Motor controller

Details Motor controller Motor controller

2000-07-11

2001-11-06

Masih, Karen (Department: 2837)

Electricity: motive power systems

Limitation of motor load, current, torque or force

C318S798000, C318S801000, C318S806000, C318S800000, C318S812000, C318S807000

Reexamination Certificate

active

06313593

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a motor controller, and in particular to a motor controller which is used as a drive source of various machines such as machine tools, industrial equipments, and robots, and in which feedback control of a drive current for driving a motor is conducted.
2. Description of the Prior Art
In a motor controller which detects a current flowing through a motor and which utilizes the detected current for current control of the motor, the detected motor current is converted into a unit which can be readily utilized for control, such as voltage, with a certain conversion ratio, and then utilized. Furthermore, in the motor controller, there is provided a function of detecting an overcurrent and interrupting the motor current, in order to protect a permanent magnet motor from destruction caused by demagnetization in the case where the control is disabled or in the case where switching power elements are subjected to short mode destruction.
FIG. 2
is a block diagram of a principal part of a motor controller for effecting feedback control of this motor current. Reference numeral
10
denotes an inverter circuit for generating AC power of an arbitrary frequency from a DC power source E. In this inverse circuit
10
, diodes D
1
to D
6
are connected parallel to switching elements T
1
to T
6
formed of power elements such as IGBTs, in the reverse direction, respectively, forming 6 sets of parallel circuit. Further, these 6 sets of parallel circuits (T
1
-D
1
; T
2
-D
2
; . . . T
6
-D
6
) are arranged 3 sets of series connections each composed of two parallel circuits. And these 3 sets of series connections are connected in parallel to the DC power source. Moreover, a connection point between 2 sets of parallel circuits which constitute a set of series connection is connected to one of U, V and W phases of a motor.
A current flowing through each phase winding is detected by a current detector
20
, and converted to a unit which is easy to be used for control of voltage or the like. This converted voltage is fed back to current control means
40
. On the basis of a current command and the detected current value thus fed back, the current control means
40
effects current feedback control, and outputs a PWM generation signal to PWM signal generation means
60
. On the basis of the PWM generation signal, the PWM signal generation means generates a PWM signal which turns on/off the switching elements T
1
to T
6
of the inverter circuit
10
.
Furthermore, an overcurrent detection circuit
50
is provided to the motor controller. If a signal obtained by converting a current detected by the current detection means
20
to a voltage exceeds a preset level, then the overcurrent detection circuit
50
outputs a signal to the PWM signal generation circuit
60
and thereby inhibits a PWM signal output from the PWM signal generation circuit
60
.
As described above, the current detection means
20
converts the detected current value to an easily usable voltage and outputs the voltage. The conversion ratio between the current and voltage in the current detection means is fixed in the prior art. On the other hand, it is desirable that the signal converted from current into voltage has a dynamic range wide as far as possible in order to stabilize the motor control.
For example, in a motor which is at least 50 A in motor demagnetization limit current, the current detection means
20
in the controller converts a commanded maximum current 40 A to a voltage 4 V, and an overcurrent protection voltage (i.e., a voltage at which output of the PWM signal is inhibited and the switching elements are turned off) is set to 5 V. In
FIG. 2
, this example is shown, and a full range for current control is set to 4 V and an overcurrent detection level is set to 5 V.
On the other hand, in a motor which is at least 100 A in motor demagnetization limit current, an commanded maximum current 80 A is converted to a voltage 4 V, and an overcurrent protection voltage is set to 5 V (5 V×80 A/4 V=100 A).
In the prior art motor controller, the conversion ratio to voltage or like in the current detection means is fixed. In addition, the conversion ratio is determined on the basis of conditions of the motor maximum current and the motor demagnetization limit current. Accordingly, there occur restrictions in the combination of the motor controller and the motor.
Especially, in the case of a multi-shaft controller in which one motor controller drives and controls a plurality of motors, there is a problem of an increased number of necessary machine kinds (current detection means differing in conversion ratio).
SUMMARY OF THE INVENTION
The object of the invention is to alleviate restriction in combination of a motor controller and a motor which will be caused by a conversion ratio with which a current detected by a motor current detector is converted into a unit (such as voltage) easily usable in motor current control.
The present invention relates to a motor controller which comprises switching elements for controlling currents flowing through windings of a motor, current detection means for detecting current flowing through the windings of the motor, and current control means for generating a control signal of the switching elements on the basis of a current command and an output of the current detection means. And in the present invention, there is newly provided conversion ratio alteration means capable of selecting and altering a conversion ratio with which a detection signal detected by the current detection means is converted to an input signal of the current control means. As a result, restrictions imposed on the combination of the motor and the controller are lightened. Furthermore, there is provided means which compares an output of the current detection means with a predetermined value, and when a current value of at least one phase has exceeded the predetermined value, the means turns off the switching elements. The motor and the controller are thus protected.
The conversion ratio which the conversion ratio alteration means output may be automatically altered on the basis of information supplied from the motor, automatically altered on the basis of a command given by a host controller, or altered on the basis of a preset switch.
Furthermore, conversion means for converting a detection signal detected by the current detection means into a signal to be inputted to the current control means may be mounted between the current detection means and the current control means so as to be freely exchangeable and so as to conform to the motor.
The current detection means may output a detected current value as an analog voltage, a digital value, or a pulse train. The conversion ratio alteration means converts the output signal to an input signal of the current control means with the selected conversion ratio.
In the present invention, the conversion ratio to be used when converting the current value detected by the current detection means to an easy usable unit can be selected and altered. Accordingly, motors of different kinds can be driven and controlled by one controller. Therefore, restrictions imposed on the combination of the motor and the controller are reduced. Furthermore, since one motor controller suffices, handling and management become easy in manufacturing, distribution, and maintenance. There are brought about merits in various aspects.


REFERENCES:
patent: 5504517 (1996-04-01), Takashi et al.
patent: 5569995 (1996-10-01), Kusaka et al.
patent: 5917319 (1999-06-01), Frank et al.
patent: 63-085404 (1988-05-01), None
patent: 2-53291 (1990-02-01), None
patent: 2-280700 (1990-11-01), None
patent: 3-124290 (1991-05-01), None
patent: 6-121442 (1994-04-01), None
patent: 7-16549 (1995-07-01), None
patent: 7-327382 (1995-12-01), None
patent: 10-221382 (1998-08-01), None

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