ABSTRACT
The urbanization is expanding. By the end of the century, 50% of the world’s population will be urban. Cities and their infrastructure grow rapidly. This also applies to tunnels and metros. The important aspect in such projects is ventilation. Ventilation ensures wellbeing of tunnel users in normal situations and provides safety in case of emergencies.
Active ventilation is based on air movement via a fan wheel run by an electrical motor. To control the air flowrate, direction and pressure, variable speed drives are used. They are a vital part of ventilation as they help ensure process efficiency, reliability and tunnel safety.
Ventilation typically consumes a lot of energy used by a tunnel, so drives are often employed to increase tunnel energy efficiency and decrease operating expenses. Drives adjust the fan motor speed based on the vehicle fumes concentration, therefore saving energy.
In case of a fire, drives make smoke control flexible. They regulate fan speed and rotation direction to ensure smoke stratification and combat backlayering for safe evacuation. Fire in a tunnel implies fast response from ventilation and smoke extraction systems. Drives provide prompt fan start, stop, rotation direction change which are the key requirements in tunnel ventilation.
Active front end drives go beyond fan speed control. They ensure power quality eliminating disturbances in the network, for reliable ventilation. It is important for long tunnels with weak power supply and long cabling. This type of drives also contributes to the tunnel sustainability, as power quality affects power network equipment sizing. The drives allow to decrease e.g. electrical generator size by 50% or transformer size by 20% – a huge input to the carbon footprint reduction.
