openinverter forum

Hi all. I'm running my tests : version 4.65.R-sine, opmode start 1, battery 38 V, motor Ansaldo 30/60 kW.
For some reason the engine starts to accelerate at potnom values less than -30 %.
I hope someone knows what I've done wrong. Seppo

Hi Johannes,

I've added some potnom/speed-plots with different param values.
In all cases, the change in speed works the opposite of what it should
at a certain braking value.
The motor starts and accelerates smoothly at the positive values but
it starts to accelerate at high braking values and even at lower values
at higher speeds.

Could you please give me a hint what to make in a different way?

Seppo

Hmm, numimp looks plausible, that is often a culprit when motors misbehave. Still you could check the pulse count with a scope.
How does it work in manual mode for positive and negative fslipspnt? Are you using a V1 main board that does not support AB encoder?

I'm using the V2 main board and a single Chanel encoder connected to pin 3.
I tested the encoder and it looks working ok. 1000 rpm on the plot diagram is almost
same as 1000 Hz from the encoder (numimp 64, chA).
Positive values in manual mode worked perfectly. Negative fslipspnt values acted as zero.
When the encoder was connected the motor starts and continues accelerating.
Hope you have ideas....

Here are the pictures of my main board and the changes of the schema.
I'm wondering if it is meant to be a short circuit between pins PA6/TIM3_CH1 and PD2/TIM3_ETR
as is seems to be in the case of a single channel encoder?

Your parts on the main board are alright. You no longer need the connection "J1" but it doesn't hurt. Something is wrong with your numimp, negative fslipspnt MUST yield regen. Please concentrate on your encoder - data sheet or scope.

Manual mode measurements.

I tryed once again the transition from 20 to 3 and the transition from 20 to -20.
For some reason the negative values of fslipspnt don't work. The negative values act alike zero.

Then I made some measurement from the pin GTOP of the driver board.
It seems like the parameter fmin limits the function of fslipspnt. Manual mode stops working at values less than fmin.

Am I barking the wrong tree?

Good news, now the regen works. I had wrong specs of the encoder.
Number of pulses per revolution is 80, not 64 as I was told.
I am still a little confused why the manual mode didn't work at negative
fslipspnt values. But all the same thank you for your patience.

The fmin sets a minimum allowed frequency, so it's no surprise that fslipmin isn't allowed to go below that
Fmin should usually be as low as possible, Johannes planned to make it a hidden parameter. Leave it at 0.2 and you should be fine.

If you want to do regen in manual mode, just flip it into reverse and apply positive slip.

Yes I deleted fmin in the most recent versions and internally set it to 0.2 or something.
Ok, 64 instead of 80 is a huge error! It means that one physical rotation is counted as 1.25 rotations. 64 Hz rotor speed is measured as 80 Hz so you were always applying huge positive slip! If rotor speed is measured as 80 Hz (in place of 64 Hz) and you seemingly apply -2 Hz slip, you are applying 80-2=78 Hz which is actually 14 Hz POSITIVE slip