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  • New item   -249.13€Transformer three-phase fan motor speed controller | 7.5A | 3x230VAC | surface-mounted | IP54 | Sentera Controls | STR-3-75L10

    Transformer three-phase fan motor speed controller | 7.5A | 3x230VAC | surface-mounted | IP54 | Sentera Controls | STR-3-75L10

    Code: STR-3-75L10
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  • Product description

    Transformer three-phase fan motor speed controller | 7.5A | 3x230VAC | surface-mounted | IP54 | Sentera Controls | STR-3-75L10

    STR-3-75L10 – Sentera Controls transformer speed controller for three-phase voltage-controllable fan motors up to 7.5 A, designed for a 3×230 VAC network. The speed is changed in 5 steps with a knob, and the motor receives a clean sinusoidal voltage.

    Key idea:
    The simplest and most reliable way to control a three-phase fan in a 3×230 VAC network: no electronics in the motor circuit, only an autotransformer and a step switch. The motor runs quietly at all steps.
    What it is for STR-3-75L10:
    This model is intended for high-power fans (up to 7.5 A) – industrial fans in production halls, warehouses, farm buildings or a larger group of fans.
    Max. motor current
    7.5 A
    Control
    5-position rotary switch
    Power supply
    3×230 VAC, 50–60 Hz
    Protection
    IP54, surface mounting

    Operating principle

    The controller is wall-mounted. The 3×230 VAC supply is connected to R, S, T, the motor – to U, V, W, and the unregulated 230 VAC output (L1, N) can supply a damper actuator or indication. According to the datasheet, the supply neutral is not connected to the controller.

    The controller is based on an autotransformer with several taps (steps). When the knob is turned, the motor is switched to another tap, so the output voltage changes in steps rather than steplessly. Regulated output voltages: 0 – 80 – 110 – 140 – 170 – 230 VAC (knob positions 0–5). Position 0 – motor off.

    The output voltage is SINUSOIDAL – without phase cutting as in electronic controllers. Therefore the motor runs quietly even at low speed, does not heat up due to higher harmonics and does not interfere with other equipment. This is the solution for motors that hum or buzz when controlled by an electronic controller.

    Engineer's note: reducing the voltage of an AC asynchronous motor increases slip, so less energy is saved than with an EC fan or frequency inverter. The strength of a transformer speed controller is reliability, quietness and simplicity, not maximum efficiency.

    Benefits STR-3-75L10?
    Quiet, durable and simple three-phase fan control in a 3×230 VAC network – without electronic components in the motor circuit and with an unregulated 230 VAC output for additional equipment.

    Technical specifications

    Product type Transformer three-phase fan motor speed controller
    Manufacturer / code Sentera Controls / STR-3-75L10
    Series STR-3 (3.5 / 5 / 7.5 / 10 / 13 A)
    Supply voltage 3×230 VAC, 50–60 Hz (R, S, T); neutral not connected
    Max. motor current 7.5 A
    Regulated output (U, V, W) 0 – 80 – 110 – 140 – 170 – 230 VAC (positions 0–5), sinusoidal voltage
    Unregulated output (L1, N) 230 VAC, 2 A, 50–60 Hz (in positions 1–5)
    Control 5-position rotary switch with OFF position
    Indication Blue LED – device switched on
    Housing Metal, powder-coated RAL 7035
    Protection class IP54 (EN 60529), for indoor use only
    Operating environment -20…+35 °C, 5–95 % rH non-condensing
    Dimensions A 300 / B 425 / C 185 / D 255 / E 255 mm (letter meanings – according to the datasheet drawing)
    Packaging (L × W × H) 430×310×255 mm
    Weight 18.17 kg (net)
    Compliance LVD 2014/35/EU, EMC 2014/30/EU (EN 61326), WEEE 2012/19/EU, RoHS 2011/65/EU

    Manufacturer documentation

    ✔ Recommended by Elektrotechnikos sprendimai

    Original manufacturer documentation – technical data, wiring diagrams and installation instructions.

    Main functions

    • 5 speed steps – one of five voltages or off is selected with the knob.
    • Sinusoidal output voltage – quiet motor operation at all steps, without electronic hum.
    • Unregulated 230 VAC output (2 A) – for a damper actuator, valve or indicator lamp – switches on together with the fan.
    • Blue LED – you can see at once that the controller is switched on.

    Where is it used?

    • Three-phase fans in 3×230 VAC networks
    • Extract and supply fans in production premises and warehouses
    • Farm and agricultural buildings
    • Process ventilation where quiet operation is important

    On-demand operation

    For the electrician.
    Clear terminal layout: R, S, T – supply, U, V, W – motor, L1/N – auxiliary equipment.
    For the ventilation installer.
    No settings are needed – the steps are selected with the knob on site.
    For the building owner.
    A durable device without programming and without electronic noise.

    Application guide: how it is used in practice

    Typical STR-3-75L10 applications:

    Site What is connected Result Installer's note
    Production hall, 3×230 VAC network Three-phase fan → U, V, W Speed is selected according to season and load Check that the motor is suitable for voltage control
    Fan with damper Damper actuator 230 VAC → L1, N The damper opens when the fan is switched on L1 load – up to 2 A
    Noise-sensitive room A motor that hums with an electronic controller Quiet operation even at low speed Select the steps according to the required air volume
    Several fans in one system Three-phase motors of the same type in parallel → U, V, W All change speed together Sum of rated currents ≤ 7.5 A

    How to select the controller current

    Rated current of the motor(s) Recommended model
    up to 3.5 A STR-3-35L10 (3.5 A)
    3.5–5 A STR-3-50L10 (5 A)
    5–7.5 A STR-3-75L10 (7.5 A) ← this model
    7.5–10 A STR-3100L10 (10 A)
    10–13 A STR-3130L10 (13 A)
    Rule: controller max. current ≥ motor rated current (see the motor nameplate). When connecting several fans – motors of the same type – add up their rated currents. Choose a margin if the motor current is close to the model's limit or the fan often runs at the maximum step.
    When to choose another solution: For a 400 VAC three-phase network – STR-4 series; with TK protection – STRS4; with remote control and alarm – STRA4 or STTA4; for control with a 0-10 VDC signal – STVS4; for a single-phase motor – the electronic EVS-1 or a single-phase transformer speed controller.

    Pros

    • Sinusoidal output voltage – quiet motor operation
    • 5 steps and OFF position
    • Unregulated 230 VAC output (2 A)
    • Metal IP54 enclosure
    • Simple installation without programming

    Cons / limitations

    • Intended for 3×230 VAC networks only – in a 3×400 VAC network use STR-4
    • No TK terminals, remote control or alarm output
    • Step (not stepless) control – the speed is selected from fixed voltages
    • Heavy weight and large dimensions compared with electronic controllers
    • Indoor use only, operating temperature up to +35 °C
    • Not suitable for EC fans and motors controlled by a frequency inverter

    Safety and installation notes

    • Installation and connection must be carried out by a qualified electrician with the power disconnected.
    • Always connect the protective earth (PE).
    • Check that the motor is suitable for voltage control and that its rated current does not exceed 7.5 A.
    • Before connecting, check the network type: the controller is designed for a 3×230 VAC supply.
    • The device is heavy – fix it to a load-bearing wall or structure using suitable fixings.
    • For indoor use only (-20…+35 °C, non-condensing); leave space for cooling.

    Quick selection guide

    7.5 A
    3×230 VAC
    5 steps
    Sinusoidal voltage
    IP54
    Suitable when you need:
    • manual control of a three-phase fan up to 7.5 A in a 3×230 VAC network;
    • quiet motor operation without electronic hum;
    • an additional 230 VAC output for a damper or indication.
    Check before use:
    • the mains voltage – 3×230 VAC is required;
    • the motor rated current and whether it is voltage-controllable;
    • the installation location (18.17 kg, up to +35 °C).
    Important reminder: STR-3-75L10 is intended only for a 3×230 VAC network and does not control EC fans.

    FAQ

    Is it suitable for a 3×400 VAC network?
    No, for a 400 VAC network choose the STR-4 series.
    Why transformer rather than electronic?
    The output voltage is sinusoidal, so the motor runs quietly even at low speed.
    What voltages does the motor receive?
    0, 80, 110, 140, 170 and 230 VAC – depending on the knob position.
    Can several fans be connected?
    Yes, provided the motors are of the same type and their total current does not exceed 7.5 A.
    What is the L1 output for?
    Unregulated 230 VAC / 2 A output – for a damper actuator or indication, active when the controller is on.

    Transformer three-phase fan motor speed controller | 7.5A | 3x230VAC | surface-mounted | IP54 | Sentera Controls | STR-3-75L10

    Sentera STR-3-75L10 – transformer speed controller for three-phase fans up to 7.5 A, 3×230 VAC, 5 steps (0-80-110-140-170-230 VAC), sinusoidal output voltage, unregulated 230 V output, IP54 metal enclosure.

    Illustrative image may have been created using AI. The appearance of the product may differ slightly from the image shown. Please refer to the technical specification.

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