JPH048185A - Emergency stop circuit for synchronous motor - Google Patents

Abstract

PURPOSE:To shorten the brake distance at the time of emergency stop by detecting the rotational speed of a synchronous motor and making the short circuit resistance between feeder lines for the synchronous motor variable according to thus detected rotational speed. CONSTITUTION:AC voltages R, S, T are fed to an inverter circuit 1 for driving a synchronous motor M1. A variable short circuit resistance circuit 2 is connected between feeder lines for the synchronous motor M1 and short-circuits the feeder lines through a resistor at the time of emergency stop. A rotational speed detecting circuit 3 is connected between the feeder lines for the synchronous motor M1 in order to detect the rotational speed of the synchronous motor M1 and to output a rotational speed signal Vomega which is then fed to the variable short circuit resistance circuit 2 in order to vary the short circuit resistance in the variable short circuit resistance circuit 2 according to the rotational speed signal Vomega.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an emergency stop circuit for a synchronous motor, and more particularly to an emergency stop circuit for a synchronous motor using a permanent magnet.

Conventionally, an emergency stop circuit for a synchronous motor of this type short-circuits the power supply lines of the synchronous motor M with a fixed resistor during an emergency stop of the synchronous motor, as shown in FIG. It was supposed to stop the electric motor.

Problems to be Solved by the Invention The conventional emergency stop circuit for a synchronous motor described above is a circuit that short-circuits the power supply lines of the synchronous motor with a fixed resistor, so when the rotational speed of the synchronous motor changes, the synchronous motor stops. The disadvantage is that the deceleration torque of the synchronous motor decreases due to the armature inductance, and the control distance until an emergency stop becomes longer.

The present invention has been made in order to eliminate the above-mentioned drawbacks inherent in the conventional technology, and therefore, an object of the present invention is to provide a novel emergency stop for a synchronous motor that makes it possible to shorten the braking distance during an emergency stop. The purpose is to provide circuits.

Means for Solving the Problems In order to achieve the above object, an emergency stop circuit for a synchronous motor according to the present invention includes means for detecting the rotational speed of the synchronous motor, and a means for detecting the rotational speed of the synchronous motor detected by the detection means. and means for varying the short circuit resistance between the power supply lines of the synchronous motor according to the power supply line of the synchronous motor.

EXAMPLE Next, a preferred embodiment of the present invention will be specifically explained with reference to the drawings.

FIG. 1 is a block diagram showing an example of the present invention.

Referring to FIG. 1, AC voltages R, S, and T are input to an inverter circuit 1, and the output of the inverter circuit 1 drives a synchronous motor M1. The short-circuit resistance variable circuit 2 is connected between the power supply lines of the synchronous motor M1, and the rotation speed detection circuit 3 is configured to short-circuit the power supply lines of the synchronous motor and the machine M1 with a resistance during an emergency stop. It is connected between the power supply lines of the synchronous motor M1, detects the rotation speed of the synchronous motor M1, and outputs a rotation speed signal Vω. Rotation speed signal Vω
is input to the short-circuit resistance variable circuit 2, and the short-circuit resistance in the short-circuit resistance variable circuit 2 is varied according to the rotational speed signal Vω.

FIG. 2 is a detailed circuit diagram of the short-circuit resistance variable circuit 2.

Next, the operation of the circuit shown in the second section will be explained. The rotational speed signal -.omega. is input to comparators OPI and OP2. Comparator OP2 determines that rotational speed signal Vω is equal to reference voltage ν&1
When it becomes 2 or less, close the switches 5lli4 to SW6,
The comparator OPI closes the switches SWI to S%l13 when the rotational speed signal Vω becomes equal to or less than the reference voltage Vω1. Here, if the magnitude relationship between the reference voltages Vω1, vω2 and the rotational speed signal νω is determined as Vω1<v&<vω2, then the short-circuit resistance of each phase of the synchronous motor is such that the rotational speed signal V& is ! When ≦Vω, R1
+R4, R2+R5, R3〒R6te, Vta (V
*1 (7) In some cases, they become R,, R2, and R3, respectively. In this way, the short circuit resistance between the power supply lines of the synchronous motor M1 can be varied according to the rotational speed of the synchronous motor M1.

In this embodiment, the circuit configuration is such that the short circuit resistance is varied in two stages, but it is clear that multistage switching can be realized by adding resistors, switches, and comparators.

FIG. 3 is a detailed circuit diagram of the rotational speed detection circuit 3.

Next, the operation of the circuit shown in FIG. 3 will be explained. Back electromotive force U1 of synchronous motor Ml. V1. W is full-wave rectified by diodes D1 to D6 and input to the insulated amplifier circuit 3a, thereby obtaining a rotation speed signal Vω that is insulated from the power system potential of the synchronous motor 141.

Next, it will be explained that according to the present invention, the braking distance during an emergency stop of the synchronous motor M1 is reduced.

FIG. 4 is an equivalent circuit diagram of one equivalent of the synchronous motor Ml when the synchronous motor Ml is short-circuited by a resistor Ra.

Referring to FIG. 4, the deceleration torque T of the synchronous motor Ml is given by equation (1).

Here, T: Deceleration torque R: Circuit resistance (R=Ra+Rm, Ra: Short circuit resistance, R1
, synchronous motor internal resistance) ψ・Back electromotive force constant ω of the synchronous motor: Electrical angular frequency (&l=P・ω, P・The number of magnetic pole logarithms of the synchronous motor, Int; Mechanical angular frequency) P・The number of magnetic pole logarithms of the synchronous motor Lm: Internal inductance of synchronous motor? In order to find the conditions for maximizing the gi speed torque, by differentiating equation (1) with respect to ω and setting d7/d*=O, equation (2) is obtained.

ω. ”-(2) L.

FIG. 5 shows a graph of Equations (1> and (2)). Equation (3) is obtained by transforming Equation (2).

R = L, , ωo (3) By changing the short-circuit resistance Ra according to the rotation speed of the synchronous motor so as to satisfy equation (3), the deceleration torque can always be maximized, and the braking during an emergency stop can be The distance can be reduced.

As described in detail, the present invention has the effect of reducing the braking distance during an emergency stop by varying the short circuit resistance between the power supply lines of the synchronous motor according to the rotational speed of the synchronous motor. 3 obtained

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the present invention, and FIG.
The figure shows a detailed circuit example of the short-circuiting variable resistance circuit of Fig. 1, Fig. 3 shows a detailed circuit example of the rotational speed detection circuit of Fig. 1, and Fig. 4 shows a synchronous motor short-circuited with a resistor. Fig. 5 is a graph showing the electrical angular frequency and deceleration torque of the synchronous motor derived from the equivalent circuit of Fig. 4, and Fig. 6 is a circuit diagram showing a conventional example. be. R, S, T...AC voltage, 1...Inverter circuit,
Old...Synchronous motor, 2...Short-circuit resistance variable circuit, 3.
・Rotation speed detection circuit

Claims (1)

[Claims] In an emergency stop circuit for a synchronous motor, which is connected between the power supply lines of the synchronous motor and is equipped with a short-circuit resistor that stops the synchronous motor in an emergency stop, a means for detecting the rotational speed of the synchronous motor; and means for varying short-circuit resistance between power supply lines of the synchronous motor according to the rotational speed of the synchronous motor.