JPH036747B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A field reversible type reversible Leonard device is composed of a speed control loop having an armature current minor loop and a field control loop for field reversal, and the present invention relates to an improvement of the field control loop. It is.

Conventionally, the field control loop detects the armature voltage and performs automatic field weakening control so that the armature voltage becomes a certain constant value, but during steady operation, the armature voltage polarity is constant regardless of the rotation direction. , the polarity is reversed only during deceleration operation, so if the rotation direction is switched, the armature voltage will become a positive feedback and the polarity must be reversed. Therefore, after setting the armature voltage to the same sign, it is necessary to convert it to positive or negative depending on the polarity of the field current and then feed it back. Various devices for issuing positive and negative commands, etc., and a gate circuit for zeroing the armature current while switching the field current were also required, making these control devices quite complex and inconvenient to handle.

SUMMARY OF THE INVENTION In order to alleviate the above-mentioned drawbacks, it is an object of the present invention to provide a field reversible type reversible Leonard device that has a simple and inexpensive structure for the field control loop and provides stable control.

The present invention will be explained below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention, which is roughly divided into a speed control circuit and a field current control circuit.

On the speed control side with an armature current minor loop, 1 is a speed command, 2 is a PI regulator with saturation for speed control, 3 is a current transformer, 6 is a rectifier, 7 is a PI regulator for armature current control, and 8 is a PI regulator with saturation for controlling the armature current. Thyristor driver, 11
is the speed detector.

On the other hand, on the field control side for field reversal, 13 is a comparator with a polarity discrimination function, 14 is a PI regulator with saturation for controlling back electromotive force, and 15 is for controlling field current.
PI controller, 16 is thyristor driver for forward rotation
TDF, 17 is reversing thyristor driver TDR,
18 is a back electromotive voltage detector, 19 is a field current detector,
Comparator CPR that turns “ON” when 20 is reversed;
Comparator CPF that turns “ON” when 21 rotates forward;
25 is a rectifying means. 4 and 5 are switch elements
ESR and ESF, ESR closes contact 4a of the speed control circuit and contact 4b of the back electromotive force feedback circuit during reverse rotation, and ESF also closes contacts 5a and 5 during forward rotation.
Let b be closed. Further, 22, 23, and 26 are code converters, and 31 is a positive bias power supply. 12 is a short-circuit switch for preventing the integral element of the speed control saturating PI regulator 2 from producing an output even when the input is zero, and 24 is a first-order delay circuit for increasing the stability of the system. In addition, the main thyristor 9, motor armature 10, field coil 29, forward rotation thyristor SCR _F 27, and reverse rotation thyristor SCR _R 28 are included in the armature circuit and field circuit of the motor.

FIG. 2 is a time chart for explaining the operation. In the same figure, A is the speed command V _S from the speed command device, C is the armature current F detected via the current transformer 3 and rectifier 6, B is the motor rotation speed N,
D is the back electromotive force command B from the comparator 13, E is the back electromotive voltage V _M from the back electromotive voltage detector 18, and F is the back electromotive force made to have the same sign by the rectifier 25.
V _M 1, G is a reverse feedback voltage feedback signal C that is fed back via the switch element ES _R 4 or ES _F 5, 4 is a back electromotive voltage control by comparing and detecting the back electromotive voltage command B and the back electromotive force feedback signal C. field current command D amplified by the PI regulator 14 with saturation, ri is the field current feedback signal I _f detected by the field current detector 19, nu is the output of the forward rotation switch element ES _F 5, is the output of the reverse switch element ES _R 4, time t ₁ to _{t 2} indicates stop, t ₂ to _{t 3} indicates normal rotation, t ₃ to _{t 4} indicates reverse rotation, and after t ₄ represent the time of deceleration, respectively.

FIG. 3 is a graph showing changes in back electromotive force V _M and field current I _f with respect to motor speed N.

Next, the operations of stopping, forward rotation, reverse rotation, and deceleration of the electric motor will be explained with reference to FIGS. 1, 2, and 3.

1 When the motor is stopped, both the _t1 to _t2 speed command V _S and speed feedback signal V _N are zero,
Further, the switch 12 is kept "ON" in order to prevent the error from expanding due to the integral element of the speed control saturating PI regulator 2. The armature side input becomes zero,
On the field side, since the input to the comparator 13 is zero V, the back electromotive force command B is saturated either positive or negative, but here it is assumed that it is saturated negative.
Since the back electromotive voltage feedback signal C is zero V, the saturation PI regulator 14 for controlling the back electromotive voltage saturates in the positive direction, and the field current command D reaches its maximum value in the positive direction, so the reversing thyristor driver TD _R 17 operates, and the reversing thyristor SCR _R 28 turns “ON”.
Constant current control is performed in the opposite direction with the field fully strengthened. Since the field current feedback signal If becomes _negative , an output is generated in the reversal comparator CP _R 20, and the reversing switch element ES _R 4 is turned "ON".

2 When the motor rotates forward, turn the switch 12 ``OFF'' from _t2 to _t3 . If the speed command V _S is given in a stepwise manner at time t ₂ , since V _N is zero V, the output of the speed control saturating PI regulator 2 becomes negatively saturated. On the armature side, since _ESR 4 is "ON", contact 4a is closed, current command E is zero, and main thyristor 9 is not operating. On the field side, the comparator 13 becomes positively saturated, the back electromotive force command B is reversed and becomes positive, the field current command D becomes negative, the forward rotation thyristor driver TD _F operates, and the forward rotation thyristor SCR _F 27 turns "ON". , the field _current If flowing in the opposite direction is reversed to the positive direction. The field current I _f is established to a certain value in the positive direction (time t ₂ ′)
An output is generated in the forward rotation comparator CP _F21 , the forward rotation switch element ES _F5 turns "ON", and the armature side receives the current command E and starts up. The motor is linearly accelerated by voltage control until the motor speed reaches the base speed N _p , and since the back electromotive force feedback amount C is smaller than the back electromotive voltage command B, a saturation regulator for back electromotive voltage control is used. 14, the field current command D continues to be saturated, and the field current _If reaches its maximum in the positive direction. At time _t2 '', when the speed reaches N _p and the back electromotive force V _M reaches the specified maximum value V _MO , the back electromotive voltage feedback amount C becomes approximately equal to the back electromotive force command B, and the field current command D reaches saturation. After that, automatic field weakening control is performed to reduce the field _current If so that the back electromotive force V _M becomes the specified value V _MO .
When the motor speed further increases and the speed feedback amount V _N becomes close to the command speed V _S , the speed deviation decreases, the PI regulator with saturation for speed control 2 is released from saturation, the armature current command E becomes small, and the armature The motor speed is controlled to the command speed by the current minor loop.

That is, until the motor speed reaches the base low speed N _p , the field current I _f is a constant value of full strength field, and the speed is controlled by the armature voltage, and after the base low speed N _p , the armature voltage increases. It is controlled by automatic field weakening control that reduces _the field current If to a constant value.

3 When the motor is reversed t ₃ - _{t 4} The speed command V _S is reversed, so the speed deviation becomes the negative maximum value, and the output A becomes the positive saturation value, so the armature current becomes zero because contact 4a is open. Become. On the other hand, the back electromotive voltage command B is reversed to negative, and the back electromotive voltage feedback signal C is also negative while the contact 5b is closed, so the polarity of the field current command D is reversed, and the field current that was flowing in the positive direction I _f also reverses and increases in the negative direction based on the command D, and ES _F5 is set to “OFF”.
Turn ES _R4 “ON”. During this time, the armature current F of the motor is zero, so no braking torque is generated and the speed hardly changes. When ES _R 4 turns "ON", contact 4a is turned on and armature current command E is given, and the armature current F flows to perform regenerative braking and reduce the speed due to the action of the armature current minor loop, and as the motor speed decreases, the reverse occurs. Based on the electromotive voltage command B, the field is strengthened to maintain the back electromotive voltage V _M at the specified maximum value V _MO ,
At time t ₃ ', when the base speed N _p is reached, the operation signal of the saturation PI regulator 14 for controlling back electromotive force becomes equal to or higher than a certain value, and the field current command D is saturated.
Thereafter, the motor linearly decelerates under voltage control under a constant field current, and eventually the speed reaches zero, reverses, accelerates, and reaches the opposite base speed -N _p (time t ₃ ''). After -N _p , the motor speed reaches the command speed. is controlled by automatic field weakening control so that the back electromotive voltage remains at a constant value.

4 After motor deceleration t ₄ When a deceleration command as shown in Figure 2 A is given at time t ₄ , the deceleration deviation becomes positive and the output A of the speed control saturation PI regulator 2 changes from positive to negative. Since the rotation is reversed, the operation of each part is the same as in the case of the reverse speed command explained in the previous section 3, but at the time when the motor speed decreases to below the command speed (time t ₄ ')
Then again output A of PI controller 2 with saturation for speed control.
is reversed and becomes positive, armature current F once becomes zero, back electromotive force command B reverses to negative, and then ES _F
5 is turned "OFF" and ES _R4 is turned "ON", and the command speed is maintained by voltage control under a constant field current of the full field strength in the opposite direction. In addition, in the case of an emergency stop, turn on switch 12 and use saturation for speed control.
Even if the output of the PI regulator 2 is set to zero and the armature side is turned OFF, the back electromotive voltage command B remains unchanged on the field side, and the field current I _f also remains at a constant value, resulting in dynamic braking.

The structure and operation of the present invention have been described above. The feature of the present invention is that the speed deviation signal is converted into a certain positive or negative fixed value according to the signal by a comparator having a polarity discrimination function. A constant voltage is used as a back electromotive voltage command, and the back electromotive voltage detection circuit is equipped with a rectifier to convert the detected back electromotive voltage into a signal of the same sign. each with a separate switch element that operates above a certain field current;
These switch elements and a sign converter provided in one switch element convert the polarity of the back electromotive voltage across the rectifier according to the direction of the field current, so that the polarity of the back electromotive force applied to the rectifying means is always changed regardless of whether it is in a steady state or a transient state. Negative feedback is provided for the back electromotive voltage command, and the armature current is also set to zero between the different polarities of the speed deviation signal and field current using the above comparator and switch elements. Compared to conventional devices, the structure is simpler and cheaper, and the control characteristics are more stable.

In the embodiment, the back electromotive voltage was detected as the detection voltage, but there is no difference in effect even if the motor terminal voltage is used.In other words, it is sufficient to detect the armature voltage.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention;
FIGS. 2 and 3 are a time chart and a graph, respectively, for explaining the operation. 4...Switch element ES _R for reverse rotation, 5...Switch element ES _F for forward rotation, 13...Comparator with polarity discrimination function, 14...Saturation for controlling back electromotive force
PI controller, 18... Back electromotive voltage detector, 25...
Rectifying means, 23, 26... code converter.

Claims (1)

[Claims] 1. In a field-reversing type reversible Leonard device, a speed deviation signal is converted into a fixed value armature voltage command by a comparator having a polarity discrimination function, and the armature voltage is controlled by a rectifying means in its feedback circuit,
Once converted into a signal of the same sign, the signal is switched in the direction of the field current via a switch element that closes with a field current of more than a certain value in the forward or reverse direction and has a sign converter on either side. The polarity is determined accordingly and matched against the armature voltage command, forming an armature voltage control loop that always provides negative feedback, and forming a minor loop of the field current using the armature voltage deviation signal as the field current command value. A reversible Leonard device with magnetic field reversal.