Products catalog

Home/Product Catalog/HVAC control solutions for heating and ventilation/HVAC automation/Speed regulators for fans/Transformer speed controllers for fans
  • New item   -246.89€Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40
    New item   -246.89€Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40 1
    New item   -246.89€Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40 2
    New item   -246.89€Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40 3
    New item   -246.89€Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40 4
    New item   -246.89€Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40 5

    Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40

    Code: STR-4-40L40
    Inquire about this item
    Price 440.90 € VAT incl.
    ( 364.38 € VAT excl. )
    687.79 € You save 246.89 €
    Offer is valid until 2026-12-31
    Want another price? Suggest yours!
  • Product description

    Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40

    STR-4-40L40 – Sentera Controls transformer speed controller for three-phase 400 VAC voltage-controllable fan and pump motors up to 4 A. The speed is changed in 5 steps with a knob; the motor receives a sinusoidal voltage.

    Key idea:
    A basic three-phase fan control solution: autotransformer, 5-step switch and unregulated 230 VAC output. No electronics in the motor circuit – quiet, simple, reliable.
    What it is for STR-4-40L40:
    This model is designed for more powerful fans (up to 4 A) – roof or duct fans in warehouses, workshops, halls or a group of fans.
    Max. motor current
    4 A
    Control
    5-position rotary switch
    Power supply
    3×400 VAC + N, 50–60 Hz
    Protection
    IP54, surface mounting

    Operating principle

    The controller is wall-mounted. The 3×400 VAC supply is connected to R, S, T and N, the motor – to U, V, W, and the unregulated 230 VAC output (L1) can supply a damper actuator or indication.

    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 of the L40 version: 0 – 130 – 180 – 230 – 300 – 400 VAC; of the L50 version (14 A model) – 0 – 170 – 220 – 260 – 300 – 400 VAC (the 130 VAC tap is present but not connected). 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-4-40L40?
    Quiet and durable speed control for three-phase fans or pumps without programming – install it, select the step and everything works.

    Technical specifications

    Product type Transformer three-phase fan motor speed controller
    Manufacturer / code Sentera Controls / STR-4-40L40
    Series STR-4 (1.5 / 2.5 / 4 / 6 / 8 / 11 / 14 A)
    Supply voltage 3×400 VAC, 50–60 Hz, with neutral (R, S, T, N)
    Max. motor current 4 A
    Regulated output (U, V, W) 0 – 130 – 180 – 230 – 300 – 400 VAC (positions 0–5), sinusoidal voltage
    Unregulated output (L1) 230 VAC, 2 A, 50–60 Hz (in all 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 355 mm (letter meanings – according to the datasheet drawing)
    Packaging (L × W × H) 440×310×200 mm
    Weight 18.2 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; also suitable for motors that hum with an electronic controller.
    • Unregulated 230 VAC output (2 A) – for a damper actuator, valve or indicator lamp.
    • Blue LED – it is visible that the controller is switched on.

    Where is it used?

    • Three-phase 400 V fans and pumps
    • Production halls, warehouses, workshops
    • Ventilation of agricultural buildings
    • Three-phase roof, duct and axial fans

    On-demand operation

    For the electrician.
    Standard terminals R, S, T, N, U, V, W, L1, PE – quick connection.
    For the ventilation installer.
    The steps are selected on site, no adjustment required.
    For the building owner.
    Simple knob control, quiet operation, long service life.

    Application guide: how it is used in practice

    Typical STR-4-40L40 applications:

    Site What is connected Result Installer's note
    Production hall Three-phase extract fan → U, V, W Speed is selected according to load and season Check that the motor is suitable for voltage control
    Fan with damper Damper actuator 230 VAC → L1 The damper is powered together with the fan L1 load – up to 2 A
    Noise-sensitive environment A motor that hums with an electronic controller Quiet operation at all steps Choose the step according to the required air volume
    Several fans Three-phase motors of the same type in parallel → U, V, W All change speed together Sum of rated currents ≤ 4 A

    How to select the controller current

    Rated current of the motor(s) Recommended model
    up to 1.5 A STR-4-15L40 (1.5 A)
    1.5–2.5 A STR-4-25L40 (2.5 A)
    2.5–4 A STR-4-40L40 (4 A) ← this model
    4–6 A STR-4-60L40 (6 A)
    6–8 A STR-4-80L40 (8 A)
    8–11 A STR-4110L40 (11 A)
    11–14 A STR-4140L50 (14 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 motor with TK contacts – STRS4; with remote on (NO/NC) and alarm – STRA4 or STTA4; for control by a 0-10 VDC signal – STVS4; for two day/night speeds – SC2A4 or ST2R4 with timer; for control panel mounting – ATR-4 autotransformer; for a 3×230 VAC network – STR-3.

    Pros

    • Sinusoidal output voltage – quiet motor
    • 5 steps and OFF position
    • Unregulated 230 VAC output (2 A)
    • Metal IP54 enclosure
    • No programming

    Cons / limitations

    • No TK terminals – for that choose STRS4
    • No remote control and no 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 4 A.
    • Connect the neutral (N) according to the datasheet diagram (supply 3×400 VAC + N).
    • 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

    4 A
    3×400 VAC
    5 steps
    Sinusoidal voltage
    IP54
    Suitable when you need:
    • manual control of a three-phase fan or pump up to 4 A;
    • quiet motor operation without electronic hum;
    • an additional 230 VAC output for a damper.
    Check before use:
    • the motor rated current and whether it is voltage-controllable;
    • whether the motor has TK contacts – if so, choose STRS4;
    • the installation location (18.2 kg, up to +35 °C).
    Important reminder: STR-4-40L40 does not replace a frequency inverter and does not control EC fans.

    FAQ

    What voltages does the motor receive?
    0, 130, 180, 230, 300 and 400 VAC.
    Why transformer?
    Sinusoidal voltage – the motor runs quietly and does not heat up due to harmonics.
    Can several fans be connected?
    Yes, motors of the same type, provided their total current does not exceed 4 A.
    Is there motor overheating protection?
    No, TK terminals are available in the STRS4, STRA4, STTA4 series.
    Is it suitable for a 3×230 VAC network?
    No, the STR-3 series is intended for that.

    Transformer three-phase fan motor speed controller | 4A | 400VAC | surface-mounted | IP54 | Sentera Controls | STR-4-40L40

    Sentera STR-4-40L40 – transformer speed controller for three-phase fans up to 4 A, 3×400 VAC, 5 steps (0-130-180-230-300-400 VAC), sinusoidal output voltage, unregulated 230 V output, IP54.

    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.
  • privacy policy

    Information