DESIGN AND SIMULATION OF A HIGH VOLTAGE DC (HVDC) GENERATOR
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DESIGN AND SIMULATION OF A HIGH VOLTAGE DC (HVDC) GENERATOR
Saif M. AL-Rawahi * Ramzi A. Abdul-Halem * Initial Campus, Birkat Al Mouz: P.O.Box:33, PC: 616
*email: [email protected]
Abstract. The paper deals with the design and simulation of a Four – Stage Cockcroft-Walton High Voltage DC generator. Exceptional consideration is taken for the needs of the expected experimental hardware study. The transformer is eliminated for reducing the size and cost of the circuit and additional consideration is taken for the circuit main components. They are chosen reliant on the expecting load current, output voltage and the experimental prototype.
Keyword. Multi-Stages, Diodes-capacitors, DC Voltage generator, Cockcroft-Walton multiplier
INTRODUCTION
DC voltages are mostly used for pure scientific research work and in the industry level the principal application of the DC high voltage is in testing of cables with a relatively large capacitance which will takes a very large current if it is tested with AC voltages [1]. High voltage DC is necessary in many electrical engineering and applied physics applications such as power supplies, X-ray units, TV sets, CRTs tubes, Oscilloscope and Photomultiplier tubes are used in nuclear industry for detection of radiation [2].
The In this study, the proposed high voltage DC generator is based on the Cockcroft-Walton voltage multiplier, which studied in several research works [1-6], converts AC or pulsating DC electrical power from low voltage level to a higher DC voltage level. This circuit is an electronic circuit consisting of a cascading network of capacitors and diodes. It was named after the John Douglas Cockcroft and Ernest Thomas Sinton Walton [3]. The Cockcroft-Walton or Geinacher design is based on the Half-Wave Series Multiplier, voltage doubler [6].
METHODOLOGY
The research work deals firstly with the design, and simulation of a Cockcroft-Walton cascaded Diode-Capacitor four-stage high voltage DC generator. Secondly, the designed and the simulated circuit with the necessary components will be utilized to build the hardware circuit of the generator.
For performing the necessary stages for designing, simulating and developing of the proposed DC power supply, the following procedure will be followed up:
Circuit diagram
The required circuit for building the proposed four-stage, diode-capacitor AC to DC voltage is shown in Fig.1.
Fig.1: AC/DC four-stage, cascaded diode-capacitor AC to DC high voltage generator
D1 D2 D3
D4 D5
D6 C1
C2 C3
C4 C5
C6 Vs
C7
C8
D7 D8
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Due to the hardware of the expected practical work reasons, an AC power source with voltage 220V and frequency 50 Hz is used directly without using any transformer. The other components, capacitors and diodes will be chosen depending on the design general criterion as it will be seen later.
Design Criteria
Capacitor Selection
Normally, the size of capacitors use in the multiplier is selected depending on the frequency of AC power supply frequency. Thus, capacitor for low frequency will be in range of 1.0 to 200 μF. While those for high frequency utilization will be in the range of 0.02 to 0.06 μF, [4]. The voltage rating of the capacitor is determined depending on its capability of withstanding a maximum voltage depending upon the number of stages used in the multiplier. Generally, the voltage rating of the selected capacitors will be approximately twice that of the actual peak applied voltage, [4].
Diode Selection
The selection of diode depending on some basic device parameters which are listed below and are normally given in the data sheet of the device, [4]:
o Repetitive peak reverse voltage o Frequency of the input signal o Peak forward surge current o Forward current
o Forward voltage
Frequency of input signal
While selecting rectifier diode, the frequency of input signal to multiplier circuit must be taken into account. For symmetrical input signals, the device chosen must be capable of switching at speed faster than the rise and fall times of the input. If the reverse recovery time is too long the efficiency and regulation of the device will suffer, [4].
As per the previous general design criteria and the practical hardware work requirements, the high voltage generator selected elements data and specifications, are recorded in Table 1.
Table 1: Data and specifications of the designed high voltage generator parameters
SIMULATION RESULTS AND DISCUSION
As a result of the previous designing procedure of the high voltage generator parameter, the circuit shown in Fig. 2 will be making use firstly for the simulation purpose and secondly for the hardware work in the laboratory.
Parameter Value
Stages 4
Power Supply Voltage (V) 220 V
Power Supply Frequency(Hz) 50 Hz
Capacitance ( uF) 0.01μF
Diode IN4007G
3
Fig. 2: Deigned circuit diagram used for simulation of the high voltage generator
The simulation work has been done using Multisim and Word software program version 7. Figures 3 and 4 represent the simulated result for the voltage versus time for the four stages. Figure 3 showing both transient and steady-state responses. It is clear that the voltage will increase in increasing the number of stages.
Fig. 3: Transient and steady-state responses of the generated HDDC versus time for the four stages
Figure 4 provides individually, the steady-state response intended for showing the result of increasing the generated DC voltage on the ripple voltage δv.
Fig.4: Steady-state response of the generated HVDC versus time for the four stages
Figure 5 is provided for displaying the effect of the input signal frequency on the output DC voltage generated. For showing that influence the HVG has been simulated for a range of frequency between the 50 to 5 KHz with constant value for the capacitor. The result for the four stages indicates very miner increase in the value of the generated DC voltage.
D1 1N4007G
D2 1N4007G
D3 1N4007G
D4 1N4007G
D5 1N4007G
D6 1N4007G
D7 1N4007G
D8 1N4007G 0.01µF
C2
0.01µF
0.01µF
C4
0.01µF
0.01µF
C6
0.01µF
0.01µF
C8
0.01µF V1
220Vrms 50Hz 0°
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Fig.5: Output DC voltage for the four stages versus frequency
Figure 6 is offered for screening the variation in the steady-state settling time versus frequency for same value of capacitor. The result for the four stages indicates that there is decreasing in the settling time in increasing of the frequency.
Fig.6: Steady-state response settling time of output voltage versus frequency
Figures 7-9 indicate, for three different values for load current, 13.33μA, 24.75μA, and 153μA and for f= 50 Hz and C= 0.01μF, the variation of the maximum voltage Vmax and ripple voltage δv versus time.
Fig 7: Voltage versus time, ripples for 13.33 μA of load current
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Figure 8: Voltage versus time, ripples for 24.75 μA of load current
Figure 9: Voltage versus time, ripples for 153.33 μA of load current
From figures 7-9, the assessment values for the maximum voltage Vmax, and the voltage ripple δv for the three simulated load currents are listed in Table 2.
Table 2: Simulation assessments values for δv, and Vmax
CONCLUSIONS
Cascaded diode-capacitor, four-stage Cockcroft-Walton HVDC generator has been designed and simulated. Transient and steady-state responses for the output voltage and for the four stages were recorded using MULTISIM. The generator performances through time and frequency variation such as output voltage and settling time have been drawing for long range of frequency using Word version 7.
As well as, the output voltage variation and Vmax and ripple voltage δv have been sketched versus time using MULTISIM. As a future work the designed and simulated multiplier circuit is attended to be built and tested in the laboratory.
REFERENCES
[1] N.Mariun, D. Ismail, K. Anayet, N. Khan and M. Amran. Simulation, Design and Construction of High Voltage DC Power Supply at 15 kV Output Using Voltage Multiplier Circuits. American Journal of Applied Sciences 3 (12): 2178-2183, 2006.
Load current δV(v) V0Max. (kV)
13.33uA 36 2.406
24.75uA 44 2.391
153uA 46 2.376
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[2] Nikhil M. Waghamare, Rahul P. Argelwar. High Voltage Generation by using Cockcroft-Walton Multiplier.International Journal of Science, Engineering and Technology Research (IJSETR), Volume 4, Issue 2, February 2015.
[3] Wagner L, Araujo and Tarcisio P.R. Campos. Design of a High Voltage Generator and D-T Fusor Based on Particle Accelerator. 2011 International Nuclear Atlantic Conference-INAC 2011, 24-28, 2011.
[4] C.K. Dwivedi and M. B. Daigavane. Multi-purpose low cost DC high voltage generator (60 kV output), using Cockcroft0Walton voltage multiplier circuit. International Journal of Science and Technology Education Research Vol. 2(7), pp. 109-119, July 2011.
[5] M. S. Naidu, V. Kamaraju. High Voltage Engineering. 4th Edition, McGraw-Hill Companies, 2009.
[6] Engineer Xavier Borg-Blaze Labs Research: http://blazelabs.com/e-exp15.asp
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