JPH0757117B2 - Permanent magnet synchronous motor drive circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a permanent magnet synchronous motor drive circuit suitable for rotation control of a permanent magnet synchronous underwater motor used for a propulsion motor of an unmanned submersible.

[Prior Art] An unmanned submersible of this type is intended to bring a television camera into the water, such as the bottom of a dam, which is difficult for humans to enter. An underwater motor for propelling this is generally used for power transmission. It is connected to the equipment on the ground side by a cable and operated by remote control from the ground. Therefore, most of the underwater running resistance during running of the submersible is due to this power transmission cable, and the smaller the diameter of the cable, the more advantageous.

For this reason, a permanent magnet DC machine that requires only two power transmission lines (minimum) is optimal as the underwater motor. In addition, this permanent magnet DC machine has a reversible rotation direction and a speed range. It has the advantages that it is large and the output torque is proportional to the input current.

When using a permanent magnet type DC machine as an underwater motor, it is necessary to use a liquid immersion type motor in order to withstand water pressure and be small and lightweight.In this case, the commutator has the following problems. occured.

(1) The commutator becomes dirty.

(2) A liquid film is generated between the brush and the commutator, resulting in poor contact.

(3) For the above reason, an arc is generated and a decomposed gas of the liquid is generated.

For this reason, the brush and commutator have a short life, and maintenance must be performed frequently.

Therefore, an attempt was made to solve the above-mentioned problems by using a DC brushless submersible motor as shown in FIG. In this figure, 1 is a permanent magnet synchronous motor consisting of armature windings U, V, W and a rotor 2, and each armature winding U, V, w has an exciting current IU, IV, IW are supplied,
A rotating magnetic field is formed so that the rotor 2 made of a permanent magnet rotates.

Here, the inverter 3 includes MOSFETs (Ti = 1, 2 ...
6) and a diode Dai are connected in anti-parallel, and a switching element Qi formed by connecting a diode Di in series is bridge-connected. At the input end of the inverter 3,
A full-wave rectifier DS composed of four diodes DS1 to DS4 is connected in parallel. Further, a DC current is supplied to the rectifier DS from a DC constant current source 5 on the ground side through a power cable 6, and the polarity of this DC current is determined by a polarity determiner 7.

On the other hand, the magnetic pole position of the rotor 2 is detected by the Hall sensor 8 and the detection output is supplied to the on / off determiner 9. The on / off determiner 9 determines the rotation direction of the rotor 2 based on the output of the polarity determiner 7, and switches the switching element Qi by 120 ° to pass the exciting currents IU, IV, IW necessary for this rotation. Energize sequentially. FIG. 7 shows the waveform of each part in this control. FIG. 7 (a) shows the waveform at the time of normal rotation, and FIG. 7 (b) shows the waveform at the time of reverse rotation. In addition, in FIG. 7, V
As shown in FIG. 6, U, VV, VW are the voltages between the power supply terminals of the armature windings U, V, W and the neutral point NP.

In such a configuration, the polarity of the DC constant current source 5 is positive /
When switched to the opposite, this is detected by the polarity determiner 7, the energization sequence of the switching element Qi is reversed, and the rotation direction of the motor 1 is reversed. Further, the speed of the motor 1 can be changed by increasing or decreasing the current.

[Problems to be Solved by the Invention] In the above-described conventional inverter circuit, the rectifier DS has to be provided because the current is turned on / off by the unidirectional switching elements Q1 to Q6. For this reason,
When the submersible motor continues forward or reverse rotation,
Although there is no problem at all, when switching from normal rotation to reverse rotation or reverse rotation to normal rotation, a short-circuit mode appears and elements Q1 to Q6 and
There was a drawback that DS1 to DS4 would be destroyed. For example, at time ta (Fig. 7) during normal rotation of the motor, if the polarity of the power source is reversed and a reverse rotation command is given, the switching elements Q1 and Q5 that were on until then are Q2 and Q4. Is switched to and Q1 and Q5 are turned off. In this case, the current from the DC constant current source 5 flows through DS2 → Q2 → V → U → Q4 → DS3 and returns to the DC constant current source 5. However, since the motor 1 maintains the normal rotation at the moment of switching, the generation state of the motor induced voltage is the same as the state of the normal rotation, and the induced voltage causes the armature winding U → switching element Q4 → rectifier DS → Q2.
→ The short circuit current of V flows by being superimposed on the above current (DC constant current source 5 has a high impedance, so it flows independently of the short circuit current), and the element corresponding to the short circuit current path (Q2 in the above example). , Q4, DS1 to DS4) could be destroyed.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a DC current source that supplies a variable current that can be switched between positive and negative directions to a permanent magnet synchronous motor, and a permanent magnet synchronous motor. It comprises a magnetic pole detector for detecting the magnetic pole position of the rotor, and an inverter which is composed of a plurality of switching elements and which drives the permanent magnet synchronous motor by energizing each switching element according to the magnetic pole position. In the permanent magnet synchronous motor drive circuit, the direct current source is directly connected to the input terminal of the inverter, each switching element constituting the inverter, the source and the source and the gate and the gate are connected, and each drain A bidirectional switching element is constructed by a pair of MOSFETs forming both ends of the switching element. Characterize.

[Operation] According to the above configuration, when the polarity of the DC current source is switched while the motor is rotating, the exciting current from the power source and the phase voltage of the motor are in opposite phases, the motor is braked, and the reverse power running operation is performed. Transition. At this time, the current due to the induced voltage generated to maintain the rotation of the motor before the switching is canceled by the reverse current supplied from the DC current source.

Further, the output torque of the motor is proportional to only the current supplied from the DC current source, regardless of the rotation direction or rotation speed.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In this figure, parts corresponding to the parts in FIG. 6 are assigned the same reference numerals and explanations thereof are omitted.

This embodiment is different from the conventional motor drive circuit shown in FIG. 6 in the following points.

(1) In the inverter 13 of this embodiment, a bidirectional switching element Q1i (i = 1, 2 ... 6) is used instead of the switching element Qi of the inverter 3 shown in FIG. The switching element Q1i has a pair of MOSFETs T1i whose sources are connected to each other and whose gates are connected to each other and whose drains are both ends of the switching element Q1i.
T2i and diode connected in anti-parallel to this MOSFET T1i
D1i and diode D2i connected in anti-parallel to MOSFET T2i
Composed of and.

(2) The rectifier DS is removed, and the output of the DC constant current source 5 is directly supplied to the input end of the inverter 13 via the power cable 6.

(3) Only the output of the hall sensor 8 is supplied to the on / off determiner 14, and the polarity determiner 7 of FIG. 6 is removed.

In such a configuration, if a positive DC current Idc at the input end of the inverter 13 is supplied and the switching elements Q11 to Q16 are sequentially energized as shown in FIG. 2, a rotating magnetic field is generated by the exciting currents IU to IW, The motor 1 rotates normally. in this case,
The rotation speed and torque of the motor 1 are determined by the current Idc.

Next, when the polarity of the current Idc is reversed, the relationship between the exciting currents IU to IW and the phase voltages VU to VW becomes an antiphase relationship as shown in Fig. 3, and the armature windings U, V, W are generated. The induced voltage is regenerated to the DC constant current source 5 side and the motor 1 is braked. In this case, the induced voltage tries to maintain the current before the polarity reversal, but is canceled by the constant current Idc from the DC constant current source 5, and does not form a short circuit current as in the conventional case. Thus, the motor 1 is braked, and then the motor 1 shifts to the reverse power running operation shown in FIG. At this time, since the output order from the Hall sensor 8 is also reversed, the firing order of the switching element Q1i is also reversed, and the reversing power running operation is performed while the exciting currents IU to IW and the phase voltages VU to VW maintain the same phase.

When the polarity of the current Idc is reversed again to return to the initial state, as shown in FIG. 5, the exciting currents IU to IW and the phase voltage VU
The phase is opposite to VW and the motor 1 is braked, and the normal rotation power running operation shown in FIG. 2 is immediately started. Also in this case,
The induced voltage generated in the armature windings U, V, W is canceled as described above, and the short circuit current is not formed.

In each operation described above, switching elements Q11 to Q16
Functions as a bidirectional switch, and simultaneously causes the current due to the induced voltage generated when the polarity of the current Idc is switched and the current Idc from the direct current constant current source 5 to disappear so that the current due to the induced voltage disappears.

Thus, in this embodiment, since the input side of the inverter 13 does not have a rectifier and the switching elements Q11 to Q16 of the inverter 13 are bidirectional, both current and voltage are positive and negative on the input side of the inverter 13. Can take the value of.
As a result, ON / OFF of each of the switching elements Q11 to Q16 is determined only by the rotation angle of the rotor 2 regardless of whether the torque is positive or negative, and the magnitude of the torque is proportional to the input DC current Idc. That is, if the permanent magnet synchronous motor drive circuit according to the present embodiment is used, as in a conventional permanent magnet type DC machine having a brush and a commutator, it outputs a tokule proportional to the bidirectional DC input current, and complete 4 It becomes possible to perform quadrant operation.

[Effects of the Invention] As described above, according to the present invention, the following effects can be achieved.

(A) When the polarity of the DC current source is switched while the motor is rotating, the exciting current from the power source and the phase voltage of the motor are in opposite phases, the motor is braked, and the reversing power running operation is started.

(B) At the time of switching the power source polarity, the current due to the induced voltage generated to maintain the rotation of the motor before the switching is canceled by the reverse current supplied from the DC current source. This eliminates the inconvenience that a short circuit current flows through each switching element and protects each switching element.

(C) Since the output torque of the motor is proportional to only the current supplied from the DC current source regardless of the rotation direction and the rotation speed, torque control can be performed by controlling the current. As a result, full four quadrant operation can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention, FIGS. 2 to 5 are waveform diagrams for explaining the operation of the embodiment, and FIG. 6 is a conventional permanent magnet synchronous motor drive. FIG. 7 is a block diagram showing the configuration of the circuit, and FIG. 7 is a waveform diagram for explaining the operation of the circuit. 1 ... motor, 2 ... rotor, 3,13 ... inverter, 5
...... DC constant current source, D1i, D2i (i = 1,2 ・ 6) …… Diode, DS …… Rectifier, Q1i …… Switching element, T1
i, T2i …… MOSFET.

Claims (1)

[Claims] 1. A direct current source for supplying a variable current which can be switched between positive and negative directions to a permanent magnet synchronous motor, a magnetic pole detector for detecting a magnetic pole position of a rotor of the permanent magnet synchronous motor, and a plurality of switching elements. A permanent magnet synchronous motor drive circuit comprising an inverter for driving the permanent magnet synchronous motor by energizing each switching element according to the magnetic pole position, wherein the DC current source is input to the verter. Each switching element that is directly connected to the end and that constitutes the inverter is configured by a pair of MOSFETs in which a source and a source and a gate and a gate are connected and each drain is at both ends of the switching element. A permanent magnet synchronous motor drive circuit characterized by using a directional switching element.