What Is an Isolation Transformer?

Isolation transformer refers to a transformer with electrical isolation between the input winding and the output winding. The isolation transformer is used to avoid accidentally touching the charged body at the same time. The isolation of the transformer is to isolate the currents of the primary and secondary windings. In the early days, it was used by the European countries in the power industry, and was widely used in electronic industry or industrial and mining enterprises, machine tools and mechanical equipment for general circuit control power, safety lighting and indicator power.

Isolation transformer is a safety power supply, generally used for machine repair, maintenance, protection,

The main function of the isolation transformer is to completely isolate the electrical of the primary side and the secondary side, and also isolate the circuit. In addition, the high-frequency loss of its core is used to suppress the introduction of high-frequency clutter.

Transformer core magnetic flux is related to the applied voltage. The excitation current in the current does not increase as the load increases. Although the core will not saturate when the load increases, it will increase the resistance loss of the coil, exceeding

Isolation transformer is a safety power supply, generally used for machine maintenance, to protect, protect from lightning and filter. Isolation transformer primary and secondary voltage can be customized according to requirements. The output of the isolation transformer is completely "open" isolated from the input.

The principle of the isolation transformer is the same as that of the ordinary transformer. All use

Input voltage: 380V

Input current: 15.2A

Number of phases: three phases

Output voltage: 660V

Output current: 8.7A

Rated capacity: 10KVA

Frequency: 50Hz

Model: STS-SG-1KVA

Application: Isolation

Rated power: 50/60 (KVA)

Efficiency (): 98%

Voltage ratio: 400/220 (V)

Shape structure: vertical

Cooling method: natural cooling

Moisture-proof method: open

Number of windings: double winding

Core structure: heart

Cooling form: dry type

Core shape: stepped

Frequency characteristics: low intermediate frequency

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Ordinary isolation transformers have no direct electrical connection between the primary and secondary windings, so the general power transformer has the function of potential isolation regardless of the ratio, and the isolation transformer can isolate a higher potential difference. It is widely used in AC power lines and communication lines to isolate ground loops and effectively suppress common mode interference in the low frequency and audio ranges, but it cannot suppress differential mode interference. Signal and pulse isolation transformers are also widely used in the audio-to-video range, used to interrupt the ground loop, to achieve functions such as coupling AC, isolating DC components, and impedance matching. Because of the distributed capacitance between the primary and secondary sides of the isolation transformer, the impedance of the ground loop is reduced. When for some reason, the potential at point B rises and an interference voltage en occurs, high-frequency common-mode interference can be coupled from the primary side to the secondary side.

The shielded isolation transformer inserts a metal shielding layer between the primary and secondary sides of the isolation transformer. The shielding layer divides the capacitance between the primary and secondary sides into two, which plays a shielding role. If the metal shield is connected to the transformer ground, common mode interference from the primary side is bypassed by the shield impedance before reaching the secondary side. If the metal layer is connected to the input of the transformer primary side (connected to the regulator tap or the ground terminal and the neutral terminal when there is a regulator tap), the differential mode interference from the primary side is also shorted by the shield layer before reaching the secondary side.

Double-shielded isolation transformer When common mode and differential mode interference occur on the primary side, connect one layer of shielding to the primary side to reduce differential mode noise, and connect another layer of shielding to the reference plane or ground of common mode interference To reduce common-mode noise. The isolation transformer case is also connected to the safety ground. The connecting wire of the shielding layer must be short and reliable, otherwise the shielding effect will be significantly reduced at high frequencies.

Triple-shielded isolation transformers When higher isolation requirements are required, triple-shielded isolation transformers are optional. The connection methods of the three different shielding layers depend on the installation method of the transformer and the grounding conditions. Generally, the transformer is installed on the partition of the equipment rack or the partition wall of the shielded room, and the rack is connected to the equipment's safety ground wire. The input power is safely disconnected and protected by an insulation tube.

Requirements for isolation transformers Isolation transformers used in electronic equipment in substations and power plants should be selected in accordance with national standards for equipment. Isolation transformers for power supplies should meet the following indicators: Rated voltage: 220V ± 20 %; Rated current: selected according to the input maximum operating current of the device plus 50%; Insulation resistance:> 10M ; Power frequency withstand voltage: 2500 V, 1 min, leakage current <10mA; High frequency interference suppression : Common mode 2500 V (1 MHz attenuated oscillatory wave) rejection> 60 dB, differential mode 1250 V (1 MHz attenuated oscillatory wave) rejection> 40 dB. The size of the leakage current of the isolation transformer and the shielding effectiveness are selected according to the needs of different equipment applications. ^[4]