System and method for fast calculation of motor electrical parameters

Abstract

The application discloses a system and method for rapidly calculating motor electric parameters, wherein a frequency detection circuit comprises resistors R1, R2 and R3, capacitors C1 and C2 and a comparator U1; the 7th pin of the comparator U1 is connected with a 5V power supply, and the 4th pin is connected with the ground; the 3rd pin of the comparator U1 is connected with the resistor R3, and the other end of the resistor R3 is connected with an output signal of a motor; the 2nd pin of the comparator U1 is connected with the resistor R1, the resistor R2 and one end of the capacitor C2 respectively, the other end of the capacitor C2 and the resistor R1 is connected with the ground, and the other end of the resistor R2 is connected with a 5V power supply; the 8th pin of the comparator U1 is connected with the ground, and the 8th pin is also connected with one end of the capacitor C1, and the other end of the capacitor C1 is connected with a 5V power supply; the 6th pin of the comparator U1 is used as an output; by setting a data group, effective data corresponding to an output signal can be outputted after sampling of at least one data group is completed, and waiting time is reduced.

Description

Technical Field

[0001] This invention relates to the field of electric motors, and in particular to a system and method for rapidly calculating the electrical parameters of an electric motor. Background Technology

[0002] In motor system testing, electrical parameters such as voltage, current, and power are essential for measuring motor performance and calculating motor efficiency. Especially during high-power or stall tests, it is crucial to obtain these electrical parameters quickly; otherwise, irreversible damage may occur to the motor or drive. In traditional motor performance testing, the effective value of the motor voltage (U0) is... RMS ), current RMS value (I) RMS Both the active power (P) and electrical parameters are calculated based on sampled data within a cycle, typically requiring sampling over multiple cycles and obtaining the parameters from the electrical parameters of each operating cycle. However, when the motor speed is very low or close to stall, the frequency F of the input signal is very low, meaning the cycle is long. Using traditional data sampling and calculation methods, it is necessary to collect values ​​from multiple cycles, resulting in long waiting times, which is not conducive to rapid motor testing and can easily damage the motor and other equipment during the testing process. Therefore, a method is needed that can accurately obtain the motor's electrical parameters within a shorter operating cycle. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a system and method for rapidly calculating motor electrical parameters. The system and method are simple in structure, easy to use, and can accurately obtain motor electrical parameters in a short period of time.

[0004] A frequency detection circuit includes resistors R1, R2, and R3, capacitors C1 and C2, and a comparator U1. Comparator U1 uses a TLV3501 integrated chip. Pin 7 of comparator U1 is connected to a 5V power supply, and pin 4 is grounded. Pin 3 of comparator U1 is connected to resistor R3, the other end of which is connected to the motor's output signal. Pin 2 of comparator U1 is connected to one end of resistors R1 and R2, and one end of capacitor C2. The other end of capacitor C2 and resistor R1 is grounded, and the other end of resistor R2 is connected to the 5V power supply. Pin 8 of comparator U1 is grounded and also connected to one end of capacitor C1, the other end of which is connected to the 5V power supply. Pins 1 and 5 of comparator U1 are unconnected, and pin 6 is used as the output. The resistance values ​​of resistors R1 and R2 are equal.

[0005] A method for quickly calculating the electrical parameters of a motor includes the following steps:

[0006] Step 1: Obtain the motor's output signal, measure its frequency, and distort the frequency using the frequency detection circuit described above to obtain the frequency f; the output signal includes output voltage and output current;

[0007] Step 2: Sample according to the set AD sampling rate; where the AD sampling rate is set to 500k, and the number of samples of the motor output signal in one cycle is 500k / f;

[0008] Step 3: Divide the number of samples in each period into y equal parts;

[0009] Step 4: Calculate the voltage data set, current data set, and power data set for each data set;

[0010] Step 5: Based on the nth to (y+n-1)th data groups of each data type, n = 1, 2, 3..., obtain the effective data corresponding to the output signal; where n represents the nth effective data period.

[0011] Furthermore, in step 4, the voltage data group UU ADD The calculation is expressed as:

[0012]

[0013] Where y represents the number of samples in each period divided into y parts; f represents the output frequency of the motor; 500k / yf represents the number of samples in each part after the number of samples in one period of the motor output signal is divided into y parts, U i Sampling data representing voltage;

[0014] Current Data Group II ADD The calculation is expressed as:

[0015]

[0016] Where I i Represents the sampled data of the current;

[0017] Power Data Group (PUI) ADD The calculation is expressed as:

[0018]

[0019] Furthermore, in step 5, the traditional voltage RMS value calculation formula is combined with formula (5) to obtain the following improved result:

[0020]

[0021] Among them UU ADDj This represents the j-th voltage data group; N represents the number of samples in one period, where N is 500kF, U RMSThis indicates the effective value of the voltage.

[0022] Furthermore, in step 5, the traditional formula for calculating the effective value of current is improved by combining formula (6):

[0023]

[0024] Among them, II ADDj I represents the j-th voltage data group. RMS This indicates the effective value of the current.

[0025] Furthermore, in step 5, the traditional active power calculation formula is combined with formula (7) to obtain the following improved result:

[0026]

[0027] Among them, PUI ADDj Let j represent the j-th power data group, and P represent the active power.

[0028] Furthermore, in step 5, the power factor PF of the motor is expressed as:

[0029]

[0030] Furthermore, y = 20 means that the number of samples in each period is divided into 20 parts, one of which has a quantity of 25k / f.

[0031] The beneficial effects of this invention are as follows:

[0032] This invention, by setting up data groups, eliminates the need to wait for the completion of periodic sampling before calculating the valid data corresponding to the output signal. Instead, it can output valid data after completing the sampling of at least one data group, thus reducing waiting time.

[0033] Compared with traditional methods, this invention can obtain more effective data for the same duration of motor output signal, with a richer sample of effective data, and the conclusions obtained are more accurate.

[0034] By grouping data into sets, the cumulative multiplication operation is performed, and the data sets are directly called for the cumulative addition operation. This greatly reduces the amount of calculation of repetitive data, reduces the load on the computing equipment, improves the data processing speed, and shortens the time to obtain motor operating parameters. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the frequency detection circuit in Embodiment 1 of the present invention;

[0036] Figure 2 This is a schematic diagram illustrating the detection frequency using traditional methods.

[0037] Figure 3This diagram illustrates the zero-crossing spikes and noise interference when detecting frequencies using traditional methods.

[0038] Figure 4 This is a waveform diagram of the detection circuit output after comparison in Embodiment 1 of the present invention;

[0039] Figure 5 This is a flowchart of the method according to Embodiment 1 of the present invention;

[0040] Figure 6 This is a schematic diagram of the effective data cycle in Embodiment 1 of the present invention. Detailed Implementation

[0041] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0042] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0043] Example 1:

[0044] like Figure 1 As shown, a frequency detection circuit includes resistors R1, R2, and R3, capacitors C1 and C2, and a comparator U1. In this example, comparator U1 uses a TLV3501 integrated chip. Pin 7 of comparator U1 is connected to a 5V power supply, and pin 4 is grounded. Pin 3 of comparator U1 is connected to resistor R3, the other end of which is connected to the motor's output signal. Pin 2 of comparator U1 is connected to one end of resistors R1 and R2, and one end of capacitor C2. The other end of capacitor C2 and resistor R1 is grounded, and the other end of resistor R2 is connected to the 5V power supply. Pin 8 of comparator U1 is grounded and is also connected to one end of capacitor C1, the other end of which is connected to the 5V power supply. Pins 1 and 5 of comparator U1 are unconnected, and pin 6 is used as the output.

[0045] The resistors R1 and R2 have the same resistance, which is 5.1kΩ in this example; the resistor R3 has a resistance of 1kΩ; and the capacitors C1 and C2 are both 100nF.

[0046] like Figure 2-4 As shown, during implementation, a voltage divider is used through resistors R1 and R2 to ensure that the voltage at pin 2 of comparator U1 is 2.5V. The motor's output signal is passed through the detection circuit in this example. If the motor's output signal is higher than 2.5V, pin 6 outputs a high level; otherwise, it outputs a low level. In traditional detection methods, the frequency of the signal is obtained by detecting the zero-crossing point of the motor's output signal. However, due to signal glitches and interference at the zero-crossing point, errors are easily generated. For high-frequency signals, the impact of these errors is amplified, even affecting the measurement results. Therefore, in this example, the detection circuit distorts the motor's output signal, causing a shift in the zero-crossing point. This eliminates the problem of signal glitches and noise interference near the zero position, and the frequency output by pin 6 of the detection circuit remains unchanged.

[0047] like Figure 5 As shown, a method for quickly calculating the electrical parameters of a motor includes the following steps:

[0048] Step 1: Obtain the motor's output signal, measure its frequency, and distort the frequency using the frequency detection circuit described above to obtain the frequency f; the output signal includes output voltage and output current;

[0049] Step 2: Sample according to the set AD sampling rate; in this example, the AD sampling rate is 500k, where the number of samples of the motor output signal in one cycle is 500k / f;

[0050] Step 3: Divide the number of samples in each period into y equal parts; in this example, the number of samples in each period is divided into 20 equal parts, one of which has a quantity of 25k / f;

[0051] Step 4: Calculate the voltage data set, current data set, and power data set for each data set;

[0052] Step 5: Based on the nth to (y+n-1)th data groups of each data type, n = 1, 2, 3..., obtain the effective data corresponding to the output signal; where n represents the nth effective data period.

[0053] Traditional effective voltage value (U) RMS The calculation is as follows:

[0054]

[0055] Among them U i This represents the voltage sampling data, where N represents the number of samples in one cycle, which is 500kF in this example.

[0056] Similarly, the traditional effective value of current (I) RMSThe calculations for ) and active power (P) are shown in equations (2) and (3), respectively:

[0057]

[0058]

[0059] Where I i This represents the sampled data of the current.

[0060] The power factor PF of the motor is obtained based on the effective values ​​of voltage, current, and active power:

[0061]

[0062] In step 4, the voltage data group UU ADD The calculation is expressed as:

[0063]

[0064] Where y represents the number of samples in each period divided into y parts; f represents the output frequency of the motor; 500k / yf represents the number of samples in each part after the number of samples in one period of the motor output signal is divided into y parts.

[0065] Current Data Group II ADD The calculation is expressed as:

[0066]

[0067] Power Data Group (PUI) ADD The calculation is expressed as:

[0068]

[0069] In step 5, the following is obtained by combining the traditional voltage RMS value calculation formula (1) with formula (5):

[0070]

[0071] Among them UU ADDj This indicates the j-th voltage data group; N represents the number of samples in one cycle, which is 500k / f in this example.

[0072] The following is an improvement obtained by combining the traditional formula (2) for calculating the effective value of current with formula (6):

[0073]

[0074] Among them, II ADDj This represents the j-th voltage data group.

[0075] The following is an improvement derived from the traditional active power calculation formula (3) combined with formula (7):

[0076]

[0077] Among them, PUI ADDj This represents the j-th power data group.

[0078] like Figure 6 As shown, in this example, the frequency of the motor's output signal waveform is 50Hz, resulting in an output period of 20ms. Based on a 500kHz AD sampling rate, the number of samples within one period is 10,000. Dividing the data within one period into 20 equal parts, each part contains 500 samples. Using this method, the first valid data period consists of data samples 1-10,000; similarly, the second valid data period consists of data samples 500-10,500; the third valid data period consists of data samples 1000-11,000…

[0079] In this implementation, there is no need to wait for the periodic sampling to be completed before calculating the valid data corresponding to the output signal. Instead, valid data can be output after sampling at least one data group, reducing waiting time. In addition, compared with traditional methods, this embodiment can obtain more valid data for the same duration of motor output signal. Obviously, the sample of valid data is richer, and the conclusions obtained are more accurate. Furthermore, by using data groups to perform the cumulative multiplication operation in groups and directly calling the multiplied data groups for the cumulative operation, the amount of calculation of repetitive data is greatly reduced, the data processing speed is improved, and the time to obtain motor operating parameters is shortened.

[0080] The above description is merely a specific example of the present invention and does not constitute any limitation on the present invention. Obviously, those skilled in the art, after understanding the content and principles of the present invention, may make various modifications and changes in form and detail without departing from the principles and structure of the present invention; however, these modifications and changes based on the spirit of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A system for fast calculation of electrical parameters of an electrical machine, characterized in that, Comprising The acquisition unit is used for obtaining the output signal of the motor, measuring the frequency and obtaining the frequency f by frequency detection circuit; wherein the output signal includes output voltage and output current; The sampling unit is used for sampling according to the set AD sampling rate; Wherein the AD sampling rate is set to 500k, and the sampling number of the output signal of the motor in one period is 500k / f; The control unit is used for dividing the sampling number in each period into y parts; calculating each part of data to obtain the voltage data group, the current data group and the power data group; obtaining the effective data corresponding to the output signal according to the n~(y+n-1)th data group of each type of data, n=1, 2, 3…; wherein n represents the nth effective data period; The frequency detection circuit includes resistor R1, resistor R2, resistor R3, capacitor C1, capacitor C2 and comparator U1; The comparator U1 adopts TLV3501 integrated chip; the 7th pin of the comparator U1 is connected with the power supply of 5V, and the 4th pin is connected with the ground; the 3rd pin of the comparator U1 is connected with the resistor R3, and the other end of the resistor R3 is connected with the output signal of the motor; the second pin of the comparator U1 is connected with the resistor R1, the resistor R2 and one end of the capacitor C2 respectively; the other end of the capacitor C2 and the resistor R1 is connected with the ground, and the other end of the resistor R2 is connected with the power supply of 5V; the 8th pin of the comparator U1 is connected with the ground, and the 8th pin is also connected with one end of the capacitor C1; the other end of the capacitor C1 is connected with the power supply of 5V; the 1st pin and the 5th pin of the comparator U1 are both empty, and the 6th pin is used as the output; the resistance values of the resistor R1 and the resistor R2 are equal; The voltage value at the 2nd pin of the comparator U1 is obtained by voltage division through the resistor R1 and the resistor R2; the output signal of the motor is detected by the detection circuit; if the output signal of the motor is higher than the voltage value at the 2nd pin of the comparator U1, the 6th pin outputs high level, otherwise, the 6th pin outputs low level; the detection circuit distorts the output signal of the motor, so that the zero crossing point is offset, and the frequency output by the detection circuit 6th pin does not change; The y=20, which means that the sampling number of each period is divided into 20 parts, and the number of one part is 25k / f.

2. A system for fast computation of electrical parameters of an electrical machine according to claim 1, characterized in that, . The voltage data set UU ADD The calculation is represented as: UU ADD = (5) Wherein y represents the number of samples in each cycle is divided into y parts; f represents the output frequency of the motor; represents the number of samples in a cycle of the motor output signal; Current data set II ADD The calculation of the representation of the current data set II is given by II ADD = (6) Power data set PUI ADD The calculation is represented as: PUI ADD = (7).

3. A system for fast calculation of electrical parameters of an electrical machine according to claim 2, characterized in that, The traditional voltage effective value calculation formula is improved by combining formula (5): （8） wherein represents the jth group of voltage data sets; N represents the number of samples in one cycle, N is 500k / f, represents the voltage effective value.

4. A system for fast calculation of electrical parameters of an electrical machine according to claim 3, characterized in that, The traditional current effective value calculation formula is improved by combining formula (6): （9） wherein denotes the j-th group of voltage data sets, denotes the current effective value.

5. A system for fast calculation of electrical parameters of an electrical machine according to claim 4, characterized in that, The traditional active power calculation formula is improved by combining formula (7): （10） wherein denotes the j-th group of power data sets, denotes the active power.

6. A system for fast calculation of electrical parameters of an electrical machine according to claim 5, characterized in that, The power factor PF of the motor is represented as: （4）。

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