All-In-One Low Voltage Electrical Test
Inductance (L)/Leakage Inductance/Turn Ratio/Resistance (DCR)/Resistance (R)/Balance/Capacitance (C)/Short Circuit.
Automatic Balancing Bridge & 4-Wire DCR Test (DC Resistance)
Check if the winding tension is improper for Transformer.
Turns ratio is an important parameter in transformer.
Ideally, we can get the turns ratio by compare the input and output voltage. However, there are many parameters that might affect. So, there are some different ways to detect turns ratio.
Detect capacitance to make sure the insulation between winding position and winding coil is enough
The winding coil on the transformer include distributed capacitance, it usually distribute between winding coil.
Capacitance is usually represented by the capacitance by one winding to another winding in an equivalent circuit.
Cs and Cp is an equivalent capacitance in series or parallel in equivalent circuit.
D value is the ratio with AC resistance and capacitance, The lower the D value, is better.
Test leakage by LCR balance bridge
When the instrument connect a primary coil with the transformer and the secondary coil is under open status, the test result L= Lp on primary coil + Leakage Current.
→The leakage inside the instrument must short the secondary coil in the transformer.
A ideal secondary coil’s voltage will be 0V in short status. The voltage on both side of primary coil will be 0V. The inductance from primary coil will be the real leakage current.
5265 offer 100mA DC Bias Current to fulfill Netcom transformer product.
The purpose of detect DC bias is to make sure the specification of coil winding and magnetic saturation.
The way we detect is put DC signal on AC signal. The DC signal will cause DC bias on inductance of the transformer. It might also cause magnetic saturation on transformer.
Increase inductance by high magnetic conductivity and decrease the turns to minimize the size and raise the efficiency for inductance magnetic coil transformer. Because of the restriction of the permeability material, magnetic flux can’t be unlimited increasing. When it reach the limited, no matter increase the turns or current, the magnetic flux won’t increase. Meanwhile, it will meet the magnetic saturation especially under DC current. The AC current will not cause any change in magnetic flux. The transformer will loose the inductance feature.
The harm of magnetic saturation
The magnetic saturated transformer will overheat under low voltage and cause damage by time.
It may cause explosion under high voltage.
The inductance of primary winding will obliviously decrease on saturated transformer. Meanwhile, the power consumption on DCR and inner MOSEFT will increase rapidly. This may cause the damage on MOSEFT.
Why do we need to test 8mA for Netcom transformer
There is an test item that focus on open circuit inductance. Must input 8mA DC Bias, frequency 100kHz, voltage level 0.1V sine wave, and inductance>350uH.
While the Netcom transformer is working in the LAN, positive and negative polarity rectangular pulse will create DC bias less then 8mA. This bias will make OCL decrease and cause rectangular pulse error.
Recently, NetCom transformer not only transmit data but also DC voltage far to couple meters away(POE system). POE current is a big energy that reduce the inductance in the coil. This phenomenon will inhibit the transformer’s ability of control electromagnetic interference.
|Built-in Meter Mode|
|Simultaneously display four parameters|
|Basic accuracy||up to ±0.1%|
|Open circuit/short circuit function|
|RS-232, Handler, LAN, USB Host , Handler|
|Pneumatic fixture F5620 built-in 100mA DC Bias|
|USB Host storages can storage setting files, data and capture the screen|