Controller and method for detecting a blocked state of an electrical machine

1. An electrical system comprising:

a brushless direct current motor;

a controller coupled to the brushless direct current motor and configured to:

determine a first power consumption of the brushless direct current motor while a first phase voltage for operating the brushless direct current motor at a first rotating field speed is applied to the brushless direct current motor,

determine a second power consumption of the brushless direct current motor while a second phase voltage for operating the brushless direct current motor at a second rotating field speed is applied to the brushless direct current motor,

calculate a power quotient between the first power consumption and the second power consumption,

compare the power quotient with a threshold value for the power quotient and output a comparison result, and

determine the brushless direct current motor is in the blocked state based on the comparison result thereby improving detection of the blocked state of the brushless direct current motor.

2. The electrical system as claimed in claim 1 , wherein the brushless direct current motor includes an inverter coupled to the controller and wherein the controller is further configured to determine an actual current consumption of the brushless direct current motor using a current sensor and the controller determines the first power consumption taking into account the actual current consumption determined by the current sensor and wherein the controller is further configured to determine a current consumption of the inverter driving the brushless direct current motor and the controller determines the second power consumption taking into account the current consumption of the inverter.

3. The electrical system as claimed in claim 1 , further comprising

a temperature sensor for determining a temperature of the brushless direct current motor and

the controller is further configured to determine the threshold value taking into account the temperature of the brushless direct current motor determined by the temperature sensor.

4. The electrical system as claimed in claim 1 wherein the brushless direct current motor has an inverter and the controller is further configured to generate a first control signal for operating the brushless direct current motor at the first rotating field speed and a second control signal for operating the brushless direct current motor at the second rotating field speed.

5. A drive, ventilation or air-conditioning system equipped with electrical system of claim 1 .

6. The electrical system as claimed in claim 1 , wherein the controller is further configured to abort a start-up process of the brushless direct current motor in response to the brushless direct current motor being in the blocked state.

7. The electrical system as claimed in claim 1 , wherein the controller is further configured to activate an energization scheme for releasing the brushless direct current motor from the blocked state in response to the brushless direct current motor being in the blocked state.

8. The electrical system as claimed in claim 1 , wherein the controller is further configured to:

increment an error memory in response to the brushless direct current motor being in the blocked state, and

decrement the error memory in response to the brushless direct current motor not being in the blocked state.

9. The electrical system as claimed in claim 2 , wherein the controller is further configured to determine a supply voltage for the brushless direct current motor using a voltage sensor and the controller determines the first power consumption taking into account the supply voltage determined by the voltage sensor and wherein the a voltage applied to the inverter for the brushless direct current motor and the controller determines the second power consumption taking into account the voltage applied to the inverter.

10. A vehicle having the drive, ventilation or air-conditioning system of claim 5 .

11. The electrical system as claimed in claim 6 , wherein the controller is further configured to continue the start-up process of the brushless direct current motor in response to the brushless direct current motor not being in the blocked state for a predetermined period of time.

12. The electrical system as claimed in claim 6 , wherein the controller is further configured to initiate an actual run-up process of the brushless direct current motor following the start-up process in response to the brushless direct current motor not being in the blocked state for a predetermined period of time.

13. The electrical system as claimed in claim 9 , wherein the controller is further configured to:

determine the first power consumption by multiplying the actual current consumption of the brushless direct current motor by the supply voltage determined by the voltage sensor, and

determine the second power consumption by multiplying the current consumption of the inverter by the voltage applied to the inverter.

14. An electrical system comprising:

a brushless direct current motor including an inverter coupled to the brushless direct current motor;

a controller including an inverter controller coupled to the inverter and configured to generate a first control signal for the inverter for operating the brushless direct current motor at a first rotating field speed and generate a second control signal for the inverter for operating the brushless direct current motor at a second rotating field speed;

the controller configured to:

determine a first power consumption of the brushless direct current motor while a first phase voltage for operating the brushless direct current motor at a first rotating field speed is applied to the brushless direct current motor,

determine a second power consumption of the brushless direct current motor while a second phase voltage for operating the brushless direct current motor at a second rotating field speed is applied to the brushless direct current motor,

calculate a power quotient between the first power consumption and the second power consumption,

compare the power quotient with a threshold value for the power quotient and output a comparison result, and

determine the brushless direct current motor is in the blocked state based on the comparison result thereby improving detection of the blocked state of the brushless direct current motor.

15. A method for detecting a blocked state of a brushless direct current motor of an electrical system including a controller coupled to the brushless direct current motor and configured to execute the following steps:

determining a first power consumption of the electrical machine while a first phase voltage for operating the brushless direct current motor at a first rotating field speed is applied to the brushless direct current motor;

determining a second power consumption of the electrical machine while a second phase voltage for operating the brushless direct current motor at a second rotating field speed is applied to the brushless direct current motor;

producing a power quotient between the first power consumption and the second power consumption;

comparing the power quotient with a threshold value for the power quotient and output a comparison result; and

determining the brushless direct current motor is in the blocked state based on the comparison result thereby improving detection of the blocked state of the brushless direct current motor.