This application claims priority to U.S. provisional patent application no. The sensitivity of the detector was 0.07 K at a temperature of 303 K and with an accuracy of 2 K over 273 to 773 K. The emissivity calibration was conducted on the sample at room temperature with a thermocouple reading as a reference. >?R@::O 5b Features: Frequency range: 6HZ 100KHZ adjustable. The unit expresses a relative change or an absolute . A generator utilizing the modified cascade circuit design was used, which is based on charging in parallel and discharging in series, is utilized in the generator. The cascade connection structure avoids the unsynchronized operation problem that may cause damage to the switches in the series connection structure and therefore is safer, more reliable, and less costly. Fig. The PWM period is a function of the data in the PR2 register and the value of the Timer2 prescaler (T2CON<1 :0>). HiLetgo 5pcs NE555 Pulse Frequency Square Wave Rectangular Wave Signal Generator Signal Generator Module Stepper Motor Driver DC 5V-15V Powered 60 $699 Get it as soon as Wed, Oct 19 FREE Shipping on orders over $25 shipped by Amazon Siglent Technologies SDG2042X Arbitrary Waveform Function-Generators, 40 MHz, Grey 99 $49900 21 illustrates PWM wave output signals of the trigger signal generator in accordance with one aspect of the present invention. Two independent outputs are available, a 50 Q source that . Table 4.6 Parameters corresponding to the test voltage waveforms. 7 illustrates the discharging process in connection with the circuit shown in Fig. endobj The fast repetitive exponential decay type of pulsed voltage or single high frequency sinusoidal waveforms are not Enter words / phrases / DOI / ISBN / authors / keywords / etc. 3 compares a series connection and a cascade connection, relative to the circuit of the present invention. Sintered tungsten with thorium dioxide had the smallest erosion rate among the materials tested in the experiment. In another aspect of the circuit, the circuit is configured such that the energy storage units are charged in parallel by the DC source. The cycle repeats itself after time T = (T1 + T2) where T is the time period of the square-wave. In relation to food treatment the technology described may be used for example for cold pasteurization by enabling the injection of high voltage pulses into a volume of liquid (such as milk) without the need for warming. The differential voltage of these two improved cascade connection circuits is a high voltage bipolar square waveform or a high voltage three level bipolar PWM waveform. In order to lower cost and increase reliability, a further implementation of the present invention is shown in Fig. +Vsat), diode D1 is forward biased and capacitor C starts charging through resistance R3towards +Vsat and diode D2 is reversed biased. 22 is a block diagram of a bipolar square wave and PWM wave generator. <>/Border[0 0 0]/Contents(Physics)/Rect[502.0264 612.5547 540.0 625.4453]/StructParent 3/Subtype/Link/Type/Annot>> These local drive circuits are important because the characteristic of the local drive determines the characteristic of the IGBT switches. In CSCs the DC term is a regulated current, and DC inductors are selected to provide the current source. The circuit of claim 1, characterized in that each stage includes two diodes to define and protect a charging path and discharging path. The following figure shows such a asymmetrical square wave generator. Square wave generator are generally used in electronics and in signal processing. Dec 15, 2016. The square wave is the special case of rectangular wave. Fig. The two output channels of the trigger signal generator are used to trigger these two circuits. xXKoFW,r{Gqn-62Twk%JN|( Specification: Voltage 5V, can be powered by USB Working current: 40MA Weight: 220g Rest: 105 x 82 x 20mm (L x W x H) Features: 1. T = 2 X 2.303 R1C1 log10 (2R3 + R2/R2) Sec The common exercise is to make the R3 equivalent to R2. In The main function of this low-resistance layer is to provide a good contact between the coil and the core, eliminating possible partial discharge (PD) and hence the erosion caused by the PD. 18 is a block diagram of a CCP module in accordance with an implementation of the present invention. 289 0 obj 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. There is also a need for a square-wave and SPWM-wave generator for more general applications that is operable to generate high voltage pulses that is robust and cost effective to produce. The high repetition rate pulse voltage with high dv/dt transients is known to cause increased dielectric loss, space charge injection or charge accumulation in the insulation, and higher partial discharge activity. c s u s b . An insulation test apparatus characterized in that it comprises at least one wave generator as claimed in claim 1. TimerO interrupt is generated when the TMRO register overflows from a set value to 0Oh. According to the characteristics of the inductor, the inductor can isolate only transient voltage. endobj As the frequency increases, EP, Kind code of ref document: A high voltage output pulse is obtained with 8.1 kV in amplitude and an estimated 405 A of peak current at a load impedance of 20 . The fibreglass board may be made of glass epoxy laminate that has extremely high strength and excellent electrical insulation. Similarly we have designed a Square wave Inverter circuit that is capable of driving 220v device and handles 60 Watt load. of the power supplies for each drive circuit are shown in Fig. The PWM output, which has a time base (period) and a specific time when the output stays high (duty cycle), is shown in Fig. In a test, two generators with different connection structures, namely, series and cascade, where both generators are connected to the same load. %%EOF 24 illustrates a simulated circuit for testing an inductive load. Therefore, although this approach provides a safe method of generating a high voltage pulse using low voltage power electronic devices, it can not be utilized to build a test facility that can generate high voltage square wave and PWM waveforms. With the addition of monostable multivibrators, highvoltage squarewave pulse trains of controllable phase are produced. 11 illustrates a waveform generating stage. Unfortunately, the motor manufacturing industry has neither test standards nor test facilities that addresses the issue of enhanced stresses caused by solid state switching drives. Because VSCs are smaller, lower cost, more reliable, and more efficient than CSCs, they have dominated the motor drive market. 283 0 obj (d), the capacitor C. With the properly selected values of the resistors and the capacitors, a square voltage pulse can be generated by turning the switch on and off. The continuous strikes of fast transient voltage clearly increases the electrical and thermal stresses on the insulation system of the motor coil. The disadvantages of this method are high energy consumption and low output efficiency. The circuit of claim 3, characterized in that in discharging the circuit, the first switches are "ON" and the second switches are "OFF". operated under the stress of the power frequency sinusoidal voltage, but rather under that of a more complex voltage waveform. Each resistor is 600W rated, over the operating temperature of -55 to 150. 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. The PWM duty cycle is determined by (CCPRxL:CCPxCON<5:4>) and the value of the Timer2 prescaler (T2CON<1 :0>). If one or more switches in the IGBT stacks fail to operate simultaneously, all the IGBT stacks would then fail. When the multiple sinusoidal voltages of the various frequencies of PWM waveforms are applied simultaneously to the motor insulation system, some of the frequency-sensitive materials in the laminated insulation system generate more heat under the high frequency harmonic stress. <>stream Table 4.4 Equivalent capacitance and resistance of test objects. High frequency waveform generator circuit diagram The circuit can be used to generate square wave, triangle, or sine wave by programming the pin inputs (A0:pin 3, A1:pin 4). <]/Prev 470002>> In both cases, the voltage at the switch is still a PWM waveform with a peak voltage of 1500 V, which is within the operating voltage range of each stage. For a sinusoidal PWM waveform, the switching frequency of the PWM waveform is the product of the fundamental frequency and the frequency modulation ratio. With specially designed charging and discharging circuits, each stage can generate square wave independently. This generator is capable of producing both positive and negative going square waves with variable amplitude, repetition rate, and width. The output can only put 60mA so if you are driving any capacitance the output will be slow. The generator consists of several cascaded stages and each stage is made of IGBT stacks, capacitor, and wave shaping resistors. For the same reason, the switches in a conventional series chain may not turn-on and turn-off at the same time during switching transients even if the gating signals are applied simultaneously to all the switches. The requirements and functions of the trigger signal generator can thus be described as follows: It can produce square wave and PWM waveform trigger signals according to different settings: the frequency of the square wave and the switching frequency of the PWM waveform needs to be adjustable. 1. The circuit of claim 1, characterized in that the charging and discharging is initiated alternatively. 2 in one embodiment of the present invention. For the PWM wave signal, the fundamental signals of these two output channels (1 and 2 in Fig. The difference between these two output signals is a three level bipolar PWM waveform (M in Fig. Further Implementation of Trigger Signal Generator. Then the equation for the time period can be simplified as T = 2.1976R1C1 0000015003 00000 n of a cable or of an apparatus, for example using partial discharge measurements; Electrostatic testing of components, parts or materials, Modulating pulses with a continuously-variable modulating signal, Duration or width modulation Duty cycle modulation, Circuits therefor, e.g. Fig. For ten stages, the total capacitance is 0.2 F, which is much higher than the capacitance of most test objects. The PWM voltage waveform consists of a group of voltage pulses with a fast rise time and varying pulse widths. Table 4.3. Timer2 is an 8-bit timer with a prescaler and a postscaler as shown in Fig 19. Repeating this process over and over would produce a square wave. The dielectric strength of the board is 550 vpm(Volts/mil) or 21.65kV/mm. By using an avalanche trigger technique the generator is able to produce high voltage double square-wave pulses with variable pulse width and pulse interval time. The circuit of claim 1, characterized in that the energy storage devices are discharged through the wave shaping resistors. They also provide protection against vibration damage. The trigger and control system of the generator of the present invention may be implemented using a microcontroller-based trigger signal generator, local drive circuits, and trigger signal transmission channels. When the switch turns on (as shown in Fig 2 (b)), C, When the switch is on, capacitors Ci and C, When the switch is off as shown in Fig 2. The circuit comprises a plurality of stages, each stage including (a) an input connected to a DC source, (b) a first switch, (c) a second switch, (d) an energy storage device and (e) a wave shaping resistor, wherein the first switch charges the energy storage device and the second switch discharges the energy storage device. Both serve as electrical insulation as well as mechanical protection. Although the results have shown that fast repetitive exponential decay or high frequency voltages have a negative impact on the motor insulation system, these factors may be only part of the problem. This voltage may damage the switch. This is a function (waveform) signal generator designed with1602 LCD screen and intuitive 5 buttons It can produce some specific periodic time function waveform (sine, square, triangle, sawtooth, and pulse wave, etc.) 8. 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. Any electrical or signal related connections between the stages are connected through isolation transformers or optical fibres. 0000008584 00000 n Table 4.7 shows the maximum stable temperature rise of the motor coil under different voltage stresses. The circuit comprises a plurality of stages, each stage including (a) an input connected to a DC source, (b) a first switch, (c) a second switch, (d) an energy storage device and (e) a wave shaping resistor, wherein the first switch charges the energy storage device and the second switch . To obtain enough resolution for a variety of square wave frequencies, the data in the prescaler register OPTION_REG is set according to the range of the setting frequency, as shown in Table. The circuit design described herein enables the generator to produce the stable high voltage square wave and PWM waveforms. The circuit is configured such that by charging the circuit and sequentially switching all of the first switches and then the second switches substantially at the same time, the stages are operable to cumulatively generate as an output high voltage square-waves and SPWM-waves. There are faster drivers, including the capability of driving 2500 pF in 25 ns with 6 A peak drive current. The load current bypasses the wave shaping resistor of "open switch" stage through the freewheeling diode D, As mentioned above, the cascade connection can eliminate or substantially reduce the risk of failure of the switches in generating high voltages. The maximum resolution of the duty cycle is 10 bits. 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 test object had an equivalent capacitance of 500 pF. (Teledyne Semiconductor, Mountain View, CA.). 23 shows the curve of maximum frequency vs. the equivalent capacitance of the test load. Selecting this option will search all publications across the Scitation platform, Selecting this option will search all publications for the Publisher/Society in context, The Journal of the Acoustical Society of America, Highvoltage, fullfloating 10MHz squarewave generator with phase control, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109. 16 is a flow chart that illustrates the TimerO interrupt service routine. Until now, most insulation test methods and test facilities are traditional, which have been derived from the initial design of rotating machinery in which the motors are operated at a single power frequency. Based on the waveform generation mechanism described earlier, the rise time, the pulse width, and the fall time of the waveform are predicated by the values of R, Considering most insulation materials and commercially available pulse capacitors, the value of Ci may be chosen to be 2 F. This comes about when a switch in the chain closes later than the other switches; or if a switch opens earlier than other switches, the total output voltage appears across the out of phase switch, resulting in a damage of the switch. An insulation test apparatus based on the wave generator is also provided. 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. With respect to a reference voltage level SL of a straight line, as a generator 1 rotates, a waveform of the middle point voltage between magneto-resistance elements MR1, MR2 becomes like a sine wave. Additionally, in a laminated insulation system of motor coils, the diversity of the frequency response characteristics of the materials also changes the voltage distribution along the insulation layers. The HV is output from a DC-DC converter that takes 3.7vdc and generates 300vdc. 12 illustrates an IGBT based pulse voltage generator. The trigger signal generated by the trigger signal generator is divided into two interlocked signals; one signal is to control the operation of switches SW] to produce the desired waveform, and another signal is to control the operation of switches SW. 14. Frequency control range 0-12.5, sine wave, triangle wave 5MHZ waveform distortion is more serious, square wave. <>/Border[0 0 0]/Contents( \n h t t p s : / / s c h o l a r w o r k s . The rising and the failing parts of the waveform are also shown in Fig. Fig. The circuit of claim 1 , characterized in that the wave shaping resistors of the stages are connected in series. 2(a), R, First, the capacitor Ci is charged to voltage Vj. This reference discloses a design that is clamed to produce up to 200 kV pulse voltage with a repetition rate of up to 1000 pulses per second (PPS). These units have an isolated/floating output and can be biased with respect to the load or grounded. Table 2 lists the I/O port and pin assignments of the (micro control unit) MCU in the generator. The circuit is very basic. 0 The typical turn-on time is around 93ns, and the typical turn-off time is 490ns. Square Wave Generator with Variable voltage and frequency. When the stop button is pushed, port CO is pulled high, and the generator stops generating the waveform and trips the power supply of the IGBT-based pulse voltage generator. Square wave pulses have been identified as more lethal compared to exponential decay pulses in PEF applications. In this new design, the DC sources in the original cascade connection are replaced by capacitors. 20). In order to obtain a long lifetime, various electrode materials have been experimentally tested. The basic circuit for high voltage square wave and PWM wave generation is shown in Fig. Fig. The signal rate of the channel is one implementation is around 5MBd and the maximum propagation data delay of the optical channel is around 145ns. In summary, the insulation system of a motor that is fed by a voltage source converter is not exposed to the traditional power frequency sinusoidal voltage, but instead to a more complex voltage waveform, which may cause increased voltage stress and thus a higher level of thermal stress on the motor insulation, resulting in the premature failure of the motor.

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