12. Activity points. As evident from Table 4.3, the rise time and fall time remain at almost the same level for different peak values of the output voltage. The idea is to generate a square wave first. In order to calibrate high voltage dividers,a square wave generator was constructed and its maximum output voltage was 10 kV.The generator consisted of a DC high voltage source,a pulse forming line(PFL),a spark switch filled with pressurized nitrogen and a pulse transmission line(PTL).Both PFL and PTL were made from the cables with wave impedance of 50 .The length of the PFL was 10 m . The transmitter is connected to the trigger signal generator, and the receiver is a part of a local drive circuit. The maximum voltage overshoot amplitude is defined as [V. In the test, a FLIR-SC500 infrared camera with an emissivity spectrum between 7.5 and 13 m was used to measure the surface temperature of the coil. An inductor is used to isolate the DC source from the high voltage output at the moment when the IGBT stacks are turned on. According to the IEEE standards for stator coils, the power frequency AC test voltage is 1000 V. Voltage-Endurance test: The voltage duration test is designed for the stator coil of large motors and generators. endobj operated under the stress of the power frequency sinusoidal voltage, but rather under that of a more complex voltage waveform. US9608613B2 - Efficient high voltage square wave generator - Google 16 is a flow chart that illustrates the TimerO interrupt service routine. Instead of a common high voltage DC source to charge the capacitors in all stages, a second IGBT switch SW, Therefore the total operation of the circuit of the present invention is operable to initiate two processes; namely, charging and discharging, which are alternatively controlled by two groups of the switches, SWi (also referred to as the first switches) and SW, During the charging process, switches SWi in all stages are off, and the switches SW, During the discharging process, the switches SW, Both charging and discharging processes are controlled by a microcontroller-based trigger signal generator. . In simulation circuits used, the trigger signal of one switch in both generators was connected to ground in order to simulate the worst case operation. Table 4.2 shows the maximum switching frequencies for different loads when a 5 k resistor is connected in parallel with the load. Each stage of the high voltage generator has two IGBT switches in accordance with the implementation described; hence, two local drive circuits are needed in each stage to drive the two groups of switches SWi and SW, Significantly, because the electric potential of every stage is not the same, the stages are isolated from each other. The resistance of conductive tape remains the same with the changing frequency. When the frequency is set higher than 38 Hz, the product of the data in the TMRO register and the data in the TimerO prescaler register OPTION REG determines the interval time between two interrupts. 1) Using NOT Gates. Once TimerO is set to timer mode, the TMRO register increments every instruction cycle time multiplied by the prescaler value. These waveforms are transformed into light signals by the optical transmitters. Here we use Teledynes TSC427 power MOSFET driver. The unsynchronized operation only affects the value of the output voltage, but do not cause failure of the switches. Output frequency: up to 20GHz Sample rate: 50 GS/s Memory: 2 GS/channel, 32 GS (Optional) Resolution: 10 bits Table 4.4 Equivalent capacitance and resistance of test objects. Three typical test objects were selected for testing: a sample motor coil bar (13.8 kV rated voltage), a cable termination (14 kV rated voltage), and a motor stator coil (4 kV rated voltage). As a result, the internal partial discharges can be triggered and cause a high temperature rise. As shown in Table 4.1 and Fig. The temperature image was displayed in a 320x240 pixel array. Therefore, the whole generator has zero risk of failure due to unsynchronized operation. Once the PWM duty cycle in each PWM period is calculated, the data for CCPRxL:CCPxCON<5:4> in the pre-calculated discrete sinusoidal data form can be then calculated through the equation (3.6). A microcontroller-based trigger signal generator as described was used to generate the trigger signals for IGBT switches. The circuit of claim 1, characterized in that the circuit is configured such that the energy storage units are charged in parallel by the DC source. The voltage and current ratings are 1700V and 16A respectively. I wanted a clean 100khz. Each buffer unit amplifies the power of the waveform trigger signal and drives ten waveform trigger signal channels. it is asymmetric in nature. Efficient high voltage square wave generator - SYNAPTICS INCORPORATED So, Ci can be neglected in calculating the rise time. Table.l: Characteristics of theToroidal Transformer. Then i built several generators using 2206 and Max038. Therefore, the switches take a different share of the total voltage in the steady-state. When testing with a high inductive load (2 H), the test voltage waveform is a superimposed waveform consisting of a fundamental sinusoidal waveform and PWM wave (Fig. Murata's ultra . A 500 resistor is connected in series with the load in order to limit the output current. Two independent outputs are available, a 50 Q source that . - Review of Scientific Instruments; (USA), A HIGH VOLTAGE, HIGH-SPEED SQUARE WAVE SURGE GENERATOR, Erosion of spark gap of square-wave high-voltage source for ozone generation, SQUARE-WAVE 100-Mc VOLTAGE GENERATOR WITH RISE AND FALL TIMES LESS THAN 1 nsec AND OUTPUT OF 0 TO 8 v, https://doi.org/10.1016/0029-554X(63)90295-7. When an unsynchronized operation problem occurs in the series connection, the total output voltage drops significantly. In order to illustrate the advantages of the circuit design of the present invention, Fig. Square Wave Generator Using Op amp | EEEGUIDE.COM <>/Border[0 0 0]/Contents(Physics Commons)/Rect[137.2383 212.4906 220.3535 224.2094]/StructParent 5/Subtype/Link/Type/Annot>> With the carefully maintained record of periodic measurements, accumulated over months and years of service, this easy method is valuable as a measure of some aspects of the condition of the electrical insulation, such as contamination, absorbed moisture, or severe cracking. TimerO module timer/counter is used for square wave generation. (b) applying pulses generated by the waveform generator to the insulation of the rotating machine and thereby applying transients and enhanced stresses that reflect the conditions of the rotating machine during use. Each stage consists of a DC source, a switch, a diode, and a low inductance wave shaping resistor. 0000003418 00000 n Enhanced thermal stress is thus applied to the motor insulation system, which may lead to failure of the motor. Each resistor is 600W rated, over the operating temperature of -55 to 150. ^h,vsLHvi3%ODOb3j-% )NP'{)e>;B%'2i(b+oau9X3gJAq h aq5~(E65jj,42WeEcw tg?e]Z2DZhl lo:{6WH_lHuHtMte.pz.oH5Hv5Xm:Lw*It}V 3(b), each stage in the generator needs a separate DC source and these DC sources have to be isolated from each other, which increases cost, and the control circuits for all these DC sources are relatively complicated. This square wave generator circuit can be built simply a 555 timer chip and a few resistors, capacitors, and potentiometers. This is because of the on-time which is longer causes a formidable impact on the microorganisms in the food media. 27. In another aspect of the invention, the output if the circuit is controllable by controlling the first switches of the stages. . The circuit of claim 9, characterized in that when the second switches are "ON", the second switches and the diodes form the path for charging the energy storage units in parallel. A variety of techniques have been used to overcome the voltage limitations of power electronic switches and to achieve the high voltages needed by using relatively low voltage switches. Thus, the trigger signal generated from the microcontroller (port Cl or C2) is divided into two interlocked trigger signals in the interlock circuit of the generator; one used to drive SWi and the other to drive SW. 0000008584 00000 n Because the status of the waveform output pins is changed from high to low or from low to high in each interrupt service routine, this interval time is half the cycle time of the square waveform. endobj the exact voltage waveforms which the motors are exposed to when they are fed by voltage source converters. You don't exactly have a clear description of your requirements nor of the resources at your disposal. Fig. Thus, the ability to shield against the electromagnetic interference (EMI) is enhanced. 281 0 obj <>/Border[0 0 0]/Contents()/Rect[72.0 612.5547 211.1221 625.4453]/StructParent 2/Subtype/Link/Type/Annot>> References are contained for HVDC systems, converter stations and components, overhead transmission lines, cable transmission, system design and operations, simulation of high voltage direct current systems, high-voltage direct current installations, and flexible AC transmission system (FACTS). Fig. endobj So theoretically, the maximum switching frequency can reach 1.7 MHz which is far higher than the operating frequency required for the motor insulation testing. Trigger circuits, protection circuits, and electromagnetic compatibility (EMC) should therefore be designed precisely, which means higher cost and lower reliability. Fig. Fig. insulation may contain conductive additives in order to decrease the partial discharge (PD) activity close to the conductors. Because the metal supports are mounted on high insulation strength fibreglass board, the stages are insulated from each other. 13. Square Wave Generator with Variable voltage and frequency. 280 19 The present invention further relates to motor insulation testing and testing systems. This amplifier was born in 1963, at the hands of Fairchild semiconductors, with the mission of making an "all-terrain . c s u s b . In order to generate a good waveform with a controlled fall time, low inductance resistors are selected for wave shaping. The implementation of the present invention is further explained by describing a representative trigger and control system for use in connection with the circuit described. The PWM output, which has a time base (period) and a specific time when the output stays high (duty cycle), is shown in Fig. The PWM period of the PWM wave for the CPPx output can be calculated using the following formula: The switching frequency of a PWM waveform is defined as 1/ [PWM period]. To bridge this gap, this paper introduces a PD testing platform trimmed for high voltage power electronics systems, including a high-voltage (10 kV) square wave generator using supercascode structure with off-shelf SiC devices, and a contactless PD monitor using Super High Frequency (SHF) signatures from the PD event. In contrast, the conductive tape, which is used as a corona protector in the slot, is not sensitive to changes in the frequency. he construction of a highvoltage (up to 1000 V) bipolar metaloxidesemiconductor fieldeffect transistor squarewave generator is described. The following paragraphs explain the temperature profiles observed. 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