subject: Abb Current Sensor Application [print this page] Abstract: This paper systematically introduces the ABB, the basic principle of current sensors, circuits, model, parameters, installation, calculation and calibration methods, factors and current sensor in power technologies and application prospects of the importance of .
I. Introduction With the expansion of the urban population and the scale of construction, the increase of various electrical equipment, electricity consumption increases, the city often overload the power supply equipment, power has become increasingly harsh environment , on the power of "test" more and more serious. According to statistics, daily, electric equipment have been about 120 times the power problems of various intrusive, electronic equipment from power failures 60% [7]. Therefore, the growing importance of power issues prominent. Originally as a supporting role, more power with less capital investment by manufacturers and researchers, attention, power technology thus developed into a new technology.
Today, small power equipment has been integrated more and more new technology. For example, switching power supply, hard switching, soft switching, parameter regulation, linear feedback regulator, magnetic amplifier technology, numerical control pressure regulator, PWM, SPWM, electromagnetic compatibility and so on. Direct promotion of the actual needs of the power technology continues to develop and progress, to automatically detect and display the current, and over current, over voltage and other hazards happens with automatic protection and more advanced intelligent control with sensor detection, sensor sampling, Power Sensor trend towards protection, testing current or voltage sensors have come into being by the great majority in our country has the power designers, this paper introduces the ABB company's current sensors.
2, current sensor works [1] ABB's current sensor can measure all types of current, from DC to tens of kHz AC, its working principle is mainly based on Hall effect, shown in Figure 1.
When the primary conductor through the current sensor, the primary current I P Produce magnetic field lines , the primary focus on core magnetic field lines around the air gap built into the core of the Hall electrode can produce and the primary is proportional to the size of the magnetic field lines just a few millivolts of the voltage, the electronic circuit can this tiny signal into secondary side current I S , and there is the following relation
Which I S ? Vice-edge current; I P ? The primary current; N P ? The primary number of turns;
N S ? Vice-side coil turns; N P / N S ? Turns ratio, and generally the N P = 1.
Current sensor output signal is the current Vice-side I S It with the input signal (the primary current I P ) Is proportional to I S Generally small, only 100 ~ 400mA. If the output current through the measurement of resistance R M , You can get a current proportional to the size of the primary as a few volts of output voltage signal.
Three main parameters of current sensors [1] [2] [3] [4]
1, the standard rating I PN And rated output current I SN
I PN Current sensor can test that the standard rating, with RMS that (Arms), I PN The size of the sensor model.
I SN Means the current sensor rated output current, typically 100 ~ 400mA, some models may vary.
2, sensor supply voltage V A
V A Means the current sensor supply voltage, it must be provided in the sensor range. Over this range, the sensor does not work or reduce the reliability of the other, the sensor supply voltage V A Divided into positive supply voltage V A + And the negative supply voltage V A -.
3, measuring range I pmax Current sensor measurement range that can measure the maximum current value, measuring range is generally higher than the standard rating I PN . Measuring range can be calculated
Should pay attention to single-phase power supply of sensors, the power supply voltage V Amin Is a two-phase supply voltage V Amin 2 times, so its measurement range than two-phase power supply sensors.
4, overload Current sensor overload See Figure 2. Occurrence of current overload, the measurement scope, the primary current will increase and overload current duration may be shorter and the overload value is likely to exceed the sensor allows the value of overload current values of sensors generally measure does not come out, but not will damage the sensor.
5, precision Hall effect sensor accuracy depends on the standard rated current I PN . At +25 , the sensor accuracy affected by the primary current curve shown in Figure 3, the accuracy can be calculated using the following formula
Which K = N S / N P .
Accuracy must be considered when the current offset, linearity, temperature drift effects.
(1). Offset current I SO Offset current is also called residual current or residual current, it is mainly from the Hall element or an electronic circuit operational amplifier instability caused by working conditions. Current sensors in production, at 25 , I P = 0 case, the offset current has been to the minimum, but left the production line sensor will produce a certain size offset current. Products mentioned in the accuracy of technical documentation has been considered the offset current increases in.
(2). Linearity See Figure 4, the linearity determines the sensor output (secondary side current I S ) And the input signal (the primary current I P ) Within the measurement is proportional to the degree, ABB's current sensor linearity is better than 0.1%.
(3). Temperature drift Offset current I SO Is calculated at 25 , when the Hall electrodes surrounding temperature changes, I SO Will make a difference. Therefore, considering the current offset I SO The biggest change is very important, which can be calculated
Which, CV (Catalogue value) is the current sensor temperature drift performance of the table values, for example: CS2000BR type is, CV is 0.5 10 ----- -4 / , the maximum temperature T max To -40 , rated output current of 400mA, the maximum offset current changes.
