JPS634433B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a DC/DC switching converter that performs switching control on the primary side of a transformer and performs thyristor rectification on the secondary side in order to make a DC stabilized power supply smaller and more efficient. This paper relates to an electric motor drive system that applies

Conventional motor drive systems require a DC tachogenerator because the motor current flows continuously and it is difficult to detect the induced voltage, and current detection feedback is required because the current control lag is large.

Therefore, as the first conventional example without DC tachogenerator or current detection feedback,
Publication No. 159508 can be seen.

In this first conventional example, the secondary side of the output transformer for driving the electric motor includes only a diode and a filter, and the switching is performed only on the primary side of the output transformer.

Furthermore, as a second conventional example of this type,
There is a publication No. 47-27321.

The second conventional example does not use an output transformer to drive the motor.

Therefore, these conventional examples do not have a DC/DC/switching converter that performs switching control on the primary side of the transformer and rectifies the thyristor on the secondary side of the transformer. However, it was not possible to make the motor compact and drive the electric motor with high efficiency.

The advantage of this DC/DC switching converter is that the transformer, switching transistor, filter, etc. operate at high frequencies or with small currents, making the device compact.

FIG. 1 shows a diagram of the principle of the present invention. S is a commercial AC power supply, DS is a rectifier diode, C is a smoothing capacitor, D _P , D _N are feedback diodes, TF is a transformer, L
is a reactor, M is a DC motor, and Th _F and Th _R are thyristors.

Now, transistors T _rp and T _rN are turned on at the same time and turned off at the same time. Thyristor Th _F is turned on when motor M outputs forward rotation torque, and thyristor Th _R is turned on when motor M outputs reverse rotation torque.

If T is the carrier period, the transistors T _rP and T _rN are always on for T/2 seconds and off for T/2 seconds at a period of T seconds. these transistors
The switch circuit consisting of T _rp and T _rN is designed to open and close at a constant cycle T seconds within a range that does not saturate the transformer TF. When transistors T _rP and T _rN are turned off,
The excitation current of the transformer TF is fed back to the capacitor C on the power supply side via the diodes _DP and _DN .

FIG. 2 is a waveform diagram of the motor current when the motor is running, and FIG. 3 is a waveform diagram of the motor current when the motor is braking. Here, power running means that current flows against the motor induced voltage, so that the motor M functions as an electric motor, and braking means that current flows in the same direction as the motor induced voltage, so that the motor M functions as a generator.

To drive motor M, select either thyristor Th _F or Th _R at time t ₁ between 0 and T/2,
Trigger that gate. t ₂ is the point in time when the motor current becomes zero.

Here, during power running, T/2 - t ₁ > t ₂ - T/2, so no matter where the firing time t ₁ is between 0 and T/2, the time t ₂ will never exceed the period T. (t ₂ <
T, Figure 2).

However, during braking, T/2 - t ₁ < t ₂ - T/2, so when the firing time t ₁ approaches T/2, t ₂ > T
It may become.

When t ₂ > T, the thyristor Th _F or Th _R
keeps firing and becomes uncontrollable.

As a control to prevent this, the induced voltage of motor M is e _M ′ (positive during braking), the primary and secondary voltages of transformer TF are E ₁ and E ₂ , and the primary and secondary windings of transformer TF are number of lines
Assuming W ₁ and W ₂ , E ₂ = E ₁ ×W ₂ /W ₁ , but for the ignition time t ₁ , t ₁ > T・e _M ′/(E ₂ +e _M ′), and the ignition time It is sufficient to control t ₁ within the range of T·e _M ′(E ₂ +e _M ′)<t ₁ <T/2.

This is due to the following reason.

In this circuit, that is, the motor, reactor, and transformer secondary winding, the leakage inductance is L, the resistance is R, and L/R>>T, and the resistance R is ignored.

(T/2−t ₁ )(E ₂ +e _M ′) = (t ₂ −T/2)(E ₂ −e _M ′) holds, so t ₂ −T/2=(T/2−t ₁ )(E ₂ +e _M ′)/(E ₂ −e _M ′)<T/2 Therefore, t ₁ >T/2 {1−(E ₂ −e _M ′)/(E ₂ +e _M ′)} That is, t ₁ > T・e _M ′/(E ₂ +e _M ′). Therefore, 360°×e _M ′/(E ₂ +e _M ′) is the critical minimum firing angle.

Therefore, if the ignition time t ₁ is controlled within these conditions, the motor current will always be intermittent.

Since the terminal voltage of the motor M directly indicates the induced voltage e _M (positive during power running) when the motor current is zero, the induced voltage e _M can be easily detected. This is used to determine the ignition time _t1 . Furthermore, in speed control of a motor with a permanent magnet field, the induced voltage e _M is proportional to the speed, so this can be used as a speed signal, so a DC tachogenerator is not required.

Next, feed forward control of motor M will be described.

The following relationship exists between the firing time t ₁ of the thyristors Th _F and Th _R and the motor current average value _M.

T/2−t ₁ ≒ √ ₂・(1+e _M /E ₂ )・√ _M Here, e _M is the motor induced voltage with the power running time being positive.

In other words, t ₁ ≈T/2−√ ₂ ·(1+e _M /E ₂ )·√ _M By performing this calculation, the ignition time t ₁ is determined.

This is derived as follows.

Assuming L/R≫T, ignoring the resistance R, and setting the maximum value of the motor current as I _M , (T/2- _t1 )( _E2 - _eM ) = ( _t2 -T/2)( _E2 +e _M )=L I _M t ₂ -t ₁ = (T/2-t ₁ )+(t ₂ -T/2) = (T/2-t ₁ )(1+E ₂ -e _M /E ₂ +e _M ) = (T/2-t ₁ )・2E ₂ / (E ₂ + e _M ) _M = 1/2I _M (t ₂ − t ₁ )/T = 1/2・1/L (T/2-t ₁ ) ² E ₂ (E ₂ −e _M )/
(E ₂ +e _M )1/T Therefore (T/2-t ₁ ) ² = LT/E ₂・_M・(E ₂ +e _M /E ₂ −e _M and (e _M /E ₂ ) ² ≪1 T/2−t ₁ √ ₂・(1+e _M /E ₂ )・√ _M is obtained.

FIG. 4 is a block diagram of one embodiment of the present invention, FIGS. 5 and 6 are partially detailed views thereof, and FIG. 7 is a time chart showing the operation of each part.

In Fig. 4, 1 is a speed deviation amplifier, which has a speed command voltage 9 and an induced voltage that is the equivalent speed of the motor M.
e _M is divided into appropriate voltages, subtracted and amplified by a speed error amplifier, and used as a current command signal for motor M.
This is because, as described above, no current flows through the motor M immediately before the thyristors Th _F and Th _R are fired, so the induced voltage e _M can be detected.

2 is a timing (period T) generation circuit, which generates a 180° energizing square wave using the control circuit's reference clock (a type of carrier), and generates a 180° energizing square wave to
For base drive of T _rP and T _rN and thyristor
It provides a reference point for the firing angle control circuit 5 for Th _F and Th _R.

3 and 4 are base drive circuits, which isolate and amplify the signal from the control circuit signal level and drive the bases of the transistors T _{rP and} T _rN of the transformer primary winding drive, and consist of a pulse transformer, photocoupler, etc. There is.

Reference numeral 5 denotes a firing angle control circuit which, as mentioned above, generates the thyristor trigger pulse t ₁ after t ₁ with the rising point of the timing generation circuit 2 as a reference, and at the same time generates the F/signal (high For forward rotation drive at LOW, and reverse rotation drive at LOW, only the polarity of the current command value i _REF from the speed error amplifier 1 needs to be determined).

FIG. 5 is a block diagram showing details of the generation of signal _t1 during forward rotation. 51 is an absolute value circuit, 52 is a square root circuit, 53 is a multiplier with a coefficient k that multiplies the output √ _REF of the square root circuit 52 and the voltage (E ₂ +e _M ) detected from the anode of the thyristor Th _F ;
4 is a comparator, and 55 is a sawtooth wave synchronized with the timing carrier period T, which is selected so that if its peak value is e _T , k/e _T 2√ ³ ₂ is obtained. Immediately before the thyristors Th _F and Th _R fire, no current flows through the motor M, so the motor voltage
EM becomes only the induced voltage e _M , and the voltage on the anode side of _{the thyristor Th F becomes} (E ₂ +e _M ). transformer 2
The next voltage E ₂ can usually be regarded as a constant.

6 in FIG. 4 is a commutation failure prevention circuit, the details of which are shown in FIG.

IA _F and IA _R are integrators, Com _F and Com _R are comparators.

The condition for successful commutation is t ₁ > T・e _M ′/
(E ₂ +e _M ′). From this (E ₂ +e _M ′)t ₁ /T
>e _M ′ holds true. When the motor current is zero, the voltage applied to the thyristor is E ₂ + e _M ′ (during braking), E ₂ −
e _M ′ (during power running). Therefore, the integrator IA _F or _IAR creates (E ₂ +e _M ′)t ₁ /T, and the comparator detects that this has become larger than the induced voltage e _M ′.
If detected by Com _F or Com _R , time _{t 1} can be determined, so the thyristor Th _F or
By prohibiting the Th _R gate trigger, commutation failure can be prevented. As can be seen from the equation, during power running, t ₁ <0, so there is no problem.

Then in Figure 4, 7 and 8 are thyristors
Th _R Th _F drive circuits, 10 to 13 are AND (logical product) circuits, and 14 are inverter (not) circuits.

In the timing chart of Fig. 7, 701
represents timing generation, and 702 and 703 represent the primary and secondary voltages of transformer TF. 704 is the gate pulse of thyristor Th _F , 705 is the motor current, 706 is the speed deviation output, 707 is the motor voltage E _M (solid line) and motor induced voltage e _M (dotted line), 708
is thyristor Th _R commutation failure prevention pulse, 709 is thyristor Th _R gate pulse, 710 is transformer
711 is the primary current of TF, which is the transistor T _rP , T _rN
712 is due to the diodes D _P and D _N , and the exciting current of the transformer TF is ignored.

As can be seen from this time chart, control from driving (powering) to braking is performed smoothly.

Up to now, the configuration as a servo amplifier for a DC servo motor has been shown and only this has been explained, but the present invention applies an AC motor to the motor M,
It is also used as a cycloconverter for one phase.

FIG. 8 is a block diagram of another embodiment of the invention.

It is a system that controls a two-phase brushless motor M ₂ , and two circuits (A phase, B phase) shown in FIG. 4 may be used.

FIG. 9 is a schematic diagram of still another embodiment of the present invention.

91 to 9 in the circuit that drives the three-phase AC motor _M3
6 is a thyristor.

FIG. 10 is a block diagram of a fourth embodiment of the present invention. This is a combination of the primary side switch circuits shown in FIG. 8 into one.

Thus, in the present invention, since the motor current is intermittent, the motor induced voltage can be easily detected, speed and current detectors can be omitted, a DC tachogenerator is not required, and there is no delay in current control. It is small, does not require current detection feedback, is easy to control, and has high control performance. Moreover, the main circuit has a simple configuration and does not require a commercial power frequency transformer or rectification/smoothing on the secondary side.
Can be made lightweight and low cost.

That is, in the present invention, control of the primary side and secondary side of the transformer is performed in synchronous coordination, so that controllability with high power factor and efficiency can be achieved.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of the present invention, Fig. 2 is a motor current waveform diagram when the motor is running, Fig. 3 is a motor current waveform diagram when the motor is braking, and Fig. 4 is a block diagram of an embodiment of the present invention. , Figures 5 and 6 are some detailed views, Figure 7 is a time chart showing the operation of each part,
FIGS. 8, 9, and 10 are schematic diagrams of other embodiments of the present invention. 1... Speed error amplifier, 2... Timing generation circuit, 3... Transistor T _rN drive circuit, 4...
Transistor T _rF drive circuit, 5... Firing angle control circuit, 6... Commutation failure prevention circuit, 7... Thyristor
Th _R gate drive circuit, 8... Thyristor Th _F gate drive circuit, 9... Speed command voltage, 10 to 13...
...AND (logical product) circuit, 14...Inverter (not) circuit, 91-96...Thyristor, S...
... Commercial power supply, DS ... Rectifier diode, C ... Smoothing capacitor, D _P , D _N ... Feedback diode, TF
...Transformer, L...Reactor, M...DC motor, M ₂ =...2-phase brushless motor, M ₃ =...3
Phase AC motor.

Claims (1)

[Scope of Claims] 1. A switch circuit connected to the primary winding of the transformer to intermittent electromagnetic energy supplied from the DC power supply; a diode connected to provide feedback; and an electric motor connected to the secondary winding of the transformer via a thyristor, the switch circuit is opened and closed at a constant period T, and the thyristor is fired at a time t. ₁ is 0 < t ₁ < T/2 when the motor is running, and T・e' _M / (E ₂ + e' _M ) < t ₁ < T/2 when the motor is braking, where e' _M is the motor's A motor drive system characterized in that the induced voltage during control, _E2 , is the secondary voltage of the transformer.