What are 3-speed control switches and how do they operate?

Many motors today are designed to be as flexible as possible when it comes to speed. A three-speed motor has three field windings and a rotor, all in one housing. Each field winding is designed to spin the rotor at a different speed. This enables one motor to be used for a number of different applications. A three-speed motor usually has four wires, the three speed wires and the common wire. Power is supplied to the common wire and any one of the speed wires for a certain speed.

3-speed control switch for three-speed AC motors
With our SMT-1-30-series you can manually control 3-speed AC fans in 3 steps. They are available with or without Off-position. The three positions provide 230 VAC to each of the three outputs. This allows you to adjust the fan speed from low to high in 3 steps. With the version without Off position your fan will always be running at a predetermined low speed. It can never be completely switched off.

The contact ratings are 10 A for resistive loads and 3 A for inductive loads. Several loads can be connected as long as the indicated maximum current is not exceeded. The enclosure allows inset mounting (IP44) or surface mounting (IP54).

The ECA-1-10-AC capacitor regulator controls 3-step ceiling fans with a maximum current of 1 A or a maximum power of 150 W. By changing the position of the knob, the internal capacitance changes. When it increases, the voltage across the capacitor decreases while that across the fan motor increases. Accordingly, the speed of the fan will increase.

3-step control switch for EC motors or damper actuators
Apart from EC motors or damper actuators, the SMT-D-series can also remotely control frequency inverters (FI-E-series) and AC fan speed controllers (EVS or MVS series). The control switch can be placed in the living room while the fan speed controller is located in a technical room or electrical cabinet. They are available with or without Off position and allow inset mounting (IP44) or surface mounting (IP54). The supply voltage is 10 VDC, and depending on the version, the output signal is divided into 3 or 4 (including the Off position) steps. For some applications, it is desirable to adjust the control signal in order to obtain the optimal fan speed.

SMT-D-3P-AL:
- The output signal of positions 1 and 2 can be adjusted in the range of 1 – 10 VDC via internal trimmers.
- The output signal of position 3 always equals the supplied voltage = 10 VDC.

SMT-D-4P-AL:
- Off position = 0 = 0 VDC output
- The output signal of positions 1 and 2 can be adjusted in the range of 1 – 10 VDC via internal trimmers.
- The output signal of position 3 always equals the supplied voltage = 10 VDC.

SMT-D-4P-EM:
- Off position = 0 = 0 VDC output
- The output signal of position 1 can be adjusted in the range of 3 – 7 VDC via an internal trimmer.
- The output signal of position 2 can be adjusted in the range of 5 – 9 VDC via an internal trimmer.
- The output signal of position 3 always equals the supplied voltage = 10 VDC.

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