JPS6082082A - Secondary chopper controller of wound-rotor induction motor - Google Patents

Abstract

PURPOSE:To enable to perform stable high speed operation by lowering the secondary frequency at the high speed time, thereby preventing the chopper current from decreasing irrespective of the decrease in the slip at the high speed time. CONSTITUTION:A motor speed (n) is detected by a speed detector 7, compared and calculated with a set speed n* by a speed controller 9, a current reference I1* is outputted, compared and calculated with the primary current I1 of a motor detected through a current transformer 6 and a current controller 11, and the output controls the ON/OFF ratio of a chopper 4 through a phase controller 12. A frequency controller 15 inputs a speed signal (n) from a speed detector 7, and the pulse frequency of the pulse generator 13 is stepwisely lowered in response to the rise of the n. Thus, the chopper frequency (f) at the high speed time is lowered to flow the sufficient secondary current I2 even at the high speed time, thereby obtaining stable high speed operation.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides secondary chopper control of a winding type conductive electric maple, which controls the motor speed by connecting a secondary resistor and a chopper circuit in parallel to a secondary circuit. It is related to the device.

Technical background of the invention and its problems] An example of a conventional secondary chopper control device is shown in FIG.

In FIG. 1, a secondary resistor 2 is connected to the secondary side of a wound type conductive motor 1, and a chopper device consisting of a rectifier 3 and a chopper 4 is connected in parallel with this. By controlling the on-off ratio, the chopper current Ic is controlled, and this is superimposed on the secondary resistor current IR to control the secondary current, thereby making it possible to control the speed of the motor.

That is, the motor speed n is detected by the speed detector 7, and the set speed n*, ! 1. The speed control circuit 9 performs a comparison calculation and outputs a current reference current, and the current control circuit 11 performs a comparison calculation with the sleep current 11 detected via the current transformer 6, and the output is used for phase control. The on/off ratio of the chopper 4 is controlled via the circuit 12.

Note that 5 is a primary side breaker of the visiting electric motor l, and 13 is a pulse generator that supplies the frequency f of the chopper 4.

Figure 3 shows chopper flow I corresponding to chopper on-off.
An example of the relationship between the secondary resistor current I and the secondary current is shown in c.

As shown in Fig. 3, if the chopper period is △to and the on time is △1o, then the current increase when the chopper is on is △■
o can be approximated by the following formula.

dI.

△mu = Δt0xπ V = △to
Moon = p stone, S,, at. -cos (.1, .

Here, v, secondary voltage EV) V, R: Secondary rated voltage effective value EV] ω: Secondary voltage angular velocity [rad) L: Leakage inductance seen from the secondary terminal [H] S: Slip (PU ) t: Time [5ec] θ: Constant [rad] △to: Chopper on time [sec) In other words, when chopper on time Δt0 is controlled, motor secondary current I changes as Δt0 changes, and as a result, the motor The speed n of can be controlled.

However, the above Δt0 is a smaller value than the chopper period Δ1o, and at its maximum, Δ■o also reaches its maximum.

On the other hand, the chopper frequency is preferably about 300 to 1000 Hz because the speed control range is usually around 40 cm.
This is not desirable for electric R operation.

Also, in the high speed region, the slip S is small, so a.

There is a problem that the secondary current flow becomes small and the secondary current 2 does not flow sufficiently.

[Purpose of the invention]

The present invention provides a secondary chopper control device for a wound induction motor that can lower the frequency of the secondary chopper in the high speed region of the motor, thereby increasing the secondary current value at high speed and stably increasing the maximum speed. is intended to provide.

[Summary of the invention]

The present invention provides a secondary winding induction motor in which a secondary resistor and a chopper circuit are connected in parallel to the secondary side of the winding induction motor, and the on/off ratio of the chopper circuit is controlled to control the secondary current of the motor. The chopper control device is equipped with a frequency control circuit that sequentially reduces the chopper frequency of the chopper circuit when the speed of the motor increases above a predetermined value. This allows for stable improvement of performance.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

FIG. 2 is the same as FIG. 1 except that a frequency control circuit 15 for controlling the pulse frequency f of the pulse generator 13 according to the motor speed n is added to the conventional FIG. 1.

In the present invention, Δ1o is made thicker by the amount that slip S decreases in the high-speed region of the electric motor, and the chopper frequency if is lowered to prevent a decrease in ΔIo.

That is, the frequency control circuit 15 inputs the speed signal n from the speed detector 7, and lowers the pulse frequency of the pulse generator 13 in steps as n increases.

This allows sufficient secondary current to flow even at high speeds, resulting in stable high-speed operation.

FIG. 4 shows an example of the chopper current (i) and the secondary resistor current (i) when the chopper frequency is lowered.

〔Effect of the invention〕

As explained above, according to the present invention, in a secondary chopper control device in which a chopper circuit is connected in parallel with a secondary resistor on the secondary side of a wound induction motor, the frequency of the secondary chopper is This prevents a drop in the chopper current and allows a sufficient secondary current to flow, regardless of slippage at high speeds, which enables stable high-speed operation and reduces the maximum operating speed to the secondary short-circuit speed. It can be raised up to a nearby level.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing an example of a conventional secondary chopper control device, Fig. 2 is a system diagram showing an embodiment of the present invention, and Figs. 3 and 4 show cases in which the chopper frequency is high and low, respectively. 2 is a time chart showing current waveforms at various parts. 1 Wound induction motor 2 Secondary resistor 3 Rectifier 4 Chopper 7 Speed detector 9 Speed control circuit 11 Current control circuit 12 Phase control circuit 13 Pulse generation circuit 15 Frequency control circuit (8733) Patent attorney Akira Inomata ( Others 1
Name) @1 Figure 2 Figure 3 Figure 1? Figure 4 - 11111÷t

Claims (1)

[Claims] A secondary chopper control device for a wound type rust conduction motor that connects a secondary resistor and a chopper circuit in parallel to the secondary side of the wound type induction motor and controls the on/off ratio of the chopper circuit to control the secondary current of the motor. A secondary chopper control device for a wound induction motor, comprising a frequency control circuit that sequentially reduces the chopper frequency of the chopper circuit when the speed of the motor increases to a predetermined value or higher.