Juicer starting current test solution

The starting current and starting time of the juicer motor when starting and shifting are important parameters to be tested. First, the design, manufacture and installation of the equipment are tested for compliance; second, reference data is recorded for future production, operation and maintenance. The traditional method is to measure the maximum value of the motor when it starts as the starting current value, and the time taken by the motor from starting to reaching stability is the starting time. If the overcurrent and overload protection are judged and set according to such values, it will be very different from the actual situation. At present, in the test of the juicer starting current, a more reasonable algorithm is needed to determine the starting current, and it is generally necessary to test the current signal for up to 8s after starting, and sometimes even up to 2min. This is something that traditional desktop oscilloscopes cannot do, but our PICO USB oscilloscope can perfectly meet this test requirement. Next, we will introduce how Pico oscilloscopes with two different storage depths interpret this test process.

1. Customer Demand

1. It can test the instantaneous current of the juicer when it is idling, adding ice, adding load, and shifting, and the test time is up to 8s.

2 Under different operating functions, the maximum value, minimum value and RMS value of the current can be calculated in real time.

3 The waveform can be post-processed and saved in CSV, TXT or image format.

4 The detected current value can be used for subsequent complex data processing, such as the implementation of a new starting current algorithm.

2 Test setup

1 PicoScope 3204A (or PicoScope 4224)

2 60A AC/DC current clamp

3 60MHz voltage probe (optional)

3 Testing Process

3.1 Test current under no-load condition

This test mainly records the waveform within 8 seconds after the juicer motor is started. The single trigger function of the pico oscilloscope can be used. The difficulty lies in how to select the trigger threshold.

According to customers, their juicers have a sudden start-up pulse at the moment of startup , with a peak value of -23.7V, and then the current tends to be stable at about 8V. We first selected a trigger threshold of -10V, and in the first test, a start-up pulse of about -23.7V was collected (as shown in Figure 1).

However, when we repeated the startup test, we found that we could not collect the startup pulse. What was the reason? After multiple verifications, we found that the juicer did have a very high startup pulse when it was first started, but after repeated startups, the machine was in the preheating state and there was no instantaneous mutation current pulse when it started (the customer was not aware of this problem before). Appropriately reducing the trigger threshold can test a smoother startup waveform. As shown in Figure 2.

3.2 Current detected when the function is in use (freezing without load)

3.3 Current detected when adding load (adding fruit)

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3.3 Current of the juicer when running steadily

4 Experimental analysis

4.1 Impact of different AD resolutions on testing

In this experiment, we used two PicoScope 4224 and 3204A to repeat the above test process and compare the effects of different memory depths and AD resolutions on the test waveforms. The enlarged graphs are shown in Figures 6 and 7. It can be seen that the waveform of PicoScope 4224 is smoother and can show more details.

4.2 Effects of different memory depths on testing

As can be seen from Figure 8, the waveform is normal within 20 seconds after the juicer is started. However, in the time period of 20s to 80s, a spike pulse of up to 10V will appear regularly every period of time (the red mark part). Previously, due to the limitation of the storage depth of the desktop oscilloscope, customers could only collect the waveform within 20 seconds after the motor was started, thus missing some useful information. However, the use of a large-capacity, high-resolution Pico oscilloscope is completely different. It can not only collect data for a longer period of time, but also the high AD resolution can capture more detailed information, thus helping customers find some potential problems.

5 Conclusion

This solution can test the current signal over a long period of time. Users can select the appropriate storage depth and resolution to test according to their needs. In addition to testing the starting current of a juicer, it can also be extended to other similar small household appliances, such as rice cookers, induction cookers, electric kettles, etc.