Method for operating an electric motor
View Patent ↗A method and device for determining the motor moment constant k M of an electric motor by measuring motor parameters on the running motor. For reduction of the previously considerable measuring effort it is proposed that firstly the generator voltage U EMK produced by the motor is measured, and in that the motor moment constant k M is calculated by division of the generator voltage U EMK and the speed of rotation f Mot of the motor, taking into consideration at least one further constant. The method and the device are suitable for DC motors and for 3-phase synchronous motors.
1. A method for determining properties of an electric motor by measuring motor parameters of the electric motor, comprising:
accelerating the electric motor to a speed of rotation f Mot by applying an operating voltage;
after the accelerating step, switching off the operating voltage;
after the step of switching off the operating voltage, allowing an inductive operating current of the motor to fade away;
after the step of allowing the operating current to fade away, determining a generator voltage U EMK produced by the electric motor as the electric motor rotates, and determining the speed of rotation f Mot ; and
determining a motor torque constant k M for the electric motor using the produced generator voltage U EMK and speed of rotation f Mot .
2. A method according to claim 1 , wherein the motor comprises a DC motor, and wherein the determining step comprises calculating the motor torque constant k M according to the following formula:
k
M
=
U
EMK
2
π
·
f
Mot
3. A method according to claim 2 , wherein the motor comprises a 3-phase synchronous motor, and wherein the determining step comprises calculating the motor torque constant k M according to the following formula
k
M
=
U
EMK
2
π
·
f
Mot
·
3
4. A method according to claim 1 , wherein the step of determining the generator voltage U EMK comprises determining the generator voltage with essentially no current flowing through the electric motor.
5. A method according to claim 1 , further comprising, after the accelerating step, determining the speed of rotation f Mot .
6. A method according to claim 5 , wherein the motor is a DC motor, and wherein the step of determining the speed of rotation f Mot comprises measuring the speed of rotation f Mot via an external speed of rotation measuring device.
7. A method according to claim 5 , wherein the motor is a 3-phase synchronous motor, and wherein the step of determining the speed of rotation f Mot comprises measuring a cycle duration of the generator voltage U EMK .
8. A device for determining properties of an electric motor by measuring motor parameters of the electric motor, comprising:
(a) means for accelerating the electric motor to a speed of rotation f Mot , comprising means for applying an operating voltage;
(b) means for switching off the operating voltage and allowing an inductive operating current of the motor to fade away; and
(c) means for determining a generator voltage U EMK produced by the electric motor as the electric motor rotates at the speed of rotation f Mot and after the operating current fades away;
(d) means for determining the speed of rotation f Mot of the rotating motor; and
(e) a computer configured to receive results from both determining means and to calculate a motor torque constant k M from the results.
9. A device according to claim 8 , wherein the device is configured to determine the generator voltage U EMK when the motor rotates at the speed of rotation f Mot .
10. A device according to claim 9 , wherein the motor comprises a DC motor, and wherein the computer is further configured to calculate the motor torque constant k M according to the following formula.
k
M
=
U
EMK
2
π
·
f
Mot
11. A device according to claim 9 , wherein the motor comprises a 3-phase synchronous motor, and the computer is further configured to calculate the motor torque constant k M according to the following formula.
k
M
=
U
EMK
2
π
·
f
Mot
·
3
12. A device according to claim 8 , wherein the means for determining the generator voltage U EMK comprises means for determining the generator voltage with essentially no current flowing through the electric motor.
13. A device according to claim 8 , further comprising means for determining the speed of rotation f Mot after the motor has been accelerated.
14. A device according to claim 13 , wherein the motor is a DC motor, the device further comprising an external speed of rotation measuring device.
15. A device according to claim 13 , wherein the motor is a 3-phase synchronous motor, and wherein the means for determining the speed of rotation f Mot of the motor comprises means for measuring a cycle duration of the generator voltage U EMK .