise control with the current speed. Pressing again updates the speed set point.|
|din_start||State of digital input "start". This pin starts inverter operation|
|din_brake||State of digital input "brake". This pin sets maximum regen torque (brknompedal). Cruise control is disabled.|
|din_mprot||State of digital input "motor protection switch". Shuts down the inverter when =0|
|din_emcystop||State of digital input "emergency stop". Shuts down the inverter when =0|
|din_ocur||Over current detected|
|din_bms||BMS over voltage/under voltage|
|cpuload||%||CPU load for everything except communication|
First you want to find a flat surface - a parking lot etc. so you can drive and stop without checking traffic. Change only one parameter at a time and save settings that work!
1. set fslipmin so that you feel car taking off smoothly and try to change it by +/-0,1Hz and check differences in starting. Save when satisfied.
2. lower boost value in 100 point until motor jitters at start. Then return it to last good value.
3. try lowering ampmin in 0,1 increments and observe throttle travel. When throttle is not just smooth but becomes sluggish return some previous increments until throttle reaction is acceptable.
4. change fweak value in +/-10Hz increments from starting point and observe torque in starting. This value is very dependent on battery voltage and is very subjective.
Now you find a hill or ramp and set car on it. You want to hold car in position on slope just using throttle pedal. If there parameters are not good motor will jump or will feel sluggish
1. add boost if motor is oscillating if it is smooth reduce it in 100 point increments until you get oscillation. Then return to last good value
2. reduce/increase ampmin in 0,25 increments untill you get oscilation in motor and return last good value
Now set the car into a hill to set fslipmax. Warning full throttle will be used. Be sure there is no other traffic!
Set fslipmax to chosen value (guess it at 2xfslipmin if you have no other way) and try to take off with full throttle.
If car feels sluggish with full throttle you have to add more slip.
If motor starts to jitter there is too much slip. Try to reduce it in 0.1Hz increments.
When you feel satisfied with settings save them and go on setting regen and braking effect.