Method for adjusting an inverter connected to an electric motor via a du/dt filter
The method for adjusting an inverter ( 1 ) connected to an electric motor ( 2 ) via a du/dt-filter ( 3 ) and a motor cable ( 4 ) is described. The method comprises the steps of generating a pulse on the motor cable by means of the inverter ( 1 ) measuring a cycle time of a pulse answer from consecutive current peaks, determining a time delay t d from the cycle time, determining a dwell time T dwell to be avoided from the time delay t d by T dwell =k*t d , k ∈ {2, 6, 10, . . . } adjusting the time between consecutive switchings of the inverter ( 1 ) to be out of a range from T dwell −t A to T dwell +t A wherein t A is an allowable deviation from T dwell .
1. A method for adjusting an inverter connected to an electric motor via a du/dt filter and a motor cable comprising the steps of
generating a pulse on the motor cable by means of the inverter
measuring a cycle time (T OSC ) of a pulse answer from consecutive current peaks,
determining a time delay t d from the cycle time,
determining a dwell time T dwell to be avoided from the time delay t d by
T dwell =k·t d , k∈{ 2,6,10, . . . }
adjusting the time between consecutive switchings of the inverter to be out of a range from T dwell −t A to T dwell +t A wherein t A is an allowable deviation from T dwell .
2. The method according to claim 1 , wherein the pulse is at least so long as to generate two consecutive reflected current peaks.
3. The method according to claim 1 , wherein the generated current is measured by the inverter.
4. The method according to claim 1 , wherein
t A <2* t d *p
wherein p is a factor depending on a width of the first pulse of the pulse answer, and/or on k.
5. The method according to claim 1 , wherein the allowed dwell time T dwell is stored in a look-up table.
6. The method according to claim 1 , wherein the pulse is generated by closing a first switch in a first phase (U) and a second switch in a second phase (V) of the inverter.
7. The method according to claim 6 , wherein the first switch and the second switch are closed at the same time.
8. The method according to claim 6 , wherein at the end of the pulse generation the first switch is opened at a first time and the second switch is opened at a second time different from the first time.
9. The method according to claim 8 , wherein a difference between the first time and the second time is in a range from 40 to 80 μs.
10. The method according to claim 2 , wherein the generated current is measured by the inverter.
11. The method according to claim 2 , wherein
t A <2* t d *p
wherein p is a factor depending on a width of the first pulse of the pulse answer, and/or on k.
12. The method according to claim 3 , wherein
t A <2* t d *p
wherein p is a factor depending on a width of the first pulse of the pulse answer, and/or on k.
13. The method according to claim 2 , wherein the allowed dwell time T dwell is stored in a look-up table.
14. The method according to claim 3 , wherein the allowed dwell time T dwell is stored in a look-up table.
15. The method according to claim 4 , wherein the allowed dwell time T dwell is stored in a look-up table.
16. The method according to claim 2 , wherein the pulse is generated by closing a first switch in a first phase (U) and a second switch in a second phase (V) of the inverter.
17. The method according to claim 3 , wherein the pulse is generated by closing a first switch in a first phase (U) and a second switch in a second phase (V) of the inverter.
18. The method according to claim 4 , wherein the pulse is generated by closing a first switch in a first phase (U) and a second switch in a second phase (V) of the inverter.
19. The method according to claim 5 , wherein the pulse is generated by closing a first switch in a first phase (U) and a second switch in a second phase (V) of the inverter.
20. A non-volatile computer readable medium encoded with a computer program for adjusting an inverter connected to an electric motor via a du/dt filter and a motor cable, the computer program comprising computer executable instructions for controlling a programmable processor to:
generating a pulse on the motor cable by means of the inverter,
measuring a cycle time (T OSC ) of a pulse answer from consecutive current peaks,
determining a time delay t d from the cycle time,
determining a dwell time T dwell to be avoided from the time delay t d by
T dwell =k*t d , k∈{ 2,6,10, . . . },
adjusting the time between consecutive switchings of the inverter to be out of a range from T dwell −t A to T dwell +t A wherein t A is an allowable deviation from T dwell .