JP2600280B2 - Method for estimating rotor temperature of induction motor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for estimating a rotor temperature required when calculating a slip frequency in a vector control device for calculating a slip frequency of an induction motor.

[Conventional technology]

As a vector control method for an induction motor, a slip frequency control type vector control is the most common. In the slip frequency control method, the slip frequency ω _S of the induction motor is calculated and controlled based on the circuit constant of the induction motor as shown in equation (1), and a torque characteristic equivalent to that of a DC motor can be obtained.

ω _S = (R ₂ × I _t ) / Φ ₂ (1) where, ω _S : slip frequency R ₂ : secondary resistance value of the induction motor Φ ₂ : secondary flux linkage of the induction motor I _t : torque Component current However, the secondary resistance value of the induction motor greatly changes depending on the temperature of the rotor.
% Variation. As a result, the generated torque of the electric motor fluctuates to the same extent, and good torque characteristics cannot be obtained.

Conventionally, as shown in FIG. 3, a temperature difference compensation value Δθ between a stator winding temperature and a rotor temperature calculated using a current command value corresponding to a secondary current, and a detected value θ ₁ of the stator winding temperature. The rotor temperature θ ₂ is estimated from the sum of the above and the actual value of the secondary resistance value is predicted based on a relationship such as, for example, equations (2) and (3) (Japanese Patent Laid-Open No. 58-215992, See JP-A-60-131088).

θ ₂ = θ ₁ + Δθ (2) R ₂ = R ₂₀ ｛1 + K ₀ (θ ₂ −θ ₀ )｝ (3) where θ ₂ : rotor temperature estimated value θ ₁ : stator winding temperature detected value Δθ : Compensation value of temperature difference between stator winding and rotor R ₂ : Estimated value of secondary resistance R ₂₀ : Secondary resistance value at reference temperature θ ₀ K ₀ : Temperature coefficient of resistance of secondary conductor θ ₀ : Rotor at slip frequency calculation In FIG. 3, 1 is a three-phase AC power supply, 2 is a current control type inverter, 3 is an induction motor, 4 is a speed detector,
5 is a temperature detector, 6 is a current amplifier, 7 is a primary current calculation unit, 8 is a speed control unit, 9 is a magnetic flux-current converter, 10 is a coefficient unit, 11 is a divider, 12, 13 are coefficient units, 14 is a multiplier, 100
Denotes a rotor temperature estimating unit.

In the configuration of the control device as described above, the temperature difference compensating circuit 16 between the stator winding and the rotor is usually constituted by a primary delay element circuit or a combination of a plurality of primary delay circuits.

The temperature difference compensating circuit 16 is generally realized by an analog circuit or software processing by a microcomputer. When a control current is input, the temperature difference compensating circuit 16 detects the stator winding temperature and the rotor temperature simultaneously with detecting the stator winding temperature. Is simulated, and the rotor temperature is estimated as described above.

[Problems to be solved by the invention]

In the configuration of the control method as described above, once the control power supply is lost, the operation values of the compensation circuit are all cleared to zero, and the simulation value of the temperature difference between the stator winding and the rotor held as the operation value of the compensation circuit is also reduced. Becomes zero.

Therefore, when the power is turned on again, the calculation of the temperature difference starts from 0, and there is a problem that the simulation value between the actual stator winding and the temperature difference between the rotor and the rotor is different, resulting in a rotor temperature estimation error. The hatched portion in FIG. 4 corresponds to the temperature estimation error. The above situation is most remarkable when restarting after a power failure or when starting with a high temperature of the motor, and the generated torque of the motor greatly differs from the required torque, and the predetermined performance cannot be obtained. There was a problem.

The present invention has been made in view of such circumstances, and at the time of restarting after a power failure, etc., by performing control in consideration of the difference between the stator winding temperature and the rotor temperature,
An object is to realize vector control with high torque control accuracy.

[Means for solving the problem]

In order to achieve this object, a rotor temperature estimating method for an induction motor according to the present invention includes a temperature difference compensating unit for estimating a rotor temperature from a detected value of a stator winding temperature of a vector-controlled induction motor and a rotor loss. In the rotor temperature estimating method of the induction motor vector control device, when power is turned on, an increase in the rotor temperature with respect to the stator winding temperature is estimated based on a detected value of the stator winding temperature and a set value of the ambient temperature. It is characterized in that the estimated value is set as an initial value of the rotor temperature rise of the temperature difference compensating means.

[Action]

In the present invention, the amount corresponding to the temperature difference of the stator winding and the rotor when the power is turned on (4), (5) setting theta _a detected value theta ₁ and the ambient temperature of the stator winding temperature as Stator winding temperature rise value obtained from the difference (θ ₁ −θ _a )
, And this value is set as the initial value of the operation of the temperature difference compensation circuit.

_{Δθ (i) = K i (} θ 1 -θ a) ... (4) where, K _i denotes the initial value is expressed by the following equation.

Where Δθ _max : temperature difference between stator winding and rotor when motor is thermally saturated θ _1max : stator winding temperature when motor is thermally saturated θ ₁ : stator winding temperature when power is turned on Detection value θ _a : Ambient temperature reference setting value In this way, by setting the initial value of the temperature difference compensation circuit according to the temperature difference between the rotor and stator windings when power is turned on, not only during normal operation, Even in transient situations such as when restarting after a power failure or when starting with a high motor temperature, the temperature compensation of the secondary resistance value is accurately performed, so that the torque control accuracy is independent of the rotor temperature. High vector control can be realized.

〔Example〕

Hereinafter, the present invention will be specifically described based on embodiments shown in the drawings.

FIG. 1 shows a block diagram of a rotor temperature estimating unit 100 'for realizing the rotor temperature estimating method of the present invention.

In FIG. ₁ , the output Δθ of the temperature difference compensating circuit 16 between the rotor and the stator winding is added to the stator winding temperature detection value θ1, and the secondary resistance temperature is corrected according to the equation (4) as the rotor temperature estimation value. It has a configuration. And sets an initial value of the temperature difference compensation circuit 16 in accordance with the temperature difference between the stator winding temperature detection value theta ₁ and on the basis of the reference set value theta _a ambient temperature at power stator winding and the rotor.

In the figure, the constant of the coefficient unit 17 is given by equation (5), and is obtained in advance from the design value of the induction motor or the measured value on the actual machine. The switch 18 is used to set an amount corresponding to the temperature difference between the stator winding and the rotor when the power is turned on, in the temperature difference compensation circuit 16 as an initial value. Only when the control power supply is turned on, the amount corresponding to the temperature difference between the rotor and the stator winding is set as the initial value of the temperature difference compensation circuit 16 according to the equation (4).

FIG. 2 is a diagram showing a change in rotor temperature and a change in temperature compensation value according to the present invention. When the motor stops due to a power failure or the like, the temperature difference compensation value Δθ is cleared to 0, but when restarting, Δθ (i) is set as the initial value of the temperature compensation value.

〔The invention's effect〕

As described above, in the present invention, a compensation value corresponding to the temperature difference between the rotor and the stator winding is set in the temperature difference compensation circuit when the power is turned on. As a result, even when restarting after a power failure or when starting with a high motor temperature, the simulation of the temperature difference is started immediately after the start of operation from the level corresponding to the temperature difference at that time, so that normal operation is performed. In addition, it is possible to realize a control device for an induction motor in which the temperature difference between the rotor and the stator winding is accurately compensated even in the transient state as described above, and the vector control with high torque control accuracy is achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a rotor temperature estimating unit according to the present invention;
FIG. 2 is a graph showing the effect of the present invention, FIG. 3 is a block diagram of a conventional vector control device, and FIG. 4 is a graph showing a rotor temperature compensation operation showing a conventional problem. 1 ... three-phase AC power supply, 2 ... current control type inverter, 3
...... Induction motor, 4 ... Speed detector, 5 ... Temperature detector, 6 ... Current amplifier, 7 ... Primary current calculation unit, 8 ... Speed controller, 9 ... Flux-current converter, 10 ·································································································································································································· rotor, Temperature estimator

Continuation of the front page (72) Inventor Eiji Watanabe 2-3-1-1, Nishinomiya-shi, Yukuhashi-shi, Fukuoka Prefecture Inside Yasukawa Electric Mfg. Co., Ltd. (56) References JP-A-58-215992 (JP, A) JP-A-60-131088 (JP, A)

Claims (1)

(57) [Claims] 1. A method for estimating a rotor temperature of an induction motor vector control apparatus comprising a temperature difference compensating means for estimating a rotor temperature from a detected value of a stator winding temperature of a vector-controlled induction motor and a rotor loss. At the time of injection, an increase in the rotor temperature with respect to the stator winding temperature is estimated based on the detected value of the stator winding temperature and the set value of the ambient temperature, and the estimated value is used as the increase in the rotor temperature of the temperature difference compensating means. A rotor temperature estimation method for an induction motor, wherein the method is set as an initial value.