**China supplier Sweep Frequency Response Analysis (Sfra) Test price****Brief introduction**

Winding deformation: Winding deformation refers to the change of the axial or radial size of the power transformer winding under the action of mechanical force or electric force, usually expressed as winding local distortion, drum or shift and other characteristics. When the transformer is subjected to the impact of short-circuit current or in the course of transportation, it is possible to have the phenomenon of winding deformation, which will directly affect the safe operation of the transformer.

Two port network: A two port network is a network with a pair of input ports and a pair of output ports. If the network is composed of a linear resistor, inductance (including mutual inductance) and capacitor elements, and the interior does not contain any independent power supply, it is called a passive linear two port network. When the frequency is high, the transformer winding can be regarded as a passive linear two port network.

Transfer function: A transfer function is the ratio of the Laplace transform of the output of passive two port network to the Laplace transform of the input of passive two port network. The distribution of the poles and zeros of the transfer function is closely related to the internal component parameters, the connection mode and the impedance of the ports.

Frequency response: The relation between the transfer function H(jω) of the network and the angular frequency ω in the sinusoidal steady state. The relation between the amplitude of H(jω) and ω is called amplitude frequency response, and the relation between H(jω) phase and ω is called phase frequency response

Frequency scanning: The frequency of the sine wave excitation signal is changed continuously, and the ratio of the output signal to the input signal is measured at different frequencies, then the amplitude frequency response and phase frequency response curve are plotted.

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**Detection principle**Under the action of the high frequency voltage, each winding of the transformer can be regarded as a passive linear two port network composed of linear resistance, inductance, mutual inductance and capacitance and its internal characteristics can be described by the transfer function H(jω), as shown in figure 1. If the winding deformation occurs, the internal distribution of winding inductance and capacitance parameters will inevitably change, leading to its equivalent network transfer function H(jω) zeros and poles change, make the network frequency response characteristics change.

Detection of transformer winding deformation by frequency response analysis is to detect the amplitude frequency response characteristics of each winding of the transformer and compare the results longitudinally or transversely. According to the difference of amplitude frequency response characteristics, the transformer winding deformation can be judged.

The amplitude frequency response characteristics of transformer windings are obtained by means of frequency scanning in figure 1.We continuously change the frequency f (angular frequency ω=2πf) of the external sine wave excitation source VS i, and measure the ratio of the response terminal voltage V2 and the signal amplitude of the exciting terminal voltage at different frequencies to obtain the amplitude frequency response curves of the winding at the specified excitation and response. In figure 1: L, K and C represent the distribution inductance of the unit length, the distributed capacitance and the distributed capacitance,V1 and V2 represent the excitation voltage and the response voltage of the equivalent network, VS is the sine wave excitation signal source voltage, RS is the signal source output impedance, R is the matching resistance.

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**Main technical parameters**1. Working power supply: single phase AC 220V±10%,50Hz(47~63 Hz)

2. Working temperature: -30ºC~50ºC (Test host)

3. Working humidity: ≤90%RH, No condensation

4. Sweep range: 100Hz~2 MHz (Customizable 10MHz)

5. Frequency accuracy: 0.005%

6. Sweep mode: linear or logarithmic

7. Sweep interval :< 1 kHz

8. Measuring frequency range: -100dB~20dB

9. Sweep excitation output: 20Vpp

10. Detection accuracy: Better than ±0.5dB

11. Output impedance: 50Ω

12. Input port impedance: 1MΩ

13. Data storage format: Excel data format, can be opened in plain text