Variable transformer

REO variable transformers – a constant sinusoidal wave form in every application

A variable transformer is used if it is essential that output voltages are adjusted with a constant sinusoidal wave form.

The REO variable transformers create no interference or harmonics and are therefore particularly suited for use in test facilities or research institutes, where high frequency interference could falsify the results.

  • TVR 6500

    Control Unit for Motorized Variable Transformers

    TVR 6500

    Control Unit for Motorized Variable Transformers

    Variable power supplies within the mains voltage and high power range, in most cases, are realized with variable transformers. In general, it is not sufficient to just adjust the voltage or resp. the power, but it is often necessary to keep the adjusted value constant. For this purpose, the variable transformer is driven by a motor which is controlled by a suitable electronic regulator.

    The unit described below, is such an electronic regulator for controlling a DC motor with a permanently excited field.
    The regulator essentially comprises the following main components:
    A power supply, within a voltage range of 80 to 265 VAC, provides the internally required
    operating voltages and the operating voltage for the servo motor.

    The regulator circuit compares the selected set point voltage with the fed back actual voltage, and in case of deviation, produces an error signal, corresponding in amplitude
    and polarity, which is transmitted to the motor drive circuit.
    The actual value input is followed by a precision rectifier which generates the required signal voltage for the regulation circuit from the connected actual value voltage (DC/AC).

    The motor drive circuit, in case of deviation between set point and actual value, receives an error signal from the regulator circuit. This signal is converted into a variable
    pulse-duty factor. The pulse-duty factor determines the adjusting speed of the motor and the direction of rotation of the motor. The input signals of the end limit switches
    are logaically connected to the direction of rotation signals and thus limit the adjustment range of the drive gear.

  • DRTE

    Three-phase variable column-type transformers (auto windings, IP 00)

    • Input voltage: 400 V
    • Output voltage: 400 V
    • Output Current: 8.7 - 208 A

    The REO column-type variable transformers complement the REOVAR series for currents up to 1,000A with a fine-step adjustment of the output voltage at a constant current at the output.

    The waveform of the sine wave is preserved - like that, EMC problems cannot occur over the entire operating range of 0 - 1,000A.  All products in the series come with UL - listed materials .

    The REO construction enables easy handling of the carbon rolls and the spindle - the copper-bevel gear allows a hysteresis-free adjustment of the output voltage even at high adjustment speed of the drive motor. Thus, REO variable column transformers are perfect for high performance adjustment .

    REO-column type variable transformers conform to EN 61558-2-14


  • NLR 7000

    Control Unit for Motorized Variable Transformers

    NLR 7000
    • Input voltage: 230/3x400 V
    • Frequency range: 50-60 Hz

    Control unit for a motor -driven variable transformers

    The REO controller NLR 7000 is used for constant adjustment of  voltage or power at variable transformers .
    The REO controllers NLR 7000.1 -3 is an electronic controller with following control options - all combined in one controller:

    • NLR 7000. 1 = Variable AC control
    • NLR 7000. 2 = variable DC control
    • NLR 7000. 3 = constant voltage + _ 10-30%

    The control electronics of the NLR 7000 controls therefor the three-phase motor of the variable transformer. By programming, various applications are possible. The parameters are set via the LED display - also available with remote control .

    • Protection: IP20
    • Operating temperature: 0 ... + 45 ° C
    • Storage temperature: -10 ... + 80 ° C
    • Rel . Humidity: 80% without condensation
    • Pollution degree: 2
    • Altitude: 1,000 m 0.5% nominal current reduction for each additional 100 m
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