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Inverter output phase detection
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Inverter output phase detectionThere are mainly single phase 220V and three phase 380V in frequency converter, and the input phase detection is only found in three-phase products. Figure 1 shows the inverter main circuit, S, T, R for three-phase AC input, when one of the fuses or circuit breaker failure and disconnect, it is considered to be a lack of phase input.
Figure 1 inverter main circuit
In addition to the lack of input phase inverter fault, there is a lack of output, which will directly lead to the lack of motor running. When the motor starts, the motor will not turn up. If the phase is very dangerous lack in operation, the motor current increases 1.2 times, severe fever, acute vibration intensified, easy burning of the motor. By detecting the output current, the inverter can judge whether the three-phase output is short of phase.
Detection method for the phase converter input
When the inverter is not the lack of phase under normal circumstances, UDC voltage as shown in Figure 2, within a power cycle will have six wave head. At this time DC voltage UDC will not less than 470v, actually for a 7.5kW inverter, the C value is generally 900uf, when full load operation, you can calculate the periodic voltage drop is approximately 40V, ripple coefficient does not exceed 7.5%. When the input phase is short, there are only 2 voltage waves in one power frequency cycle, and the lowest value of the rectification voltage is zero. At this point in the above conditions, can estimate the voltage drop is roughly 150V, the ripple coefficient to reach 30%.
Fig. 2 voltage waveform on Udc
Thus it can be seen that in the frequency converter the input phase lack still at run time, capacitance C will be repeated a wide range of charging. This is not allowed, it will inevitably make capacitor damage, resulting in damage to the whole inverter. And if the load is light, although the capacitance will not cause damage, but the DC voltage ripple coefficient compared to normal will increase a lot, and the current transducer with constant voltage control function, which will cause the duty ratio of the oscillation and load current oscillation switch. When the load is heavy, further damage to the rectifier bridge, which makes the inverter fault probability increases, such as the occurrence of the lack of the power supply, due to the single phase high current operation can easily lead to the frequency converter.
One of the most simple way to detect the lack of frequency converter is to use hardware detection, as shown in Figure 3. The circuit voltage level C0 will reflect the R, s, t three-phase input have no lack of phase, C0 voltage decreases when the lack of phase, optocoupler device will not conduction, a signal is high level, the corresponding lack of phase.
Hardware detection method for the input of the inverter with the input of the 3 converter
, of course, you can also input phase lack detection in software. This is because the UDC in normal circumstances, except the DC component, the cycle of the main components of communication for 3.33ms. And in the case of lack of phase, the cycle of the main components of communication will become 10ms, so cycle through the detection of UDC AC component, you can judge whether the lack of phase.
Countermeasures of inverter faults
When the frequency converter is short of fault, it can be checked in the following several aspects: first, whether the input and output of the inverter is normal or not by using the voltmeter or clamp.
Instructions for electrical measurements of the main circuit are shown in table 1.
Table 1 electrical measurement of main circuit
(1) check whether the input and output circuit of the inverter is normal.
Many faults of frequency converter is derived from the periphery circuit, such as circuit breaker, contactor, a reactor and a filter, only to ensure that periphery circuit is correct, in order to make the converter work in a safe and reliable electrical environment.
(2) check the main circuit of the inverter, including the rectifier bridge, IGBT and drive plate.
For lack of phase fault, Emerson inverter EV/TD series fault code shows E008 (input side), E009 (output side missing). Fault location as shown in Figure 4 and figure 5.
Fig. 4 the fault location of the input side of the Emerson inverter
双语对照
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