Direct current machine with a controllable arrangement for limiting current

• US 20040104695A1
• Filed: 02/26/2003
• Published: 06/03/2004
• Est. Priority Date: 08/30/2000
• Status: Active Grant

• Current Assignee: Ebm-Papst St Georgen GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Original Assignee: Ebm-Papst St Georgen GmbH & Company KG (Ebm-Papst Mulfingen GmbH & Company KG)
• Inventors: Hahn, Alexander, Rappenecker, Hermann
• Granted Patent: US 6,825,632 B2
• Time in Patent Office: Days
• US Class Current: 318/254
• CPC Class Codes: F04D 27/004 by varying driving speed
• CPC Class Codes: H02P 6/28 Arrangements for controlling current H02P6/10 takes precedence

Abstract

An electronically commutated direct current machine comprising a rotor and a stator has a stator winding arrangement that can be supplied, via a full bridge circuit (78), with current from a direct current source (73, 74). A commutation arrangement (49, 50, 52, 54) is provided for commutating the semiconductor switches (1) (80 through 85) and is embodied in order, as a function of at least the position of the rotor (110), in a first bridge arm to switch on only one semiconductor switch in each case, and in a second bridge arm, controlled by a switching signal (PWM2), alternatingly to switch on and off a semiconductor switch associated with the switched-on semiconductor switch of the first bridge arm. Also provided is an arrangement for generating a switching definition signal (PWM1) which, by way of its magnitude, controls the pulse duty factor for the alternating switching on and off of the semiconductor switch associated with the first bridge arm. Also present is a current limiting arrangement (131, 161), controllable by means of a current target value signal (PWM_I+; PWM_I−), which, when a current specified by the current target value signal is reached in the direct current machine, modifies the switching definition signal in such a way that the current in the direct current machine becomes no greater than a limiting current that is specified by the current target value signal.

Claims

1. An electronically commutated direct current machine (32) comprising a rotor (110) and a stator (114),

comprising a stator winding arrangement (114) that can be supplied, via a full bridge circuit (78), with current from a direct current source (73, 74);

which full bridge circuit (78) comprises, in each bridge arm, an upper semiconductor switch that is connected to a positive line (73) and a lower semiconductor switch that is connected to a negative line (74);

comprising a commutation arrangement (49, 50, 52, 54) for commutating these semiconductor switches,

which commutation arrangement (49, 50, 52, 54) is embodied in order, as a function of at least the position of the rotor (110), in a first bridge arm to switch on only one semiconductor switch in each case, and in a second bridge arm, controlled by a switching signal (PWM2), alternatingly to switch on and off a semiconductor switch associated with the switched-on semiconductor switch of the first bridge arm;

and comprising an arrangement for generating a switching definition signal (PWM1) which, by way of its magnitude, controls the pulse duty factor for the alternating switching on and off of the semiconductor switch associated with the respective first bridge arm;

furthermore comprising a current limiting arrangement (131, 161), controllable by means of a current target value signal (PWM_I+;

PWM_I−

), which, when a current specified by the current target value signal is reached in the direct current machine, modifies the switching definition signal in such a way that the current in the direct current machine becomes no greater than a limiting current that is determined by the current target value signal.

2. The direct current machine according to claim 1,

wherein the commutation arrangement (49, 50, 52, 54) is embodied in order, as a function at least of the position of the rotor (110), in a first bridge arm to switch on only one semiconductor switch in each case, and in a second bridge arm, controlled by a switching signal (PWM2), alternatingly to switch on the upper and the lower semiconductor switch.

3. The direct current machine according to claim 1 or 2,

wherein the upper and lower semiconductor switches of the full bridge circuit (78) are embodied as MOSFET transistors.

4. The direct current machine according to one of the preceding claims,

wherein the current limiting arrangement (131, 161) influences the switching definition signal (PWM1) so that the driving current (i_2) in the stator winding arrangement (114) is limited to a first limiting current (I_max+), which first limiting current is controllable by means of a first signal (PWM_I+) conveyable to the current limiting arrangement (131, 161).

5. The direct current machine according to one of the preceding claims,

wherein the current limiting arrangement (131, 161) influences the switching definition signal (PWM1) so that a braking current (i_—

2′

) in the bridge circuit is limited to a second limiting current (I_max−

), which latter is controllable by means of a second signal (PWM_I−

) conveyable to the current limiting arrangement (131, 161).

6. The direct current machine according to one of the preceding claims,

wherein the current limiting arrangement (131, 161) influences the switching definition signal (PWM1) so that the driving current (i_2) in bridge circuit is limited to a first limiting current (I_max+) and so that the braking current (i_2′

) in the bridge circuit is limited to a second limiting current (I_max−

), the first limiting current (I_max+) and the second limiting current (I_max−

) being controllable respectively by means of first and second signals conveyable to the current limiting arrangement (131, 161).

7. The direct current machine according to one of the preceding claims, which comprises a controller (24) for regulating the rotation speed (n) to a specified rotation speed value (n_s), which controller (24) outputs a switching definition signal (PWM1) as a control input (n_CTRL via U_CTRL).

8. The direct current machine according to one of the preceding claims,

wherein the switching definition signal (PWM1) is adjustable to a value which substantially continuously activates the current limiting arrangement (131) that limits the driving current (i_2).

9. The direct current machine according to claim 8,

wherein the first signal (PWM_I+) controlling the first limiting current (I_max+) is adjustable to a specified value in order to generate a positive torque (T+) corresponding to the first limiting current (T_CTRL via I_CTRL).

10. The direct current machine according to claim 8, which comprises a controller (24) for regulating the rotation speed (n) to a specified rotation speed value (n_s), which controller (24) outputs as control input a first signal (PWM_I+) controlling the first limiting current (I_max+) (n_CTRL via I_CTRL).

11. The direct current machine according to one of the preceding claims,

wherein the switching definition signal (PWM1) is adjustable in such a way that the current limiting arrangement (161) limiting the braking current (i_2′

) is substantially continuously activated.

12. The direct current machine according to claim 11,

wherein the second signal (PWM_I−

) controlling the second limiting current (I_max−

) is adjustable to a specified value in order to generate a negative torque (T−

) corresponding to the second limiting current (I_max−

) (T_CTRL via I_CTRL).

13. The direct current machine according to one of the preceding claims, comprising a digital control element (23) serving for motor control, such as a microprocessor or microcontroller,

wherein the signal (PWM_I+ or PWM_I−

) conveyable to the current limiting arrangement (131, 161) is controllable by means of the digital control element (23).

14. The direct current machine according to claim 13,

wherein the switching definition signal (PWM1) is controllable by means of the digital control element (23).

15. The direct current machine according to one of the preceding claims, comprising an arrangement for monitoring the voltage (U_s) at the direct current source (73, 74), which arrangement blocks all the semiconductor switches of the full bridge circuit (78) when a specified upper limit value (U_MAX_OFF) of that voltage (U_s) is exceeded.

16. The direct current machine according to claim 15, comprising a digital control element (23) serving for motor control, such as a microprocessor or microcontroller, which comprises an A/D converter that converts the voltage (U_s) at the direct current source into a digital value (U_AD) for further processing in the digital control element (23).

17. The direct current machine according to one or more of the preceding claims, comprising a digital control element (23) serving for motor control such as a microprocessor or microcontroller, which, in operation, furnishes output signals for controlling the full-bridge circuit (78), each bridge arm having associated with it a commutation module (50, 52, 54) for alternatingly switching on its upper semiconductor switch and its and lower semiconductor switch, which commutation module comprises at least two signal inputs (e.g. IN1, EN1) that are controllable by means of separate signal outputs of the digital control element (23),

the PWM signal (PWM2) being conveyable to one of those signal inputs (IN1, IN2, IN3),

and a signal output (IN1, IN2, IN3), associated with that signal input, of the digital control element (23) being switchable into a high-resistance state in order to activate, from the digital control element, an alternating switching-on of the semiconductor switches of that bridge arm by means of the PWM signal (PWM2).

18. The direct current machine according to one or more of the preceding claims, comprising a digital control element (23) serving for motor control such as a microprocessor or microcontroller, which serves to regulate the rotation speed of the direct current machine and provides, at at least one output, a signal (PWM1) for influencing the rotation speed of the direct current machine,

and comprising an arrangement for limiting that signal to a rotation-speed-dependent value.

19. The direct current machine according to claim 18,

wherein that signal (PWM1) is limited, during the braking operation, to a value that decreases with decreasing rotation speed (n) of the direct current machine (32).

20. The direct current machine according to claim 18 or 19,

wherein that signal influences, by way of its pulse duty factor (PWM1), the charge state of a first capacitor (159);

furthermore a second capacitor (148) is provided which is connected via a resistor arrangement (150, 152) to the first capacitor (159); and

the pulse duty factor (PWM2) of the PWM signal conveyed to the full bridge circuit (78) is controlled substantially by the voltage at one of those two capacitors (148, 159).

21. The direct current machine according to claim 20,

wherein the second capacitor (148) has a lower capacitance than the first capacitor (159).

22. The direct current machine according to claim 20 or 21,

wherein a current limiting arrangement (131) is provided which, when limit value of the driving current specified by a current target value signal (PWM_I+) is exceeded, modifies the charge of that second capacitor (148) in order to limit the driving current to the current target value signal.

23. The direct current machine according to one of claims 20 through 22, wherein a current limiting arrangement (161) is provided which, when a limit value of the braking current (i_2′

) specified by a current target value signal (PWM_I−

) is exceeded, modifies the charge of that second capacitor (148) in order to limit the braking current to the current target value signal.

24. The direct current machine according to claim 22 or 23,

wherein the current limiting arrangement comprises a comparator for a comparison between a current target value signal (PHI1;

PHI2) and a pulsed signal (u_2;

u_2″

) derived from the driving current or braking current.

25. The direct current machine according to claim 24,

wherein the comparator has associated with it an integrating element (310, 312;

320, 322) in order to transform a pulsed current target value signal (PWM_I+;

PWM_I−

) into a smoothed signal (PHI1;

PHI2) for comparison to a pulsed current-dependent signal (u_2;

u_2″

).

26. The direct current machine according to one of the preceding claims, wherein

each upper transistor of a bridge arm has associated with it a storage capacitor (230) adapted to be charged via the lower transistor of that bridge arm and serving to supply that upper transistor with a control voltage;

comprising a commutation arrangement for commutating those transistors, which commutation arrangement is embodied in order, as a function at least of the position of the rotor (110), in a first bridge arm to switch on only one transistor and in a second bridge arm to switch on the upper and the lower transistor alternatingly,

the rotation speed (n) being monitored and, if it falls below a specified rotation speed value, and after a specified time has elapsed, the upper transistors of the full bridge circuit being briefly blocked and the lower transistors being switched on,

in order to charge the storage capacitors (230) of the upper transistors and thereby to ensure reliable control of those upper transistors even at low rotation speeds or if the direct current machine is at a standstill (FIG.

     24).

27. The direct current machine according to one of the preceding claims,

wherein the two transistors (80, 81) of a bridge arm each have associated with them a driver circuit (50, 52, 54) which can be enabled and disabled as a function of a first input signal (EN1) and which, in the disabled state, blocks both transistors (80, 81) of the respective bridge arm,

and which, as a function of a second input signal (IN1), in the state enabled by the first input signal (EN1) can be switched over in such a way that either the upper transistor (80) or the lower transistor (81) is made conductive,

furthermore comprising for control purposes a digital control element (23), such as a microprocessor or microcontroller, for generating the first input signal at a first output (EN1) and for generating the second input signal at a second output (IN1), and

comprising a third input signal (80) in the form of a PWM signal having a controllable pulse duty factor (PWM;

PWM2), which third input signal is conveyable from a PWM signal source (182) to the driver circuit (50) in parallel with the second input signal (IN1) and is effective only when the second output (IN1) of the digital control element (23) is switched into a specified switching state.

28. The direct current machine according to claim 27,

wherein the specified switching state of the second output (IN1) of the digital control element (23) is a high-resistance state (TRISTATE).

29. The direct current machine according to claim 27 or 28,

wherein the third input signal (180) is conveyed to the driver circuit (50, 52, 54) via a diode (260).

30. The direct current machine according to one or more of claims 27 through 29,

wherein the amplitude of the third input signal (180) is limited, in particular by means of a Zener diode (186).

31. The direct current machine according to one or more of claims 27 through 30,

wherein the driver circuit has an input (223) to which is connected a resistor (252) whose magnitude influences the magnitude of a dead time (Δ

t) upon switchover between the transistors (80, 81) of the associated bridge arm,

and that resistor (252) can be at least partially bypassed by means of a controllable switching element (250) that is controllable by the first input signal (EN1).

32. The direct current machine according to claim 31,

wherein the controllable switching element (250) is controlled into a specified switching state when the first output (EN1) of the digital control element (23) assumes a high-resistance state, in order thereby to block the associated bridge arm (80, 81).

33. The direct current machine according to one or more of claims 27 through 32,

wherein the pulse duty factor (PWM2) of the PWM signal source (182) is controllable by means of the voltage at a capacitor (148), which voltage, when too high a driving current is flowing in the stator winding arrangement, is modifiable in a specified direction by means of a first current limiting arrangement (131), so that that driving current is lowered by way of a corresponding modification of the pulse duty factor (PWM2),

and, when too high a braking current is flowing in the stator winding arrangement, is modifiable by means of a second current limiting arrangement (161) in a direction opposite to the specified direction, in order to lower the braking current by way of a corresponding modification of the pulse duty factor (PWM2).

34. The direct current machine according to claim 33,

wherein a limiting apparatus for the pulse duty factor (PWM2) is provided in order to prevent the lower transistor (81) of a bridge arm from being constantly open, and the upper transistor (80) constantly closed, in the presence of an extreme value of the pulse duty factor (PWM2).

35. The direct current machine according to one or more of claims 27 through 34, which has at least three phases and comprises at least three activation circuits (50, 52, 54) for the bridge arms (21, 22, 23);

and

comprising an arrangement (FIG.

     31) which, during a commutation, prevents an interruption of the first input signal (EN1) of a driver circuit if that driver circuit must be enabled before and after the commutation.

36. Use of a direct current motor according to one of the preceding claims to drive a fan.

37. The use according to claim 36,

wherein the fan is operated at substantially constant driving current.

38. The use according to claim 36 or 37,

wherein the direct current motor has a plurality of phases.

39. The use according to claim 38,

wherein a full bridge circuit is provided for supplying current to the phases.

40. The use according to one of claims 36 through 39,

wherein the fan is embodied as a diagonal or radial fan.

41. The use according to claim 40,

wherein a rotation speed controller is provided for the direct current motor (32);

and a monitoring arrangement (672) is provided which, during operation of the fan (370) at a specified rotation speed, monitors the motor current and

generates an alarm signal (FIG.

     38) when a specified current value is exceeded.

42. The use according to claim 41,

wherein the rotation speed controller is embodied in such a way that it generates, as the control input for setting the rotation speed, a current target value for a current controller of the direct current motor (32),

and that current target value is monitored in order to generate the alarm signal when a specified value is exceeded.

43. The use according to one of claims 36 through 42,

wherein a rotation speed controller for the direct current motor is provided, also a switching and measuring apparatus which encompasses an automatic shutoff of the direct current motor after attainment of a specified first rotation speed, a time measurement for the elapsed time between shutoff and the attainment of a specified second rotation speed, and an evaluation apparatus for evaluation of that elapsed time.

44. The use according to claim 43,

wherein the evaluation apparatus is embodied in order to generate an alarm signal if the elapsed time falls below a specified value.

45. The use according to one of claims 36 through 44,

wherein the fan is embodied as a diagonal or radial fan;

furthermore, current is supplied to the direct current motor via a current controller that is set to a specified current;

furthermore, an apparatus for sensing the rotation speed of the direct current motor is provided;

and an alarm apparatus is provided which generates an alarm signal when a specified value of that rotation speed is exceeded.