Fan speed control transformers

The ability to use several speed modes of the electric motor allows the most efficient and comfortable operation of any ventilation system, fan coil units, dehumidifiers, air conditioners, etc. Maximum speed is not always required, and their reduction by only a few percent leads to a significant reduction

• noise level,
  
• electrical and mechanical heating of the system (that is, energy losses),
  
• wear - both the motor and the impeller.
  

Despite the advances in semiconductor technology, the most reliable device for changing the supply voltage (through which speed control is carried out) remains the good old transformer. It does not contain moving parts, active (or any) electronic components and, if sealed (monolithic insulation), can last for centuries. The efficiency of such regulators is 95% or more, which is achievable only in the most modern and expensive electronic ones. Since the isolation and grounding of motors and housings in such systems provides reliable protection against the phase voltage of the network, in regulating transformers, for economic reasons, an autotransformer winding connection scheme is used - without galvanic isolation of primary and secondary. For effective fan control, five voltage levels (windings with five taps) are enough.