JPS583591A - Controlling method for induction motor - Google Patents

Abstract

PURPOSE:To enable precise torque control by inputting four types of detection signals representing the operating states of a motor to a computer and generating a signal of torque data stored in advance in a memory by a retrieval signal. CONSTITUTION:When an induction motor 2 is operared by a VVVF inverter 1, four types of detection signals such as a current I1 from a detector 4, frequencies fi from detectors 4, 5, a voltage VM, a frequency from a speed detector 3 and a slip S obtained from the frequency fi are applied to the address retrieving unit 8a of a computer 8. The analyzed torque is stored in advance in a memory 8b, which is retrieved to obtain torque data obtained from the input, thereby generating the torque signal. Accordingly, analyzing function is not provided in the component, thereby simplifying it, and the error due to the temperature change of a secondary resistor can be remove, thereby controlling precisely the torque.

Description

[Detailed description of the invention] This invention is a variable voltage/variable frequency inverter (hereinafter referred to as vvv
The present invention relates to a method of controlling an induction motor using an inverter (referred to as a y-inverter), and particularly to a control method that enables precise torque control.

P! In recent years, advances in semiconductor technology have been remarkable, and it has become easier to realize power supplies with variable voltages and variable frequencies. The output torque of an induction motor (hereinafter simply referred to as an electric motor) changes over time due to changes in the resistance value of its secondary circuit due to temperature changes, so it is unsuitable for specialization in fields that require high-precision torque control. This will be explained with reference to Fig. 1. Fig. 1 (a) is an equivalent circuit for one phase of a motor, and Fig. 1 (b) shows this in a simplified manner. It is '1#
rl is the primary resistance, secondary resistance, Ll, L are -order leakage inductance, secondary leakage inductance, M is mutual inductance, and 8 is slippage. Here, ζvM is the primary voltage supplied by the inverter of the motor power supply. Yes, that v
In other words, rl e J * Ll e L 1M in the diagram is a constant determined by the motor, and the state quantity indicating the operating state of the motor is primary voltage VM e - next station wave number. f↓, sliding S,
- Next current 11. Excitation electricity 61! There is a next current P3 I2 at I@.

Now, considering the case where the motor constant does not change depending on the operating state, among the state quantities described above, the mutually independent state quantities are the primary voltage vM, the -order frequency f↓, and the slip 8, which are the only three sharp zeros.In other words, Once the three state quantities ■Mefb+8 are determined, all other state quantities are uniquely determined, and the operating state of the motor can be known. For example, V...
The three state quantities of l fA 18 are determined to be 11 r I
The state quantity of O+ lff1 can also be known using the motor constants, and as a result, the output torque of the motor can be calculated from the well-known Steinmetz equation ring. For each case where the −order leakage inductance L1+
The explanation will be simplified and considered by omitting the −th order resistance t.

That is, in FIG. 1(b), the rlJ magnetic current IO and the secondary current II are expressed by equations (1) and (2).

Amount @ = 0M / 2 to f↓Mj ・
・・・・・・・・・(1) b = 'thi/ ((f*
/8) +2ffALsj ) --- (2) Also, the torque T of the electric motor is expressed as follows〇 JP-A-58-
3591 (2) where k is a proportionality constant.

T = k I(1h −...(
3) Here, the secondary resistance r8 is doubled when the operating temperature is wide (-10 to +200)'0 due to temperature changes, for example.
f also changes, and in this case, as can be seen from equation (2), it also depends on the value of Ll, but the secondary current 11 will change even if the three state quantities of VM e fLr 8 mentioned above are the same. It can be seen from equation (3) that the torque T also changes by a large amount when the torque T changes by about 2 times.

As described above, in order to accurately control the output torque of the electric motor over a wide temperature range, it is necessary to know the value of the secondary resistance. However, it is difficult to accurately measure the secondary resistance under the operating conditions of the motor, and it is usually difficult to accurately measure the secondary resistance while the motor is in operation. There were interlayers that caused problems when control was required.

The present invention has been made in consideration of the above-mentioned points, and includes a detector that detects at least four state quantities, and input information of the output of the detector, and stores torque data stored in advance from the storage unit. Search 5 This invention provides a method for realizing an induction motor control device equipped with a combination Hatake-Yu and capable of performing precise torque control from special signal generation. First, the technical idea of the present invention will be explained. In Fig. 1(b), the secondary resistance r is not a constant determined by the motor, but by considering r as a state quantity that changes depending on the operating state, in this case, the state quantity is VM
# fA * 8 eIl I Io # II #
It can be thought of as rl ◎The mutually independent ones among these state quantities are VM e fL *8#Z1, and once these four state quantities are determined, even if I3 changes due to temperature, the motor's output torque remains constant. will be calculated.

Note that these mutually independent state quantities can be easily detected from the outside and can be made into Me fA + a eII without including r□ in the state quantity I shown in #I1 (b) Jζ. is clear.

In addition, in order to obtain the torque by obtaining such a state quantity, if it were to have a function to analyze the circuit of No. 111I(b), such a control method would be complicated and expensive, so it would not be a good idea. However, the present invention does not have such an analysis function, but by providing a combination with stored data in order to know the torque value from the four state quantities. This is a device that has the function of retrieving and sending signals from a pre-stored storage device section.This is shown in the following table.In other words, the table shows the stored data corresponding to the storage address of the storage device section. This shows an example of the relationship between the four state quantities Ihf↓r VM The input information obtained from the four state P7 quantities (11), (fA) e
(VM) e If it is searched according to the address for each of (8), it will be possible to generate a signal of the torque value of the analyzer in the operating state at the time of such input information @The table number is also shown. Tn is the circuit 4 of FIG. 1(b), II e fA rVM, 8 is II,
Le ha i VM% e as (Torque detection value in D operation is shown.) An application example of the present invention realized based on the following technical idea-ζ is shown in FIG. 2 ζ.

In Fig. 2 4ζ, 1 is VVVP inverter, 2 is VVV
F Inverter 1 output is supplied to the electric motor, 3 is the electric motor 2
A speed detector that detects the rotational speed frequency fM of 4, 4 is the primary current! A current detector detects dust, 5.6 is the primary frequency f↓ of the VVVP inverter l output, a frequency detector and a voltage detector detect the -next voltage, and 7 is the primary frequency factor f↓ and the rotation speed frequency fM. A known slip detector that gives a slip 8 from the signal Kukata, 8 is a combination that is equipped with a location search section 8m and a storage device section 8b and generates a detection signal of torque T. The current detector 1 frequency detector 6. Each output of the output device 6 and the slip detector 7 is given to the address search section 8a, and from these input information, the analyzer torque values as shown in the table are stored in advance. The torque data obtained from the input information is retrieved from the storage unit 8b, and a detected torque signal T is sent out.

As described above, the device shown in FIG. 2 detects the detection signals of the four state variables hf↓ and vMI8 in motor control using the vvvP' inverter. It is a system that obtains input information at the same time, searches for torque data corresponding to this detected state quantity, and outputs it externally, without having any analysis function in the control device. This makes it possible to exceptionally detect output torque in any operating state. Furthermore, it is clear that this eliminates detection errors caused by temperature changes due to secondary resistance and enables highly accurate torque control. Note that it is assumed that the analyzer torque values corresponding to the four state quantities are stored. As described above, if the address search unit 81 has an interpolation function for creating torque data from between the stored torque data, the address search unit 8a searches the storage address of the storage device unit 8b, and 9. The torque data of the address is retrieved, or the address search unit 8m further creates unstored torque data from those torque data to generate a valid detected torque signal. According to the present invention, it is possible to provide a method for realizing a motor control device using a VVVF inverter that is capable of precise torque control without having an analysis function in its constituent parts.
II * fA a v,, e 8 as state quantities
However, it is clear that the present invention can be applied to the same effect even if other state quantities such as fM, effective (reactive) current value, etc. are used as part of these four parts. Furthermore, it goes without saying that the effect can be further enhanced depending on the case by setting the number of state quantities to six or more instead of limiting it to four.

[Brief explanation of the drawing]

Fig. 1 is an equivalent circuit diagram for one phase of the electric motor, and Fig. 2 is a control system diagram showing an embodiment according to the present invention.
Variable voltage/variable frequency inverter (VVVF inverter), 2...Induction motor (motor), 3...
・IO Speed detector, 4...Current detector, 5...Frequency detector, 6...Voltage detector, 7...Slip detector, 8... ···Computer. Patent applicant Toyo Denki Seizo Co., Ltd. Representative Atsushi Doi

Claims (1)

[Scope of Claims] 1. In an induction motor control method for controlling the output torque of an electric motor using a variable voltage/variable intermittent inverter, at least four types of mutually independent state quantities indicating the operating state of the electric motor are provided. A method for controlling an induction motor, characterized in that, in addition to obtaining detection signals, a signal of torque data stored in advance in a storage unit is generated from search information based on the detection signals. 2. The induction motor control method 0 according to claim 1, in which the detection signal of Class 411 is configured to use a primary current, a primary frequency, a primary voltage, and a slip.