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    25 kVA 3-Phase Autotransformer, 380V to 220/200V

    5 out of 5 based on 2 reviews | Write a review
    3-phase autotransformer from professional manufacturer. Capacity rating 25kVA, designed to step down high voltage 380 volt to 220/200 volt, applicable AC circuit 50 Hz or 60 Hz, self-cooling or wind-cooled. Dry type auto transformer has copper/aluminum wire winding for selection, 98% high efficiency, competitive price.
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    Delivery date: 6-12 days

    High quality and safety three phase dry autotransformer is 25 kVA power rating, 50/60 Hz rated frequency, step down input voltage 380V AC to output voltage 220V/200V. Winding material copper or aluminum is available, other primary and secondary voltages can be customized.

    Applications: The 3-phase autotransformer can be used in CNC production equipment, SMT, printing machines, electrical discharge machines, automatic plug-in machines, precision measuring equipment, laser cutting machines, plastic molding machines, medical monitoring systems, PCB drilling machines, laboratory equipment, military use Instrumentation control center, etc.


    Model ATO-ASG25KVA
    Phase 3-Phase
    Capacity 25 kVA
    Input Voltage AC 380V
    Input Current 37A
    Output Voltage (Optional) AC 220V, 200V
    Output Current 65A (220V), 70A (200V)
    Frequency 50Hz / 60Hz
    Winding Material (Optional) Aluminum Wire, Copper Wire
    Cooling Method Self-Cooling or Wind-Cooling
    Working Efficiency ≥98%
    Protection Grade IP21
    Waveform Distortion No distortion (compared with output wave)
    Insulation Resistance ≥ 150MΩ
    Wiring Yn0
    Electrical Strength Power frequency sinusoidal voltage 3000V lasts for 1 minute, no breakdown and flicker
    Overload Protection Can withstand instantaneous 2 times the rated current
    Moisture-Proof Type (Optional) Open type, sealed type
    Ambient Temperature -20℃ ~ +45℃
    Altitude ≤ 2500m
    Relative Humidity 0-95%
    Noise ≤35dB (within 1 meter)
    Design Service Life 20 years
    Use Environment No explosion, rain and snow corrosion place, and no gas and conductive dust in the medium that can corrode metal and damage insulation
    Weight (Enclosure Included) 85 kg
    Dimension 550*500*600 mm


    • 3-phase autotransformer has enough power, the wiring is tight and neat, and does not skip turns. Coils adopt insulated H-class enameled wire, with low no-load current and low loss.
    • The 25 kVA dry-type autotransformer has built-in silicon steel sheet, which has good magnetic flux performance, high heat dissipation coefficient and low magnetic loss.
    • The autotransformer uses electrophoresis technology clamps, no burrs on the edges, rounded corners to prevent collisions, and not easy to corrode.
    • Tinned copper tube terminals and rail-type wiring ports are convenient for wiring and ensure that the power-on overload capacity is increased to the extreme.


    25 KVA 3-Phase Autotransformer Details

    25 kVA 3-Phase Autotransformer Schematic Wiring Diagram

    3-Phase Autotransformer Schematic Wiring Diagram

    Tips: Step-down starting of the 3-phase autotransformer.

    The step-down starting of the 3-phase autotransformer refers to the use of 3-phase autotransformer to reduce the starting voltage applied to the stator winding of motor when the motor starts. After the motor is started, the motor is separated from 3-phase autotransformer to operate normally under full voltage. With 3-phase autotransformer step-down starting, the starting current and starting torque of the motor are reduced in proportion to the square of the terminal voltage. Under the same starting current, larger starting torque can be obtained.

    3-phase self-coupling step-down starting circuit cannot be operated frequently. If the start is unsuccessful, the second start should be more than a few minutes apart. After two consecutive starts, the operation should be restarted at least half an hour later. This is to prevent the starting current in the windings of 3-phase autotransformer from heating up and damaging the insulation of the autotransformer.

    Existing reviews of 25 kVA 3-Phase Autotransformer, 380V to 220/200V
    I am interested in the 208Vac to 415Vac step-up in voltage.
    1. For your autotransformers, can I reconfigure the tap/connection point in my lab to achieve a different voltage?

    2. I am interested in the 208Vac to 415Vac step-up in voltage. Can I use your autotransformers in a step up mode?

    3. I noticed that your autotransformers only show either 200Vac or 220Vac for the input, not 208Vac. Is that correct?

    4. For you isolation transformers, I noticed that your copper winding transformers are often heavier than your aluminum winding transformers. This surprises me since copper has much lower resistance and therefore you can use a smaller cross sectional area and reduce weight. Can you explain?
    From: Luke | Date: 26/11/2023
    Was this review helpful? Yes No (0/0)
    ATO Responded
    1. The voltage has been set during production and cannot be changed later.
    2. Autotransformers can increase three-phase 208Vac to 415Vac.
    3. We can customize according to your requirements.
    4. Because copper is denser, which requires more material to achieve the same electrical conductivity.
    While copper's low resistance and high conductivity are advantages, the impact of density makes it weight inferior to aluminum. So copper windings are still heavier.
    Awesome autotransformer!
    Have been using this 3-phase autotransformer for about months. Solid construction. Solid materials. Zero noise. It seems like it could work forever effortless. Good choice. It's pretty good.
    From: George | Date: 28/04/2022
    Was this review helpful? Yes No (0/0)
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