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Several important factors affecting the measurement results of power analyzer
Release time:
2022-06-01
In the process of using the power analyzer for testing, sometimes although facing the same signal, there will be large deviation due to different measurement results of the equipment used, even if the same brand of power analyzer is replaced, there may be some differences. At these times, it is often caused by the field test engineers not being familiar with the relevant parameters of the power analyzer. So, what kind of parameters will cause the difference in test results?
1. line filter
for different power analyzers generally have two purposes, one is to avoid aliasing in measurement results, and the other is to adapt to practical application requirements. Manufacturers will consider the effect of harmonics on them and set different parameters. For example, for motor manufacturers, the harmonics of the inverter/controller will not work on the torque output of the motor, line filters are often set to more accurately measure the output efficiency of the motor. Due to the lack of corresponding standards, the filter parameters set by different manufacturers are also different, so there will be great differences in the measurement results.
2. update period
The update period of the power analyzer generally refers to the calculation period. Most of the time, what is needed for measurement is a certain characteristic quantity of the reaction electric parameter, and the calculation of many characteristic quantities cannot be separated from the period, such as the true effective value and the effective value of the fundamental wave. In the process of integration, the selection of the period is relatively important, for example, for a signal with a certain difference in each cycle, when the update cycle is fast, the measurement result may fluctuate greatly, and when the update cycle is slow, the measurement result is relatively stable. Therefore, when the signal changes quickly and needs to accurately capture the signal changes, it is generally recommended to speed up the update cycle, so as to better reflect the real situation of the signal in each cycle, otherwise, the update cycle can be appropriately slowed down. It is worth noting that the update period must be not less than the whole period of the actual signal period, otherwise the measurement result will be completely wrong.
3. Averaging mode
reproduces the average mode to suppress random errors and improve the smoothness and stability of the measurement results. Therefore, if the real signal changes very quickly and the stability is not good, whether the mode is set or not will cause the measurement results at the same time point to be different.
4. Effective Bandwidth
The effective bandwidth refers to the zui high frequency that can be measured and analyzed. Therefore, the effective bandwidth of the power analyzer must be greater than the effective bandwidth of the signal. Otherwise, when calculating the effective value, a certain amount of high-frequency signal will be lost, resulting in a small effective result. Therefore, systems with different effective bandwidths will have different test results. At the same time, also pay attention to the sampling rate and effective bandwidth matching, if the effective bandwidth of the signal is too wide or the sampling rate is too low, then the aliasing phenomenon. Measurements can also be unreliable.
5. measurement system
in actual application, the measurement system is not only composed of power analyzer, but also has front-end sensor. Each level module has its own error. The more front-end measurement equipment is introduced, the greater the deviation of the obtained signal distance from the true value will be. In addition, the front-end sensor also has a problem of matching with the effective bandwidth of the power analyzer. If the effective bandwidth of the front-end sensor is lower than the effective bandwidth of the power analyzer, the effective bandwidth of the entire measurement system will be equal to the bandwidth of the sensor, and the effective bandwidth of the power analyzer will also be suppressed, resulting in waste. Therefore, it is recommended to minimize the equipment access link or calibrate the overall system, so as to control the overall test system error.
6. phase accuracy
for power measurement, because phase affects power factor, the accuracy of phase in AC signal is very high. Some power analyzers have high accuracy of power phase in the industrial frequency band. After deviating from the industrial frequency band, their phase index will be significantly reduced, which will increase the error of power factor and directly lead to the increase of error geometry level of power measurement results. Therefore, engineers need to be able to accurately assess the error effects under different frequency bands, or choose a power analyzer that can achieve accurate phase measurement under the overall coverage of each practical application frequency band.
7. electromagnetic compatibility
in the field industrial environment, the complex electromagnetic environment often interferes with the signal transmission, and the signal received by the power analyzer may deviate from the signal output by the front-end sensor, which directly leads to the difference of the measurement results. Moreover, with the change of the industrial field, the same signal will often have different results, therefore, it is not only required for the electromagnetic compatibility of the acquisition equipment and the power analyzer, but also for the transmission line.
1. line filter
for different power analyzers generally have two purposes, one is to avoid aliasing in measurement results, and the other is to adapt to practical application requirements. Manufacturers will consider the effect of harmonics on them and set different parameters. For example, for motor manufacturers, the harmonics of the inverter/controller will not work on the torque output of the motor, line filters are often set to more accurately measure the output efficiency of the motor. Due to the lack of corresponding standards, the filter parameters set by different manufacturers are also different, so there will be great differences in the measurement results.
2. update period
The update period of the power analyzer generally refers to the calculation period. Most of the time, what is needed for measurement is a certain characteristic quantity of the reaction electric parameter, and the calculation of many characteristic quantities cannot be separated from the period, such as the true effective value and the effective value of the fundamental wave. In the process of integration, the selection of the period is relatively important, for example, for a signal with a certain difference in each cycle, when the update cycle is fast, the measurement result may fluctuate greatly, and when the update cycle is slow, the measurement result is relatively stable. Therefore, when the signal changes quickly and needs to accurately capture the signal changes, it is generally recommended to speed up the update cycle, so as to better reflect the real situation of the signal in each cycle, otherwise, the update cycle can be appropriately slowed down. It is worth noting that the update period must be not less than the whole period of the actual signal period, otherwise the measurement result will be completely wrong.
3. Averaging mode
reproduces the average mode to suppress random errors and improve the smoothness and stability of the measurement results. Therefore, if the real signal changes very quickly and the stability is not good, whether the mode is set or not will cause the measurement results at the same time point to be different.
4. Effective Bandwidth
The effective bandwidth refers to the zui high frequency that can be measured and analyzed. Therefore, the effective bandwidth of the power analyzer must be greater than the effective bandwidth of the signal. Otherwise, when calculating the effective value, a certain amount of high-frequency signal will be lost, resulting in a small effective result. Therefore, systems with different effective bandwidths will have different test results. At the same time, also pay attention to the sampling rate and effective bandwidth matching, if the effective bandwidth of the signal is too wide or the sampling rate is too low, then the aliasing phenomenon. Measurements can also be unreliable.
5. measurement system
in actual application, the measurement system is not only composed of power analyzer, but also has front-end sensor. Each level module has its own error. The more front-end measurement equipment is introduced, the greater the deviation of the obtained signal distance from the true value will be. In addition, the front-end sensor also has a problem of matching with the effective bandwidth of the power analyzer. If the effective bandwidth of the front-end sensor is lower than the effective bandwidth of the power analyzer, the effective bandwidth of the entire measurement system will be equal to the bandwidth of the sensor, and the effective bandwidth of the power analyzer will also be suppressed, resulting in waste. Therefore, it is recommended to minimize the equipment access link or calibrate the overall system, so as to control the overall test system error.
6. phase accuracy
for power measurement, because phase affects power factor, the accuracy of phase in AC signal is very high. Some power analyzers have high accuracy of power phase in the industrial frequency band. After deviating from the industrial frequency band, their phase index will be significantly reduced, which will increase the error of power factor and directly lead to the increase of error geometry level of power measurement results. Therefore, engineers need to be able to accurately assess the error effects under different frequency bands, or choose a power analyzer that can achieve accurate phase measurement under the overall coverage of each practical application frequency band.
7. electromagnetic compatibility
in the field industrial environment, the complex electromagnetic environment often interferes with the signal transmission, and the signal received by the power analyzer may deviate from the signal output by the front-end sensor, which directly leads to the difference of the measurement results. Moreover, with the change of the industrial field, the same signal will often have different results, therefore, it is not only required for the electromagnetic compatibility of the acquisition equipment and the power analyzer, but also for the transmission line.
Next Page
Comparison of different measurement methods
2022-08-16
2022-08-16
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