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Fan speed controller 400 V | TK monitoring | remote run-stop | 2,5 A

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Article code STRA4-25L40
GTIN 0.540.100.301.594.0
Intrastat number
Category Advanced AC fan speed control - TK monitoring
Current stock 3 U.
Factory lead time 5 Day(s)

Product description

STRA4 is a 5-step fan speed controller designed for three-phase 400 V motors with thermal contacts. Its maximum combined motor current of 2,5 A.

Fan speed is adjusted using a rotary switch with an OFF position. The motor can be enabled or disabled remotely using digital inputs.

To ensure motor safety, STRA4 incorporates a TK monitoring function. In case of overheating, the TK monitoring function deactivates the motor to prevent damage.
In the event of a power failure, STRA4 features automatic restart. After a power outage, the motor restarts automatically without any manual intervention.

STRA4 includes an alarm output and an unregulated output. The alarm output can trigger external devices to generate alarms. The unregulated output can control external devices to confirm normal operation or activate additional equipment.

Fan speed is regulated by reducing the motor voltage using autotransformers. This technology ensures that the output voltage has a perfect sine shape, guaranteeing silent operation of the motor and minimizing electrical noise.

The enclosure of the STRA4 is designed for surface mounting and has IP54 protection against the ingress of dirt, dust, and moisture.

Additional specifications and description

5-step fan speed controller with extra features
The rotary switch of this fan speed controller has five positions, each corresponding to a different fan speed. The utilized autotransformer technology reduces the fan speed and motor voltage in 5 steps. The available output voltages for the series are 130, 180, 230, 300 and 400 VAC. The series features TK contacts for thermal motor protection and run/stop contacts (NC – closed / NO – open) for external or remote starting and stopping.
Autotransformer technology is very reliable and robust. It generates a motor voltage with a perfect sinusoidal shape. This results in exceptionally quiet motor operation and extended service life. Any remaining electrical noise from the autotransformers is further filtered by the special impregnation coating.
This speed controller is only suitable for 3-phase, voltage-controllable motors. If you are not sure if your motor is voltage controllable, it is best to contact the motor manufacturer.

Connecting the motor
When wiring a three-phase fan motor, specific guidelines need to be followed to ensure correct connections and safe operation. The motor leads are typically labeled U, V, and W for the three phases, while the controller is supplied using the R, S, and T terminals. The motor voltage should match the available power supply voltage. Depending on the motor voltage and power supply, the motor may need to be wired in either a delta (Δ) or wye (Y) configuration, as indicated by the motor nameplate or manufacturer's documentation. Grounding guidelines specified by local electrical codes should also be followed. 

stra4 transformer controller with TK, 3 phaseInputs offer remote control possibilities

Furthermore, the STRA4 series offers more control options thanks to its extra inputs. Via these inputs, the motor can be remotely enabled or disabled. This can be used, for example, to connect a smoke alarm to the input. If a smoke alarm occurs, the motor will be disabled. The smoke alarm input will override the status of the other input. This way, spread of the toxic smoke gases through the ventilation system can be slowed down. Another example is to connect a door contact to control an air curtain. Whenever the door opens, the door contact is triggered. It then activates the air curtain via the input of the controller. The air curtain will run at a fixed speed, set via the rotary switch.

Fans with TK contact can be thermally monitored
This fan speed controller offers the same speed control as the standard STR-4 series, but with some extra options. One of these options is the possibility to monitor thermal motor contacts. TK or thermal contacts monitor the temperature inside the motor windings. Thanks to the TK, if the motor overheats, the motor will be disabled to prevent motor damage and the TK will activate the alarm output. This alarm output can be used to connect an external alarm module, such as a buzzer or a light. If the motor is not equipped with TK contacts, the two TK terminals of the controller must be bridged to simulate a normal motor temperature.

Auto reset after power failure
The STRA4 has an automatic reset feature in the event of a power failure. This feature ensures that when the power is restored after an outage, the connected motor will restart automatically. This is in contrast to standard fan speed controllers where you would typically need to manually turn the rotary switch to the OFF position and then back to the desired speed position to restart the motor after a power failure.
The automatic reset function in the STRA4 series controller can be a convenient and time-saving feature, especially in situations where you want to ensure continuous operation of a motor without human intervention in the event of a power interruption. This can be particularly useful in applications like ventilation systems, where maintaining a constant fan speed is crucial for proper air circulation and control.

Outputs to control external devices
The unregulated output on the STRA4 series controller provides a fixed output voltage of 230 VAC when the motor is enabled. This output is always either ON (230 Volt) or OFF (0 Volt) and cannot be adjusted or regulated. It has a maximum current rating of 2 A.
The purpose of this unregulated output is to allow for the simultaneous operation of other devices or equipment that need to work in coordination with the fan. Some examples of how this output can be used include: indicator lamp or air duct closing valve. You can connect an indicator lamp to this output to provide a visual indication when the fan is running. If you have air ducts with closing valves that need to be opened or closed when the fan is running, you can use this output to control their actuation.

Enclosure for indoor wall mounting
The enclosure is made out of high quality steel. This material is very tough and offers good protection against impacts. It offers IP54 protection against the ingress of dust and water. This fan speed controller can be installed on a wall or panel indoors. However, to guarantee the fan speed controller's efficient cooling and operation:
•    Choose a cool installation location
•    Avoid direct sunlight and high-temperature areas
•    Make sure the high-quality steel enclosure provides adequate protection against impacts, dust, and water
•    Use the controller for indoor installations.

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