The supplier of frequency converter braking unit reminds you that as the most mainstream electronic control equipment in motor control, frequency converter has many advantages such as precise speed and voltage regulation, flexible and diverse control methods, etc. Although the usage of frequency converters is familiar and mastered, many people may not necessarily know the secrets within their internal circuits.
1、 Most of the frequency converters we see are three-phase output, and some people believe that three current transformers should be used internally to detect the current of each phase. However, in reality, 95% of frequency converters use a two-phase current detection method (of course, only two transformers are used), and the current value of the remaining phase is calculated by the frequency converter using operational amplifier circuits based on the measured two-phase currents.
2、 When repairing or dismantling a powered inverter, we do not need to use a multimeter to detect the DC bus voltage. We just need to pay more attention to the power indicator lights in the internal circuit of the inverter. This LED indicator not only displays whether the power supply is normal or not, but also intuitively reflects the leakage of DC bus voltage (actually the voltage of the filtering capacitor) after power failure. When the light goes out, it indicates that the DC bus voltage has dropped below 80V, and you only need to wait for a moment to proceed with subsequent work with confidence.
3、 The switching power supply inside the frequency converter usually outputs several voltage levels, including ± 15V,+24V, and+5V. Among these output voltages, the most important one is the+5V circuit. Because the voltage of this circuit is supplied to the CPU of the "brain" of the frequency converter, once there is a fluctuation in the voltage of this circuit, the frequency converter will inevitably fail to operate normally! That is why the switching power supply part of the frequency converter uses this voltage as the monitoring object.
4、 Due to overvoltage, overcurrent and other faults during operation, it is extremely easy to cause damage to the IGBT/IPM power inverter components of the frequency converter. These components are generally expensive and the genuine inventory rate cannot be reliably guaranteed. In the process of repairing single-phase low-power frequency converters, it has been found through a large number of repair examples that for single-phase 1.5-5.5KW frequency converters, after the internal IGBT and rectifier bridge are damaged, two components from the induction cooker can be used for replacement. As long as the performance of the frequency converter is stable and reliable, and these components are relatively cheaper and easier to obtain, it is a good way to reduce maintenance costs.