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Product samples for Jiangyin Spark Electronic Technology Co., LTD. Are exhibited in GMPC of ETW Japan .

Address: AIM Bld.1F Asano3-8-1 Kokurakita-Ku Kitakyushu city Japan

Open Time: Monday ~ Friday Tokyo 9:30-17:30 (All Year)

Booth No.: 16

Details: jp.etwgmpc.com

The Function of Transformer
The transformer is the connecting element between the primary system and the secondary system. It can turn the large current in primary system into small current in secondary system which in turn provides energy for current coil of measurement instrument or relay, thus reflect the normal working parameters and malfunctions of electric equipment.

The devices, such as instruments and relays, in the secondary system are isolated with the high voltage ones in the primary system to ensure the safety of the operator. It can also realize the no

rmalization and miniaturization of the devices in secondary system so that these devices come in small and light structures, cheap prices, and easy installation. Remote measurement and control can be performed with low-voltage small-gauge control cables. When the primary system is short-circuited, the transformer can protect the devices in secondary system from large current damaging.

The Working Principle of Current Transformer
Generally, the primary turns of current transformer are less than the secondary ones, so the current transformer can be treated as a converter. The working principle is much the same as that of voltage transformer, and the working condition is similar to the short circuited condition in voltage transformer. The primary side of current transformer is connected into the main circuit, obtaining a tested current I1, while the secondary side is connected with the current coil of an ampere meter or power meter with low internal resistance, obtaining a secondary current I2. The electromagnetic parameters and positive directions are determined by electrical engineering.

The Selection and Calibration in Accuracy of Current Transformer
The accuracy is the maximum error while the primary current is at rated value and the secondary load is within the permissible range. Current transformers with different accuracy shall be used for different measurement instruments. For example, the billing and metering current transformer has accuracy ranging from 0.1 to 0.5, while the ampere meters monitoring the load current of input and output circuit is generally equipped with current transformers with accuracy of 1.0 to 3.0.

The Application Method of Current Transformer
The wiring of current transformer should conform to the principle of series connection. The primary side shall be connected in series with the tested circuit, while the secondary side connected in series with all the instruments loads.

According to the tested current value, proper conversion ratio shall be chosen to minimize the error. The secondary side must be grounded in case that once the insulation system is damaged, the high voltage in primary side may drift into the low-voltage secondary side and cause casualty and equipment accident.

The secondary side is definitely not allowed to be open-circuited.

To meet the needs of failure judgment and fault recording devices of measurement instruments, relays, and breakers, 2-8 secondary-sided current transformer shall be installed in the circuits of generators, voltage transformers, output lines, bus section breakers, by-pass circuit breakers, etc. Large current grounding system generally adopts 3 phase installation, but small current grounding system can use 2-phase or 3-phase configuration depending on the practical condition.

Explanations about the Accuracy of Transformer
The 0.2, 0.2S, 0.5, 0.5S are all the accuracy level for transformer. In normal working conditions, the error of transformer must be kept within the prescribed range.

Current Transformer (For Measurement)
As for the measurement current transformer with accuracy of 0.1, 0.2, 0.5, or 1, while the ohmic value of secondary load is within 25%-100% of the rated load value, The current error and phase error in rated frequency must be kept within the ranges shown in the table below.

Accuracy Current Error (± %) in the Following Rated Current (%) Phase Error in the Following Rated Current (%)
±min ±crad
5 20 100 120 5 20 100 120 5 20 100 120
0.1
0.2
0.5
1
0.4
0.75
1.5
3.0
0.2
0.35
0.75
1.5
0.1
0.2
0.5
1.0
0.1
0.2
0.5
1.0
15
30
90
180
8
15
45
90
5
10
30
60
5
10
30
60
0.45
0.9
2.7
5.4
0.24
0.45
1.35
2.7
0.15
0.3
0.9
1.8
0.15
0.3
0.9
1.8

As for the measurement current transformer with accuracy of 0.2S and 0.5S, while the ohmic value of secondary load is within 25%-100% of the rated load value, the current error and phase error in rated frequency must be kept within the ranges shown in the table below.

Accuracy Current Error (± %) in the Following Rated Current (%) Phase Error in the Following Rated Current (%)
± min ± crad
1 5 20 100 120 1 5 20 100 120 1 5 20 100 120
0.2S 0.75 0.35 0.2 0.2 0.2 30 15 10 10 10 0.9 0.45 0.3 0.3 0.3
0.5S 1.5 0.75 0.5 0.5 0.5 90 45 30 30 30 2.7 1.35 0.9 0.9 0.9

Voltage Transformer (For Measurement)
While the load is within 25%-100% of the rated value, with frequency at the rated value, voltage within 80%-120% of the rated value, and 0.8 (lag) power factor, voltage error and phase error of the measurement voltage transformer must be kept within the ranges shown in the table below.

Accuracy Voltage Error (± %) Phase Error Permissible Range of Primary Voltage Permissible Range of Secondary Load
± ' ±crad
0.1 0.1 5 0.15 (0.8-1.2) U In (0.25-1.0) S n cos φ 2 =0.8 (lag)
0.2 0.2 10 0.3
0.5 0.5 20 0.6
1 1 40 1.2
3 3 Not specified Not specified

Notes: In the cases of multiple secondary coils, due to the mutual effects between the coils, each of them must meet the requirements of the corresponding accuracy in 25%-100% range of rated output while the other coils works in 0-100% ranges of rated output values. We can perform tests only on limit values to provide an effective testing result. If there are only occasional fringe loads, the effect on other secondary coils can be omitted.

Current Transformer (For Protection)
The accuracy of protection current transformer is rated in percentage by the maximum permissible composite error under rated accurate limit value of primary current. It is suffixed with a letter P which means protection. There are 5P and 10P standard accuracy for current transformer. For example, the 5P10 accuracy means that when the primary current is 10 times of the rated primary current, the composite error of the coil can be less than 5%. As you can see, the later number 10 is the accurate limit coefficient. The error limits are listed below.

Accuracy Current Error (%) in Rated Primary Current Phase Error in Rated Primary Current Composite Error (%) in Rated Primary Current
' ±crad
5P 10P 1 3 60 - 1.8 - 5 10

Voltage Transformer (For Protection)
The accuracy of protection voltage transformer is rated in percentage by the maximum permissible voltage error while the voltage ranges from 5% of rated voltage to the corresponding limit voltage to the rated accurate voltage coefficient. It is suffixed with a letter P which stands for protection. There are 3P and 6P standard accuracy for protection voltage transformer. The error limits are listed below.

Accuracy Voltage Error (± %) Phase Error
± ± crasd
3P 6P 3.0 6.0 120 240 3.5 7

Notes: In the case of transformer with two separated secondary coils, due to their mutual effects, the user should specify the output range on each coil. The upper limit of each output range must comply with the standard rated output value, and each coil must comply with its own accuracy requirements within the output range while the other coil can be loaded within 0 to 100% of the output upper limit value. Tests can be only performed at limit values to provide an effective result. If the range is not specified, the output range of each coil is within 25% to 100% of rated output.

Main Products
  • 260 OHM Mini Voltage Transformer The 260 Ohm mini voltage transformer is a voltage transformer product with high voltage conversion accuracy of 0.1 or 0.2. In rated working condition, the currents in the input and the output circuit are both 2mA, but the output voltage is distinctly lower than the input voltage...
  • 10A Zero Phase Current Transformer The 10A zero phase current transformer is applied to small current monitored circuit. When the monitored circuit fails, it can turn 10A input current into zero phase current ranging from 10mA to 1,000mA and control the switching of circuits. It has high sensitivity and ...