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            2017 - 07 - 28
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            Basic conceptsa. EMC, EMI and EMSElectromagnetic Compatibility (EMC) means the compatibility of products that are in the same electromagnetic environment (electric field and magnetic field). It has 2 ...
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            Magnetic circuitThis article tries to introduce PMDC motor’s magnetic circuit by the most acquainted concepts. It also tries to introduce some characteristics and parameters of the motors by means of ...
            2017 - 07 - 28
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            Basic conceptsMotor is an energy conversion device that converts electric energy into mechanical energy or mechanical energy into electric energy, using magnetic field as media.PMDC motor is an energy...
            EMI testing and its applicable standards

            EMI test and its applicable standards
            EMI tests are usually performed to final product. PMDC motors are usually assembled into final products and tested. Testing items and applicable standards are designated by the customers.
            As far as we know, the final products are divided into 3 types according to different power supplies.
            a. The product connects to grid electricity (China 220VAC, US 120VAC) through power cord and AC/DC adapter.
            The size of such products is small comparing to the length of power cord. Radiated emission out of product surface is much less than the conducted emission along the power cord. Based on such fact, we only test the conducted emission energy along the power cord. There are 2 indexes to evaluate the interfering energy. They are interfering voltage and interfering power reflecting to different frequency range.
            150KHz to 30MHz. Measure the QP and AV value of interfering voltage. Its unit is µV(10-6V).
            30MHz to 300MKz. Measure the QP and AV value of interfering power. Its unit is pW(10-12W).
            Applicable standards are IEC/CISPR14-1, EN55014-1, EN61000-6-3, IEC61000-6-3 and GB4343. Their testing method and limitation are all the same.
            Below chart shows the conducted interfering voltage test result of Chengfang RS-365SHV motor assembled in the heat gun with external chokes and X capacitor. The P value at point 1 is 66.96dBµV. Its QP value is 57.01dBµV, 8.72 dB less than the limitation of 65.74dBµV.
            EMI test and its applicable standards
            Below chart is the conducted interfering power test (30MHz ~ 300MHz) to Chengfang’s soybean milk machine motor. P value of point 1 (30.81MHz) is 34.28dBpW. P value of point 2 (32.7MHz) is 34.35dBpW. As they are both far lower than the limitation, we didn’t measure the QP value at both points.
            EMI test and its applicable standards
            b. Product with built-in batteries
            There is no external physical connection such as power cord or signal line on such product. So we can only measure its radiated emission. In some labs, this test is called space radiation test. Record the electric field strength of electromagnetic interference at designated space position. Measure the value with antenna placed vertically and horizontally. Record the largest electric field strength at each testing frequency point. The unit is µV/m.
            Applicable standards are IEC/CISPR22, EN55022, IEC61000-6-3, EN61000-6-3 and GB9254. Frequency range is 30MHz to 1GHz. Example as per below chart.
            EMI test and its applicable standards
            c. Products that use battery and grid electricity
            Such product can be used solely or, connected to grid electricity / automotive power supply through an adapter. Customers usually require to perform all above 3 tests.

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