Elektroroller-Forum.de

dominik hat geschrieben: Sa 19. Aug 2023, 16:29 The motor will pull 680A because these Motors have near zero resistance.
My 5kW 60V motor pulls easily the 600pA the Fardriver provides. But it heats up quite fast.

Thanks Dominik, great to hear that. Then my calculations (divising max phase current limit by 3 phases) are wrong but at least I got further
What I do not understand is
1. should we count power from line amps or from phase amps x voltage ?
2. stupid question but for sure - controller does not change voltage, does it ? I have to google how controller makes more phase amps from line amps (transformator or something similar ?).
3. why my motor does not pull more phase amps even when reaching max line current ? I know, it does not need it so it does not pull it so it depends on controller settings and/or on line current limit.
4. what is the relation between line current and phase current ? I mean is my controller even able to make 400A phase current from 130A line current ??? According to your saying yes so what am I missing ???
Can you share your field weakening settings ? Thanks !

You can't count power at all.
You can only see how much power is drwan from the battery.
This power has to be multiplied with the efficiency value from the controller and again multiplied with the efficiency value from the motor and then you will have power at the rear wheel.

For example
Controller efficiency 95%
motor efficiency 85%
250bA x 84V = 21kw from the battery
21kw 0,95x0,85= 17kW at the rear wheel
And 4kW heat. 1kW at the controller and 3kW heat to heat the motor.

2. Controller does change voltage from DC to AC and reduces the AC voltage to the value you need to get your desired phase current. It works like a frequeny inverter or a smps

3. The controller reduces the voltage so that it does not exceed his rated phase or line current, otherwhise the mosfets would die very fast

4. There is no real relation between line and phase current.
The controller can put out 400pA at low rpm when you climb a hill.
I have measured the set 630Phase amps from my controller. If I set more phase amps acceleration gets slower because the controller overshoots above his save Operation area and reduces the current way to much and then it starts to raise the phase amps again , and repeats this over and over again. You can Herr and feel this Regulation. You can see the reduction of the line current during the start from a standstill as a die in the dank blue line, this line should raise until the set max line value and then it should rest there until the motor reaches top speed.
This could be better with the right ki and kp settings. your motor does handle higher voltages. With more volts it can spin faster and draw more current during acceleration , but it will get warmer when you accelerate faster or drive faster

dominik hat geschrieben: Sa 19. Aug 2023, 17:34 2. Controller does change voltage from DC to AC...

So our BLCD hub motor are AC, not DC ? I read a lot about it and found both sayings. I does not makes sense to me as sellers (QS etc.) usually says motor voltage "72V".

Excelent explanation, thank you. So controller works like an fotovoltaic convertor, this is what I understand a little bit. But still - it can not make more kW than it gets from battery ? I mean for example 72V x 130A = 9,36kW goes into controller and controller change it to (for example) 300A phase amps, that means around 30V ???

The current waveform looks like AC

I have measured my SVMC72150 with a rogowski current transducer and an oscilloscope

This measured 250A are the same as the advertised 350Apeak from Sabvoton.
The most Controller manufacturers advertise the peak phase current. [Sevcon not)
The peak is the highest point of the sinewave. It is calculated Ipeak= Ixsqrt(2)
250Ax1,41=353Apeak

Motor power is calculated
P=U x I x sqrt(3)
U is Ubattery/sqrt(2)

80V/1,41=56V
So max RMS Voltage the controller can make is 56V without losses.
When the controller makes 80A phase current at full speed you get 56Vx80Ax1,73=7700W
Battery current is then somewhere around 100 to 110A.

Miguello80 hat geschrieben: Sa 19. Aug 2023, 18:46 ...
So our BLCD hub motor are AC, not DC ?
...

As our moderator MEroller already mentioned, the abbreviation BLDC, for a stand alone motor, is completely misleading.
There is no thing like a brushless motor, driven just by plain direct current.
As soon as you have to switch or alternate the field activating currents, AC comes into play.

So, over all, a so called "BLDC" is a complete integrated (brushless) unit of motor, controller & sensors that you can feed with dc.

Talking about phases and/or phase currents is absolutely nonsens for DC.

The better description for our hub motor is: permanent magnet synchrounus motor -> PMSM.

jeff-jordan hat geschrieben: Sa 19. Aug 2023, 20:08 Talking about phases and/or phase currents is absolutely nonsens for DC.

Thanks Jeff. You are right, I have already looked up info about PMSM and (mine) IPMSM.
I am asking because I need to decide what controller to buy - quality promising 3shul C350 rated 200A/400A or standard 72530/72680 (72680 fits my factory controller dimensions = holes). Question is - can I use more than 400A phase ? Than 72680. I am not sure whether factory phase wires (4 AWG I guess) will handle that. I would not be the first guy who would try it but I do not want to fry the motor.

You can use 600A phase current in the liw rpm range to get a better acceleration from a standstill. Above you have to reduce phase current.
My 5kW60V motor had AWG6 wires and I melted them uphill while drawing 20kw for a länger period.
If your motor has a temperature sensor the controller will reduce power when the temperature goes over 140°C at 155°C it only give 1/4 the power you could draw when the motor is cold.

Hey hey,

Bei meiner heutigen Fahrt ist meine eine Bremse ausgefallen - man konnte den Hebel einfach, ohne Widerstand, komplett durchdrücken. Beim nächsten Versuch hat sie wieder funktioniert. Und so ging es einige Male. Mein erster Gedanke war: Luft im Bremssystem. Das war aber nie offen und nach Sicht ist auch nirgends Flüssigkeit ausgelaufen. Und auch sonst konnte ich keine Auffälligkeiten an der Bremse feststellen. Hatte jemand schonmal das selbe Problem? Bremsen sind ja jetzt nicht das irrelevanteste Teil

Grüße, Al