江苏春晨电缆有限公司生产，本机的三相输出电流检测电路是很有意思的。由两只电流互感器输出的IU、I号，加到IC7-TL072（运算放大器）的三组电压跟随器的同相输入端上，经放大后输入由D8、D9、D10组成的桥式整流电路上。电压跟随器的使用大大提升了电路的输入阻抗，基本上不取用自电流互感器来的信号电流，提高了电流检测的精度。三组电压跟随器将IU、IV二相电流信号还原为三相输出电流信号。D8、D9、D10的整流电压加到后级IC8的5脚，该级放大器为差分放大器，IC8的7脚输出电流检测信号又输入到IC10后级反相放大器的同相输入端6脚，由7脚输出随变频器输出电流大小变化的信号电压，送入CPU的33脚。
The three-phase output current detection circuit of this machine is very interesting. The IU and IV signals, which are output by two current transformers, are added to the three sets of voltage follower of IC7-TL072 (operational amplifier) on the same phase input end, and then the bridge rectifier circuit composed of D8, D9 and D10 is amplified. The use of the voltage follower greatly improves the input impedance of the circuit, and basically does not use the signal current from the self current transformer to improve the accuracy of the current detection. The three groups of voltage follower revert the IU and IV two-phase current signals to three phase output current signals. The rectifying voltage of D8, D9 and D10 is added to the 5 feet of the post stage IC8. This stage amplifier is a differential amplifier. The 7 foot output current detection signal of IC8 is also input to the phase input of the IC10 post stage reverse phase amplifier with 6 feet, and the output voltage of the output current of the inverter is output by the 7 feet and sent to the 33 feet of the CPU.
可以看出，电压检测电路和电流检测电路信号的输出，也是受IC6-HC00四二输入与非门电路控制的。当IC6的4脚输出高电平时，D14、D16有可能正偏导通，抬高了IC10的1、7脚输出电压；当IC6的4脚输出低电平时，D14、D16反偏截止，IC10的1、7脚输出电压不受IC6的控制。至于IC10受控或不受控于IC6，在什么时间，什么条件下受控于IC6，是由CPU的17、41、37脚输出电压信号决定的。到底这是个怎样的控制过程，须手头有一台康沃变频器，实际通电验证才能得知的。因修理康沃变频器的需要，紧迫和仓促之间测绘了整机电路图，机器一经修复，即被用户取走了，当时情境下，也无法从容上电验证机器是如何对两路检测信号进行控制的。
It can be seen that the output of the voltage detection circuit and the current detection circuit is also controlled by the IC6-HC00 42 input NAND gate circuit. When the IC6's 4 foot output is high, the D14 and D16 may be deflated, raising the output voltage of the 1 and 7 feet of the IC10; when the output of the IC6's 4 feet is low, the D14 and D16 are reversed, and the 1 and 7 foot output voltages of IC10 are not controlled by IC6. As to whether the IC10 is controlled or not controlled by IC6, at what time and under what conditions is controlled by IC6, it is determined by the output voltage signals of 17, 41 and 37 pins of CPU. What kind of control process is this It must have a Cornwall inverter at hand, which can be known by actual power verification. Because of the needs of repairing the Cornwall frequency converter, the whole circuit diagram is plotted between the urgent and the hasty. Once the machine is repaired, the machine is taken away by the user. At that time, the machine can not easily verify how the machine controls the two detection signals.
但我想啊-——通过一些变频器的现场运行，也似乎理清了一些头绪——变频器在起动期间或是起动的一个时间段内，一是因输出电压与频率都较低，二是负载情况不一样，变频器是暂缓电流检测保护电路起控的，或者说将保护阀值升高一点，在起动后或者在起动的后半段，再投入保护信号。起动期间对IGBT模块的过流保护，一般由驱动电路的模块故障检测电路来执行。
But I think - it seems to have clear some ideas through the field operation of some frequency converters - the frequency converter is in the starting period or in a time period of starting, one is because the output voltage and frequency are low, the two is the load condition is different, the frequency converter is the control of the temporary current inspection and protection circuit, or will protect the protection circuit. The threshold is raised a bit, and after the start or in the latter half of the start, the protection signal is input again. Overcurrent protection for IGBT modules during startup is usually performed by the module fault detection circuit of the driving circuit.
