Sharif Digital Repository

In a turn-off RCD snubber, the capacitor value is usually optimized in order to minimize the power dissipated in the switch and snubber circuit. However, it may not be the best value of the snubber capacitor from the reliability point of view. In this paper, the capacitor value is optimized based on reliability considerations. Proposed method presents a new design to achieve the maximum reliability for the set of switch and its snubber. Mathematical analysis of the proposed method is conducted in MATLAB environment. Also, the experimental results are presented for validity of the theoretical analysis. © 2018 Elsevier Ltd  

The limited value of the insolated-gate bipolar transistors (IGBTs) blocking voltage is an important issue for applying these devices to the high-voltage power converters. An effective solution is to use a series configuration of these devices in order to achieve higher voltage ratings in addition to save the interesting features such as fast rising time. To reach this goal, acceptable equal voltage sharing for the IGBTs are provided by the series stacking schemes in the normal operation.However, a considerable difference in their voltage level will be occurred in the short-circuit condition. Although the IGBT can withstand the short-circuit current in a defined time, the occurred high... 

Applying series configuration of the insulated gate bipolar transistors (IGBTs) to the pulsed power supplies offers unique features such as compactness and long life time. In the high-voltage pulsed power supplies, a large number of the IGBTs are required to be serially connected. Hence, the safe operating condition provision for the series IGBTs is an important and crucial issue. The effect of the voltage unbalancing factors becomes remarkable when the number of switches in the series structure increases. There are passive and active methods to balance the voltage of the series IGBTs. In both of these methods, an amount of power must be dissipated to remove the effect of the voltage... 

The safe operating condition for the vacuum tubes is very important and critical since they are very expensive and delicate. Providing limited short circuit energy for the vacuum tube and fast transferring from the short circuit to the nominal operation state are absolutely necessary. Extant protection strategies threat the availability of the vacuum tubes. In addition, they cannot completely protect the tube due to the delay of the fault detection system. This article proposes a high voltage (HV) short circuit fault current limiter which can limit the short circuit energy of the system inherently. The proposed structure activates automatically when the current exceeds the predetermined... 

This article proposes a high-voltage fault current limiter (HVFCL) for high-voltage dc power supplies (HVdcPSs) which limits the current of the power supply automatically in the short-circuit fault (SCF). The proposed HVFCL is based on the series-connected insulated gate bipolar transistors (IGBTs). The main achievements of this article are the balanced voltage sharing and a very low value of the short-circuit current near to the load nominal current for the series-connected IGBTs during the SCF. These achievements result in a longer maximum permissible short-circuit time. These achievements are obtained by a control strategy that puts the series-connected IGBTs in a specific operating point... 

Clamp mode resistor capacitor diode (CMRCD) snubbers have a simple and easy implementing structure. They have been widely adopted in the pulsed power supplies to provide a safe operating condition for the series insulated gate bipolar transistors (IGBTs). The main problem of the CMRCD snubbers is their poor performance in the voltage balancing of the series IGBTs. They are essentially overvoltage protectors and clamp the voltage of the IGBTs in a probable potentially dangerous condition. This issue diminishes the expected lifetime of the series IGBTs, where a number of them face a higher level of the voltage than that of the others. The unbalanced voltage of the series IGBTs will result in a... 

The amount of stored energy is an important issue in the low-droop and high-precision pulse generation. Pulse forming network (PFN) simulating an open-ended transmission line seems to be useful due to its minimum stored energy. The drawbacks of the PFN include low-output pulse quality and constant pulsewidth, which limit their applications. Another limitation of generating rectangular pulses using PFN is that half of the charged voltage appears in the output when delivering the entire stored energy to the matched load. This paper proposes a structure of PFN-based pulse generator that overcomes the above-mentioned limitations. For continuous pulsewidth adjustment, a lossless scheme is... 

The lack of turn-off ability makes the spark gap-based Marx generator uncontrollable in terminating the output pulse. In addition, there are some limitations for rise time and voltage gain improvements in the conventional critically-damped Marx design. In this paper, an efficient over-damped design of Marx circuit is proposed, which leads to a shorter rise time as well as a larger voltage gain. A chopping magnetic switch is employed to achieve the desired values of the fall time and full width at half maximum (FWHM). Moreover, adding a DC bias circuit to the magnetic switch provides the ability to adjust the pulse FWHM parameter. Therefore, an output pulse with a shorter rise time, larger...