JPH01311885A - Slip measuring device for induction motor - Google Patents

Abstract

PURPOSE:To easily and effectively monitor the malfunction of a load unit coupled to an induction motor by multiplying a power source frequency by using a multiplier, and counting the multiplied pulse output of the multiplier output during a period of the number determined by the pulse output of a rotating pulse generator to measure the slipping amount of the motor. CONSTITUTION:When an induction motor 1 is rotated, a pulse is output from an encoder 4 at each predetermined angle rotation of its rotary shaft 3. The pulse from the encoder 4 is divided in frequency by the frequency dividing rate determined on the basis of the rotating angle for measuring its torque, and fed to a controller 6. On the other hand, the 3-phase output of a power source 2 is multiplied by a multiplier 6, fed to a counter 6, and counted. A latch circuit 9 latches the counted value of the counter 6 during a period of the predetermined number of the pulses output from the encoder 4, and measures the slipping amount of the motor 1.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for measuring the amount of slip of an induction motor, which is useful information for diagnosing abnormalities in the induction motor or a load device connected thereto.

BACKGROUND OF THE INVENTION As a device of this kind, Japanese Patent Publication No. 56-2646 ``Induction Motor Load Detection Device'' is known.

This consists of a pulse generator that detects the rotation of the induction motor, a first counter that subtracts and counts clock pulses from a predetermined number of cycles of the power supply frequency, and a predetermined cycle of the pulse generator. It consists of a second counter that adds and counts clock pulses to a predetermined negative value, and an adder for both companies' numerical values.

In this case, if we let t be the sum of a predetermined number of cycles of the power supply frequency and the sum of a predetermined number of cycles of the T1 pulse generator, these lightnesses are equal to T in the synchronized state. An appropriate number of periods with which t coincides is selected, and the first
, fT-ft is selected as the initial value of the second counter, respectively, where f is the frequency of the clock pulse. As a result, when the power supply frequency changes and T changes by ΔT, and the rotation of the induction motor changes due to slip and t changes by Δ, the sum of the counts N and n of the first and second counters, X, is as follows. It will be as follows.

x = n + N = f (ΔE - ΔT) This gives the rotation change (time) due to motor slip, which is corrected for the rotation change due to the change in power supply frequency, and this rotation, which has been separately determined in advance, is obtained. The magnitude of torque (load) is determined from the relationship between change and torque.

Problems to be Solved by the Invention However, since the power supply frequency and the motor rotation period are determined separately and added, the circuit configuration inevitably becomes complicated.

In addition, the selection of the frequency of the pulse generator that detects rotation is
It is determined based on the cycle of the power supply frequency, for example 0.1 seconds (50Hz), and cannot be measured based on the actual rotation of the motor. Therefore, it is difficult to diagnose the failure of the motor or the equipment connected to it. There is a problem in that it is not possible to obtain the instantaneous slip or torque required for each revolution of the motor, or even for each even smaller rotation angle.

Method for Solving the Problems In order to solve the above problems, the present invention provides an apparatus in which slip is determined based on an appropriately selected rotation angle of an induction motor, and in which the circuit configuration is simplified. It includes a pulse generator for detecting the rotation of an induction motor, a power frequency multiplier, and a multiplied pulse output of the multiplier that is sent out during a predetermined number of cycles of the pulse output of the pulse generator. It consists of a counter for counting.

Furthermore, the temperature of the induction motor itself changes with changes in ambient temperature, load changes, and the like. Therefore, the second and third inventions are
This influence is automatically corrected, and in addition to the first invention, the invention further includes a temperature detector of the induction motor and a multiplied pulse output of a multiplier or a calculation unit based on the output of the temperature detector. A correction section that performs calculations is added.

In addition, the fourth invention is a difference in power supply frequency, that is, 50
This invention is designed to automatically correct the relationship between slip and torque that differs between Hz and 60 Hz, and in addition to the first invention, it further includes a power supply frequency measurement circuit and a multiplication method based on the measured frequency. A frequency correction section is added to correct the multiplied pulse output of the device or the arithmetic device.

In the first invention described above, the pulse generator sends out a pulse output every time the induction motor rotates by a certain angle, and the pulse output is divided by a predetermined number and then sent to the counter as a counting period signal. Added. On the other hand, the power supply frequency is multiplied by a multiplier according to the required measurement resolution and introduced into the counter as pulses to be counted,
The count is repeated at each counting cycle, and information corresponding to the counted value, that is, the slip of the motor, is obtained. Also,
Based on this, the corresponding torque is calculated by the calculator.

However, in this case, the standard for determining slip is the pulse output of the pulse generator that corresponds to the rotation angle of the induction motor, and by simply selecting how many pulses to count the multiplied pulse output, A slip is obtained for each rotation angle of the motor, and apparent changes in slip due to fluctuations in the power supply frequency are also offset.

Further, in the second and third inventions, the frequency of the multiplied pulse output is changed according to the output of the temperature detector, or the coefficients of the calculation formula of the yi and parts are changed, or the slip and torque are changed with respect to the temperature. Related data is switched.

Therefore, the true torque can be determined based on the relationship between slip and torque corresponding to the temperature at that time without being aware of the temperature.

Further, in the fourth invention, the power supply frequency is constantly measured and it is determined whether it is 50 Hz or 60 Hz, and the frequency of the multiplied pulse output is changed accordingly, or the frequency of the multiplied pulse output is The coefficients of the equation are changed, or the relationship data between slip and torque is changed. Therefore, the true torque at that time can be obtained without being aware of the power supply frequency.

Embodiment In FIG. 1, 1 is an induction motor, and its rotating shaft 3
An encoder 4 is coupled to the encoder 4, and its output is sent to a control section 6 via a frequency dividing section 5. 2 is a power source for the induction motor 1, and its three-phase output is sent to a counting unit 8 via a multiplier 7.
is being sent to. The count value of the counting section 8 is sent to the first latch circuit 9, and the latch value of the latch circuit 9 is
The data is read into the calculation unit 10 based on the command 0.

Then, the calculated value of the calculation unit 10 is calculated by the second latch circuit 11.
The value latched there is sent to the D-A converter 12.
The signal is converted into an analog output and sent to a display, transient recorder, FFT analyzer, etc. (not shown).

The control unit 6 determines the reset timing for the counting unit 8, first, ! @2 This is a part that sends each latch timing command to the latch circuit 9 11 and each command of calculation start timing to the calculation unit 10, and applies the first latch command to the first latch circuit 9 at predetermined intervals. , an output that is slightly delayed from the first latch command is applied to the counter 8 as a reset command and to the calculation unit 10 as a calculation start timing command, and then the second latch is reheated for a predetermined time that covers the calculation time of the calculation unit 10. A command is applied to the second latch circuit 11.

In the above, when the induction motor 1 rotates, a pulse is sent from the encoder 4 every time the rotation shaft 3 rotates by a predetermined angle, and the pulse is determined based on the rotation angle at which the torque is measured in advance in the frequency dividing section 5. The frequency is divided by the frequency division ratio,
It is sent to the control section 6. On the other hand, the three-phase output of the power supply section 2 is sent to the multiplier 7, which first converts the rising and falling edges into pulses, and
By adding the signals, the signals are multiplied by 6, and then multiplied according to the required measurement resolution and sent to the counting section 8 for counting.

Then, the counted value is latched in the first latch circuit 9 by the first latch command from the control section 6, and is reset after being latched.

Therefore, the first latch circuit 9 has a count value corresponding to the periodic rotation state and the rotation ratio of the rotation state at that time after sending out the multiplied pulse corresponding to the power frequency at every predetermined rotation angle of the induction motor 1. This is latched, and by monitoring this, the fluctuation state of the slip can be determined. Furthermore, this is sent to the calculation unit 10, where it is converted into torque based on the relational expression between slip and torque determined in advance, and is latched into the second latch circuit 11 every time the calculation is completed, and the D- The A conversion output is converted to an analog signal and sent to a display device, etc.

The above is a case where slip or the corresponding torque is measured under conditions of constant temperature, but in places where temperature changes are unavoidable, even if the slip is the same as shown in Figure 3, As the torque changes when the temperature changes, the true torque cannot be determined.

In the second embodiment, this correction is automatically performed. That is, as shown in FIG. 2, the induction motor 1 is provided with a temperature detector 21, and its output is converted into a digital value via the A-D converter 22, which is then input to the multiplier 7 in FIG. Ratio multiplier 2 intervenes in opening of counting section 8
3, and the ratio value is automatically changed to a value based on the relationship shown in FIG.

In addition, in the above-mentioned device, the temperature correction section is composed of a temperature detector 21, its A/D converter 22, and a ratio multiplier 23, and the frequency of the multiplied pulse is changed based on the temperature change. However, in the calculation unit 10, a calculation correction unit is provided in the calculation unit 10, and the calculation unit 10 reads out the coefficients of the calculation formula or from the ROM based on the detected temperature data. The same effect can be obtained even if the read address is changed and correction is made for temperature changes.

Further, when the power supply frequency is 50 Hz and 60 Hz, the relationship between slip and torque is different as shown in FIG. In this case, the power supply frequency may be measured, and based on the measurement, the frequency of the multiplied pulse may be changed or the calculation may be corrected in the same manner as described above.

Sagiho! As described above, the present invention is capable of determining the slip for each predetermined rotation angle of an induction motor selected as necessary using a relatively simple circuit configuration, Abnormality monitoring of the device can be easily and reliably performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an embodiment of the temperature correction section of the present invention, and FIG.
．． FIG. 4 is a diagram showing changes in the relationship between slip and torque based on differences in temperature and power supply frequency, respectively. 4: Encoder 5: Frequency division section 6: Control section 7: Multiplier
8: Counting section 9.11: Latch circuit 10: Arithmetic section

Claims (1)

[Claims] 1. A pulse generator that detects the rotation of an induction motor, a power frequency multiplier, and a pulse generator that outputs pulses during a predetermined number of cycles of the pulse output of the pulse generator. An induction motor slip measuring device consisting of a counter that counts the multiplied pulse output. 2. A pulse generator for detecting the rotation of the induction motor, a power frequency multiplier, and counting the multiplied pulse output of the multiplier sent out during a predetermined number of cycles of the pulse output of the pulse generator. An induction motor slip measuring device comprising a counter, an induction motor temperature detector, and a correction section that corrects the frequency of the multiplied pulse output of the multiplier based on the output of the temperature detector. 3. A pulse generator for detecting the rotation of the induction motor, a power frequency multiplier, and counting the multiplied pulse output of the multiplier sent out during a predetermined number of cycles of the pulse output of the pulse generator. Consists of a counter, a computing unit that calculates torque based on the counted value of the counter, a temperature detector for the induction motor, and a correction unit that corrects the calculation of the computing unit based on the output of the temperature detector. However, this is an induction motor slip measurement device. 4. A pulse generator for detecting the rotation of the induction motor, a power frequency multiplier, and counting the multiplied pulse output of the multiplier sent out during a predetermined number of cycles of the pulse output of the pulse generator. a counter, an arithmetic unit that calculates torque based on the counted value of the counter, a power supply frequency measurement circuit, and a multiplied pulse output of the multiplier or correction of the calculation of the arithmetic unit based on the measured frequency. An induction motor slip measuring device comprising a frequency correction section.