Problem w/ Temp Sensor MXUS 3k Sabvoton

hias9

1 kW
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Jul 11, 2018
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Hi everybody,

Today I started connecting my MXUS 3K v3 (3T) to my Sabvoton SVMC72150.
Swapped green and yellow phase and Hall cables and set Pn to 23. Hall angle test worked fine.
I plan to run it at 20 or 21S, but for the moment I am testing with a 48V (13S) battery.

For the moment there are two issues:

1) I have a Sabvoton with a white cable for the temp sensor which I have connected to the white temp sensor cable of the MXUS. It should be a KTY83/110 sensor.
The problem is that the value for motor temperature is always around -35 to -40 degrees.

2) At 54V battery voltage and without flux weakening, the highest no-load rpm I have seen in the Sabvoton app was 588 which is a bit low I think. kv is 11.9 for my 3T, so it should be aroud 640 at 54V which I can only achieve with some flux weakining. Do you think this is normal or could there be a problem?
 
When you can’t achieve the no load speed of a motor, of course there is a problem. Could be as simple as ´you ordered a 3t but they shipped a 4t’, or as quick as ‘your throttle doesn’t return full speed voltage signal’...

But, there is a problem, and it shouldn't be very long to troubleshoot.
 
Throttle voltage is fine (5V). Sabvoton is configured to give a full throttle signal if throttle voltage is >4.4V, so that is not the problem.
I have seen the rpm increase by about 20% when connecting the high-speed cable to 0V, however a few minutes later I realized that it was just because flux weakening got switched on by doing that.

For a 4T (kv 8.9) rpm seem too high.
 
hias9 said:
1) I have a Sabvoton with a white cable for the temp sensor which I have connected to the white temp sensor cable of the MXUS. It should be a KTY83/110 sensor.
The problem is that the value for motor temperature is always around -35 to -40 degrees.
What kind of sensor is the Sabvoton expecting?

The KTY83 is a PTC resistance sensor:
https://www.nxp.com/docs/en/data-sheet/KTY83_SER.pdf
and would read around 570-600ohms or so at the indicated temperature. What resistance does it read with a multimeter when disconnected from the controller, when the controller just read that temperature range?


Also, does the Sabvoton read the sensor wired signal and ground, or does it read signal and voltage?

I'm testing a controller at the moment that requires +V on one sensor wire, and the sensor signal on the other wire, no ground. (a ground shorts out the controller).
 
According to the seller, the Sabvoton is for a KTY83/110.

Resistance from white controller cable (disconnected) to 0V is 10.88kohms.
Resistance from white motor cable (disconnected) to 0V is 566ohms.
Resistance to voltage is >100kohms and not stable (decreasing).

By the way, is it normal that no-load-rpms are lower on a sinewave controller (with flux weakening disabled) than on a square wave controller?
 
I found a 480ohm resistance and put it in series. Now temp sensor says 32 when motor is standing still. With the motor turning it is 23-30. Real temp should be around 25 degrees Celsius.
By the way, with a 1kohm resistance it says 90 with motor standing still.

Is it normal that the temp sensor gives around 5-7 degrees lower values when turning?
 
There's a chart you can google for the KTY sensor's resistances at various temperatures, so you can verify if it's reading correctly (not connected to the controller).

If it is, then the controller is reading the sensor wrong, and you'd either have to program it to do it right if tha'ts possible, or send it back to the seller or manufacturer for warranty repair / replacement.

The sensor will give the same reading regardless of motor turning or not, if the temperature is the same.

If the controller reads something different, then something is wrong with it or the wiring.
 
It is fine with a resistance around 450 Ohm in series. One sensor reads around 545 and the other around 575 Ohms at about 25 degrees Celsius.

I now switched to the second set of halls and temp sensor of the MXUS. This one shows more stable values when the motor is turning. It is always around 3-4 degrees lower when the motor is turning (without load) compared to the motor standing still, but that should not be a problem for me.
 
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