The main purpose of, exchange of digital programmable variable frequency power supply 

 Digitally programmable variable frequency power supply for power grid simulation, the simulation of the various countries of the world's power grid, and other testing equipment for products powered by the relevant parameters of the test. 

 Second, the exchange of digitally programmable variable frequency power supply selection indicators 

 The basic indicators of the digitally programmable variable frequency power supply capacity, voltage and frequency can be adjusted. Generally typical parameters are as follows: 

 Capacity: 500VA above 

 Voltage: 0 ~ 300V, 600V, 0.1V Step 

 Voltage stability: ≤ ± 1% 

 Voltage measurement accuracy: ≤ ± 2% 

 Frequency: 45 ~ 65 500Hz 

 Frequency stability: ≤ ± 0.1% 

 Waveform distortion: ≤ ± 2% 

 Rated current: P / V (220V, 110V) 

 Current measurement accuracy: ≤ ± 2% 

 Key indicators: capacity, waveform distortion, rated current, the frequency range 

 Third, exchange digital programmable variable frequency power supply selection 

 To determine the load characteristics: ① resistive load; ② inductive load; ③ capacitive load; ④ rectifier load; ⑤ hybrid load. 

 2, to determine the output mode: single-phase, three-phase 

 3, to determine the power capacity: different load characteristics will lead to the impact of the different current load at startup, so the power supply selection must consider the impact of current, otherwise the power supply will not be the normal output. 

 (1) resistive load: load power capacity = 1.1 × rated power 

 (2) resistance flu or RC load: power capacity = 1.1 × load apparent power 

 (3) Motor load: direct starting motor load starting rush current is about 5 to 7 times the rated current start time is normally within 2 seconds. 2 seconds overload of the general power of 2 times, beyond this range, power overload protection. Therefore, taking into account the starting capacity, direct starting of the motor load, the power supply capacity should be 3 times the motor power, or else to take measures to soft-start. 

 (4) rectifier load: the input circuit includes a rectifier diode (or thyristor) and the filter capacitor, if the input loop soft-start device, in the closing moments of the input switch, the load can be regarded as short-circuit, will have a great impact current, leading to power over-current protection. Often the starting impact current, will also adversely affect the load circuit, so the user rectifier load input circuit should be soft starter measures to limit the starting current. 

 Rectifier load current of the pulse current, the current crest factor of up to 3.5 times and therefore have some impact on the output of the power supply output voltage waveform and the long-running, the impact is determined by the load current crest factor, usually, when the load current crest factor> 2:00, power capacity press Select: 
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