20KVA/50KV Power Frequency AC Withstand Voltage Test Device
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Working Principle:
This series of power frequency AC withstand voltage test complete devices is a single-phase transformer. Through the voltage regulator (external for above 100KVA) inside the operation box (cabinet), an adjustable 0~200V or 0~400V voltage is output to the primary winding of the power frequency AC withstand voltage test complete device. According to the principle of electromagnetic induction, an adjustable high voltage can be obtained at the secondary winding. The wiring principle for a single AC/DC power frequency AC withstand voltage test complete device is shown in Figure 1; a high-voltage silicon stack is installed in the high-voltage bushing, connected in series in the high-voltage circuit for half-wave rectification. When the short-circuit rod shorts the high-voltage silicon stack, the output high voltage is power frequency AC. When the short-circuit rod is unscrewed, the output high voltage is DC.
Two or three power frequency AC withstand voltage test complete devices can be cascaded to obtain higher voltages. The wiring principle for cascaded use of power frequency AC withstand voltage test complete devices is shown in Figure 2. The cascaded high-voltage power frequency AC withstand voltage test complete device has great advantages because the entire device is composed of several single power frequency AC withstand voltage test complete devices. Each single device is small in size, light in weight, and easy to transport and install. It can be connected in series to output several times the rated voltage of a single device for combined use, or it can be separated into several single devices for independent use. In Figure 2, each single power frequency AC withstand voltage test complete device in the first and second stages has an excitation winding A1, C1 and A2, C2. The low-voltage power supply is applied to the primary winding a1x1 of the power frequency AC withstand voltage test complete device I. The output voltages of the single devices I, II, and III are V1, V2, and V3 respectively. The excitation winding A1, C1 supplies power to the primary winding of the second-stage device; the excitation winding A2, C2 of the second-stage device II supplies power to the primary winding of the third-stage device III. The boxes of the second-stage device II and the third-stage device III are at high potentials of V1 and V1+V2 respectively relative to ground, and the boxes are insulated from ground. The box of the first-stage device I is grounded. Therefore, the voltages to ground of the first, second, and third-stage devices are V1, V1+V2, and V1+V2+V3 respectively, and their rated capacities are 3P, 2P, and 1P respectively. |
Capacity Selection
The formula for determining the nominal capacity Pn of the power frequency AC withstand voltage test complete device: Pn=KVn2ωCt×10-9
Where: Pn--nominal capacity of the power frequency AC withstand voltage test complete device (KVA)
Vn--effective value of the rated output high voltage of the power frequency AC withstand voltage test complete device (KV)
K--safety factor. K≥1, when the nominal voltage Vn≥1MV, K=2; when the nominal voltage is lower, a higher K value can be taken.
Ct--capacitance of the test object (PF)
ω--angular frequency, ω=2πf, f--frequency of the test power supply
The capacitance Ct of the test equipment can be measured by an AC bridge. Ct varies greatly and can be determined by the type of equipment. Typical data are as follows:
Simple rod or suspension insulators tens of microfarads
Simple grading bushing 100~1000pF
Voltage transformer 200~500pF
Power transformer <1000kVA ~1000pF
>1000kVA 1000~10000pF
High-voltage power cables and oil-impregnated paper insulation 250~300PF/m
Gas insulation ~60pF/m
Enclosed substation, SF6 gas insulation 100~10000pF
For different test voltages Vn, select different (appropriate) safety factors K. The following K values for different Vn are listed for reference
Vn=50~100KV K=4
Vn=150~300KV K=3
Vn＞300KV K=2
Note: This series of products is manufactured with cascade taps, allowing two or three units to be cascaded to a higher voltage level. For example, two 50KV transformers can be cascaded to output 100KV, and three 50KV transformers can be cascaded to 150KV. Please specify when ordering. In addition, a 5~15KV intermediate tap can be drawn from the high-voltage winding according to user needs, for AC withstand voltage tests of high-voltage motors. Special specifications ofpower frequency AC withstand voltage test complete devices can also be customized.
I.Manufacturer of 20KVA/50KV Power Frequency AC Withstand Voltage Test Complete Device
1.1 Overview of the manufacturer of 20KVA/50KV Power Frequency AC Withstand Voltage Test Complete Device:
Our company, based on the "National Standard for Power Frequency AC Withstand Voltage Test Complete Devices" and the industry standard "JB/T9641-1999", has independently developed and produced lightweight AC, AC/DC dual-purpose oil-immersed and gas-filled (SF6) series transformers. They have the characteristics of small size, light weight, compact structure, complete functions, strong universality, and convenient use. The manufacturer of 20KVA/50KV Power Frequency AC Withstand Voltage Test Complete Device is particularly suitable for insulation strength and leakage tests under power frequency or DC high voltage on various electrical equipment, electrical components, and insulating materials in power systems, industrial and mining enterprises, and scientific research departments. It is an indispensable important equipment in high-voltage testing.
1.2 Product structure of the series power frequency AC withstand voltage test complete devices:
This series of DSYB power frequency AC withstand voltage test complete devices adopts a single-frame iron core structure. The primary winding is wound on the iron core, and the high-voltage winding is on the outside. This coaxial arrangement effectively reduces leakage flux, thereby increasing the coupling between windings. The shell of the oil-immersed power frequency AC withstand voltage test complete device shown in Figure 1 is made into an octagonal structure that fits well with the core assembly, making the overall appearance beautiful and elegant. The shell of the gas-filled power frequency AC withstand voltage test complete device shown in Figure 2 adopts a cylindrical tank container structure, which can withstand a pressure of 0.8Mpa.
2.1 Overview
This series of power frequency AC withstand voltage test complete devices is designed and manufactured according to the test protection requirements of power frequency AC withstand voltage test complete devices. It is divided into manual box type, desktop type, and electric desktop type structures. It has functions such as zero-position protection, overcurrent and overvoltage protection, audible and visual alarm, etc. It is small in size, light in weight, beautiful in appearance, and easy to operate. It is an ideal equipment to match with high-voltage power frequency AC withstand voltage test complete devices.
2.2 Product structure
2.2.1 Box-type structure
The box-type structure is divided into two parts: the inner frame and the outer box. The inner frame integrates all electrical materials and the panel into one, and the outer shell is protective for easy maintenance.
2.3 Working principle:
This series of products consists of two parts: control and measurement. The main contactor controls the power on and off of the voltage regulator input. The opening and closing of the main contactor is controlled by circuits such as the closing stop button, zero-position limit switch, overcurrent and overvoltage relays. The voltage regulator provides an adjustable output voltage to supply the matching product (such as the power frequency AC withstand voltage test complete device) to obtain the required test voltage.
Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.
