Triple Frequency Test Transformer - Yangzhou Darui - Yangzhou Darui Electric Co., Ltd.

Triple Frequency Test Transformer - Yangzhou Darui

Published: 2020-08-26 09:20:51

Category: Induction Withstand Voltage Test Device

Product Description

Triple Frequency Test Transformer

Darui Electric recommends:

The triple frequency test transformer is used for testing power transformers, voltage transformers, and other test objects. In addition to performing external power frequency high voltage tests on the main insulation of fully insulated transformers,, it is also necessary to conduct induced high voltage tests on the longitudinal insulation of transformers and the main insulation of semi-insulated transformers. Its performance is reliable and can well meet the needs of induced withstand voltage tests for transformers and instrument transformers.

Overview Edit

This product is designed to meet the requirements of the triple frequency induced withstand voltage test and partial discharge test in the "Regulations for Preventive Tests of Electrical Equipment".

The induced withstand voltage test for transformers and instrument transformers is an important test to verify whether the product meets national standards. The longitudinal insulation induced test of winding layers, turns, sections, and phase-to-phase insulation is an important item to assess whether the winding meets requirements. In order to increase the winding test voltage without causing excessive saturation of the transformer or instrument transformer core leading to excessive excitation current, the test frequency needs to be increased, generally to 100Hz-400Hz.

There are multiple methods to obtain a 100Hz-400Hz power supply, among which the more applicable ones are: ① Three variable frequency generator sets (100Hz-400Hz); ② Three single-phase transformer combinations (150Hz), and the most convenient is the second method.

Three single-phase transformer combination method: The primary side is star-connected, and the secondary side is open delta. When the core is not saturated, the main magnetic flux it produces must be a flat-topped wave. Since the flat-topped main magnetic flux contains a large component of third harmonic magnetic energy Φ3, and the third harmonic magnetic flux frequency f3=3f1, the main magnetic flux induces a third harmonic phase potential.

Since the primary side is star-connected and the secondary side is open delta-connected, the core operates in a saturated state, and the no-load current I presents a peaked wave. In addition to the fundamental wave, it also contains higher harmonics. Among the higher harmonics, the amplitude of I is relatively large. Due to the open secondary, the three-phase fundamental components cancel each other out, leaving only the third harmonic output.

The SFQ triple frequency power generator utilizes the saturation characteristics of the magnetic circuit to extract the third harmonic voltage, which has the largest component among harmonics, as the power source for the generator. It is used for frequency doubling and voltage doubling tests on turns, sections, and layers of inductive coil type electrical products such as transformers and instrument transformers, to assess the insulation strength and withstand voltage level of the coils.

Principle Edit

According to national test standards, the induced test voltage for power transformers and voltage transformers is generally considered to be 2-3 times the maximum working phase voltage. As is well known, when a transformer operates at rated frequency and rated voltage, the core is close to saturation. If a test voltage greater than the rated voltage is applied across the winding of the tested transformer using a power frequency supply, the no-load excitation current will increase sharply to an unacceptable level. From the relationship of induced potential, it can be seen that in order to apply a test voltage greater than the rated voltage without saturating the core, the method of increasing the power supply frequency can be adopted, and a power generator with a frequency greater than the multiple frequency must be used.

Characteristics Edit

Technical Parameters

1. Input voltage: Three-phase 380V, 50Hz;

2. Output voltage: 50-500V (max 750V), 150Hz; 100-1000V (max 1500V), 150Hz;

3. Capacity: 1-1000KVA;

4. Waveform: Sine wave, distortion less than 1%;

5. Working power supply: Three-phase AC 380V ±10% 50Hz

2. Rated capacity: 3KVA-30KVA (optional)

Design Description

This product is designed according to the People's Republic of China electric power industry standard DL/T848.4-2004 and the "Regulations for Preventive Tests of Electrical Equipment" issued by the former Ministry of Water Resources and Electric Power in January 1985, to meet the requirements of the power system for frequency doubling induced withstand voltage test equipment for high voltage voltage transformers. It is widely used for AC withstand voltage tests of series-excited voltage transformers at 35-220kV levels in power systems, to assess the main and auxiliary insulation strength of the transformers. It can also be used for induced tests on windings of motors and small transformers, and can also be used as a 150Hz power supply for short-term operation.

Technical Indicators

Input voltage: 380V 50Hz sine wave

Output voltage: 250V-1000V 150Hz waveform distortion ≤5%

Output capacity: 3kVA, 5kVA, 10kVA, 20kVA, 50kVA

No-load operation time ≤5 minutes

Load operation time: 40-60s

Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.

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Product Details

Triple Frequency Test Transformer - Yangzhou Darui