电工英文考题及答案

1、1. (10 ) Determine the current I and the voltage UAB of the circuit in Figure 1.2. (15 ) Known:. Find 电工技术英文考题（1）Solution:Solution:DC component:AC component:therefore13. (15 ) The circuit in figure 3 is a sinusoidal circuit. Set A1, A2 , and A3 are ideal ammeters. The readings of A1, A2 , and A3 are

2、 2A, 2A, 3A. The load is inductive. Determine the power factor and the active power P of the load.4. (15) For the Figure 4, U2 = 0V. Determine the relationship between US and IS .Solution:Set Set the impedance angle of the inductive load is , thentherefore,According to KCL, , i.e.Solution:25. (15) I

3、n a three-phase three-wire Y-connected system, the three phase load is shown as the figure. The sequence of the symmetric three-phase source is positive. SetDetermine the phase voltages of the three phase load.6. (15) Before the switch K is closed, the capacitor is uncharged. K is closed at the inst

4、ant t=0. Use three factor method to determine iR (t) and uC (t), and draw the waveforms of them.Solution:Using Nodal Voltage Method,thereforeSolution:According to the equivalent circuit at t=0+ , we can findAccording to the equivalent circuit at t= , we can findAccording to the equivalent circuit af

5、ter t=0 , we can findtherefore37. (15) Use pushbuttons, contactors and relays to control the starting and stopping of two three-phase induction motors: M1 and M2. Design the main circuit and control circuit which can satisfy the following requests simultaneously. （1） When the start pushbutton is pressed, M1 is started. 30 seconds later, M2 can be started manually. M2 can rotate either clockwise or counterclockwise.（2） M1 can be stopped only after M2 is stopped。（3） There must have short-circuit