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  • New item   -214.63€Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40
    New item   -214.63€Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40 1
    New item   -214.63€Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40 2
    New item   -214.63€Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40 3
    New item   -214.63€Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40 4

    Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40

    Code: STRA4-25L40
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  • Product description

    Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40

    STRA4-25L40 – Sentera Controls transformer speed controller for three-phase 400 VAC motors up to 2.5 A with TK terminals, NO/NC remote on/off contacts and a 230 VAC alarm output. 5 steps, sinusoidal output voltage.

    Key idea:
    A controller for an automated site: the fan is switched on or off by a thermostat, timer, fire or BMS system via an NO or NC contact, the motor is protected by the TK circuit, and a fault is reported via a 230 VAC alarm signal.
    What it is for STRA4-25L40:
    This model is intended for medium-power fans (up to 2.5 A) – duct fans in offices, classrooms, retail premises or 2–3 smaller fans together.
    Max. motor current
    2.5 A
    Remote control
    NO / NC contacts
    Protection and alarm
    TK, alarm 230 VAC / 1 A
    Supply / protection
    3×400 VAC + N; IP54

    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, the thermal contacts – to TK, an external switch-on signal – to the NO or NC terminals, the alarm indication – to AL and N.

    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.

    The speed is selected with the knob, while switching on / off can be controlled by an external device: a normally open (NO) or normally closed (NC) dry contact. When the motor thermal protection trips, a 230 VAC (up to 1 A) signal appears at the alarm output for a lamp, siren or BMS input. 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 STRA4-25L40?
    One enclosure combines quiet stepped speed control, motor TK protection, remote on via a thermostat or automation, and an alarm output, so no additional relays or contactors are needed.

    Technical specifications

    Product type Transformer three-phase fan motor speed controller with remote on
    Manufacturer / code Sentera Controls / STRA4-25L40
    Series STRA4 (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 2.5 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
    Alarm output (AL, N) 230 VAC, 1 A
    Motor protection TK terminals for motor thermal contacts
    Remote on / off NO (normally open) and NC (normally closed) contact inputs
    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 325 / C 185 / D 255 / E 255 mm (letter meanings – according to the datasheet drawing)
    Packaging (L × W × H) 340×310×210 mm
    Weight 12.59 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

    • NO / NC inputs – the fan is switched on by a thermostat, timer, motion detector or BMS.
    • TK terminals – connection of motor thermal contacts – protection against overheating.
    • Alarm output 230 VAC / 1 A – fault signal for a lamp, siren or automation system.
    • 5 speed steps – the operating speed is set with the knob.
    • Sinusoidal output voltage – quiet motor operation.
    • Unregulated 230 VAC output (2 A) – for a damper actuator or valve.

    Where is it used?

    • Automated ventilation systems with a thermostat or timer
    • Production and storage buildings
    • Sites where a fault signal to the operator is required
    • Ventilation of agricultural buildings

    On-demand operation

    For the electrician.
    TK, alarm and remote control circuits are connected directly to the controller terminals.
    For the automation integrator.
    NO / NC inputs and a 230 VAC alarm allow the controller to be linked to a BMS, thermostat or fire system.
    For the building owner.
    Ventilation switches on when needed, and faults are reported immediately.

    Application guide: how it is used in practice

    Typical STRA4-25L40 applications:

    Site What is connected Result Installer's note
    Warehouse, workshops Thermostat contact → NO input The fan switches on when the temperature rises Select the operating speed with the knob
    Site with a fire system Fire system NC contact → NC input If the circuit is broken, the fan is switched off Coordinate the NC circuit logic with the design
    Control room, BMS AL, N → signal lamp or BMS input Motor overheating is signalled immediately Alarm output load – up to 1 A
    Fan with thermal contacts Motor TK → TK terminals The motor is protected against overheating Connect the TK circuit according to the diagram in the manual
    Fan with damper Damper actuator 230 VAC → L1 The damper opens together with the fan L1 load – up to 2 A

    How to select the controller current

    Rated current of the motor(s) Recommended model
    up to 1.5 A STRA4-15L40 (1.5 A)
    1.5–2.5 A STRA4-25L40 (2.5 A) ← this model
    2.5–4 A STRA4-40L40 (4 A)
    4–6 A STRA4-60L40 (6 A)
    6–8 A STRA4-80L40 (8 A)
    8–11 A STRA4110L40 (11 A)
    11–14 A STRA4140L50 (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 simpler control – STR-4 or STRS4 (with TK); with thermal protection setting – STTA4; for control by a 0-10 VDC signal – STVS4; for two speeds – SC2A4 or ST2R4 with timer.

    Pros

    • NO / NC remote control inputs
    • TK terminals for motor protection
    • Alarm output 230 VAC / 1 A
    • Sinusoidal output voltage
    • Unregulated 230 VAC output (2 A)
    • Metal IP54 enclosure

    Cons / limitations

    • Speed is set only with the knob – there is no analogue 0-10 VDC input (STVS4 is for that)
    • 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 2.5 A.
    • The supply requires a neutral (N).
    • Connect only dry (potential-free) contacts to the NO / NC inputs according to the diagram in the manual.
    • 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

    2.5 A
    3×400 VAC
    TK
    NO/NC
    Alarm 230 VAC
    IP54
    Suitable when you need:
    • a three-phase fan up to 2.5 A switched on by a thermostat, timer or BMS;
    • sites where a fault signal is needed;
    • motors with thermal contacts.
    Check before use:
    • the motor rated current and whether it is voltage-controllable;
    • the external control contact type (NO or NC);
    • the installation location (12.59 kg, up to +35 °C).
    Important reminder: STRA4-25L40 changes speed in steps via the knob; the remote contact controls on/off only.

    FAQ

    What does NO / NC mean?
    NO – normally open contact (switches on when closed), NC – normally closed (switches off when opened). A thermostat, timer or BMS relay can be used.
    What is the alarm output for?
    A 230 VAC (up to 1 A) signal appears there – for a lamp, siren or automation.
    Can the speed be changed remotely?
    No, the speed is selected with the knob; the STVS4 series is intended for analogue control.
    What voltages does the motor receive?
    0, 130, 180, 230, 300 and 400 VAC.
    How does it differ from STRS4?
    STRA4 additionally has NO / NC remote control inputs and an alarm output.

    Transformer three-phase fan motor speed controller with remote on/off | TK | NO/NC | 2.5A | 400VAC | surface-mounted | IP54 | Sentera Controls | STRA4-25L40

    Sentera STRA4-25L40 – transformer speed controller for three-phase fans up to 2.5 A, 3×400 VAC, TK terminals, NO/NC remote on, alarm output 230 VAC, 5 steps, sinusoidal voltage, 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.

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