sudden changes in the speed are not getting controlled

Hi Shruthi

If you see a fixed time in between the stop and restart, it is possible that the motor get locked first because of one of the lock conditions tripped when received the sudden change command.

Our expert will get back to you early next week.

Best regards,

Thank you for the reply

when changing the speed suddenly from low to high and high to low lock0 is getting enabled and motor is not adapting to the sudden changes in the speed.

i have tried disabling current limit lock but it is not working

Thank you

Shruthi,

You have to properly configure, Before start-up setting on basic page and lock detection current thershold on advance setting page.

Please share the GUI images of these two pages. Also, let me know following for your motor:

1.         Motor resistance phase to center tap    -   

2.         Velocity constant; V/Hz    -   

3.         Rated voltage and rated speed at rated voltage

4.     rated current  at rated speed-

5.         Number of pole -

Best Regards

Milan

Hi Sir,

Thank you  for the reply.

please  find the attachments and data

1.      1.5 Ohms

2.       509mV/Hz

3.        24V,340RPM

4.        1.5A@340RPM

5.        16poles

with the above configuration motor is rotating however sudden changes in the speed it is not adapting to it(FULL SPEED to OFF and then ON it immediately),i tried disabling current limit lock, changing the lock detection current threshold and disabling acceleration  current limit but the problem persisting .

Pl kindly suggest how to tune it.

Thank you

Shurthi, Try following:1. Reduce the close loop accelerate to minimum.
2. disable acceleration current limit and keep the lock detection to maximum 3.2 amp.
3. Reduce the align time to minimum.
4. Enable initial speed detect and keep thersold as 6Hz, similar to above picture.
BTW how are you doing speed changes via EVM POT or via GUI speed command.
Best RegardsMilan-Motor Applicaiton Team

Hi,

i have done the above settings but  the problem still persisting

testing the speed through EVM POT .

Thank you

Shurthi,

Sudden change in motor speed as fast as POT changes the speed command will not be practically feasible due to following reason:

1. Very fast deceleration from high speed to low speed, can cause very high voltage at VCC because of motor mechanical energy pumping back to VCC. To prevent damage against over-voltage DRV10983 has Anti-voltage surge protection, which reduces the motor deceleration rate. You may try disabling it to get fast deceleration but be careful because it can charge VCC beyond 30V, damaging device.
2. Similarly, close loop acceleration will prevent fast acceleration, you may try to increase it but very high rates will hit over-current faults.

Both of above parameter is highly depended motor inertia and electric time constants. In summary for given motor with above constrain, only limited range of acceleration/deceleration ramp is possible.

Best Regards

Milan-Motor Application Team

Our end application is ceiling fan ,how can we fix this problem ,do we need to change the design of motor?with drv10983 can we go for production ?
Pl kindly suggest.
Thank you

Shruthi,

For ceiling fan application, very fast speed changes are not at all required. Typically, for this segment speed ramp time are in 10of sec, like fo reaching from zero to full speed in 20 or 30 secs, similarly speed reduction from full speed to min would also be in 20 or 30secs. With proper acceleration setting, your motor should be able to meet these requirements. I don't expect motor change.

With proper testing from your side, for all worst case scenarios you should be able to take DRV10983 based solution to production.

Best Regards

Milan-Motor Application Team

hi ,

 i have tried changing the parameters and below are the observations

1.speed changes in closed loop checked with gui speed command 

2.even in open loop on,off  conditions current limit lock is getting enabled

3. tried changing accelerate current limit,closed loop accelerate ,lock detection threshold

conclusion in the observations

        sequence of actions       Motor state              STATUS

                          1                          OFF                       STATIONARY

                          2                         ON                           Accelerating 

                          3                         OFF                         decelerating

                         after few min   ( In off state motor speed has reached to nearly to 100RPM)

                           4                        ON                            LOCK0

 If the speed in off state is 100RPM(nearly some  where around) in that stae it if i on the motor it is getting locked ,but if the speed is in off state is more than certain RPM (say 100) in this case on the motor there is no problem it is able to catch up the speed input

why we are stressing this point because in microchip (which is also sensor-less ) ,it is working perfectly for the speed changes which currently  am doing with the TI EVM.

i hope if it is the tuning issue am sure it wont be much complex to solve .

Thank you in advance

Shruthi,

DRV10983 have resynchronization feature to get smooth start-up from already sppinning motor. You should be able to tune it. Try following setting:

1. Disable acceleration current limit, keep the lock-detection thershold to maximum 3.2Amp.

2. 100 rpm for 16-pole motor means ~ 13.3Hz, so set Initial speed detect therhold to 6Hz and enable Initial speed detect.

3. Just for initial tuning for time being, de-select all lock detection fault.

you should be able to get resynchronization with above setting.

Best Regards

Milan-Motor Application Team

1.disabled acceleration current  limit and kept lock-detection threshold to maximum 3.2Amp

2.before i have setted  Initial speed detect threshold to 6Hz and enable Initial speed detect but still at lower rpm if i on the motor it was getting locked.

3. de-selected all lock detection faults

but no change :-(

more over my current sensing resistor has blown away ,i think because of disabling all locks apart from that no damage  to the EVM !

Today i checked enabling IPD settings there is not much difference!!

 

shruthi,

Sorry about this, hope you are able to bring back the board to original condition.

BTW are you using EVM or your own custom board, becuase EVM does not current sense resistor? Also can you tell me, how are you performing on/off sequence when motor is running at 100 rpm? Are you doing on/off of input power supply or making it via GUI, in which case 24V remains on always?

 

Best Regards

Milan-Motor Application Team

 placed 1ohm resistor of half watt in series to W phase just to check the phase current on scope,but there is a provision given in EVM to sense current R13 i didnt use it anyway.i will cut the trace and use it from now on.

so far i didn't check direct power supply on/off,am doing through GUI using pot and i2c speed command  and also without gui using pot(standalone mode written the registers to EEPROM) in the sense all the tests  have done with 24V is always  ON.

how are you performing on/off sequence when motor is running at 100 rpm

100 rpm when motor is in off state means motor is decelerating in this case supply  24v  is ON ,speed command is zero(pot,i2c)

Shruthi,

1ohm shunt resistor is quite big value; it can add error in comparators used for back-emf zero crossing for re-synchronization from existing speed. I would suggest you to remove it and tune the re-synchronization, as I per setting mentioned in my previous post.

Please share the phase voltage and current waveforms, during this condition for us to understand the issue better.

Best Regards

Milan-Motor Application Team

Here am attaching wave forms of phase current  ,phase to phase voltage i put 0.3ohms resistor in series to phase w