Air conditioning and heating system for the Škoda 28T tram for Konya

The air conditioning and heating system for the Škoda 28T tram is designed for cooling, ventilation, heating and conditioning the air supplied to the passenger compartment and for the driver's cabin in the tram.

Four main systems were implemented within the project:

• passenger compartment air conditioning units of the KLMT28S type
• driver’s cabin air conditioning units of the KLMT28K type
• power converters of the NST-4006 type for the KLMT28K unit
• heating units of the KVA-03 type in three versions

For each air conditioning unit, fresh air is supplied via an adjustable damper to the mixing chamber, where it is mixed with recirculation air. From the mixing chamber, air is supplied via a filter, cooler (evaporator) and electric heater to the air ducts of the vehicle. Filters prevent the entry of dirt and dust into the entire air handling unit, as well as clogging of coolers, heaters and fan impellers.

The cooler (evaporator) of air conditioning units is used to reduce the air temperature. It is part of the refrigeration circuit together with the compressor and is filled with R134a refrigerant. The cooling capacity is controlled by changing the speed of the compressors using a frequency converter.

Heating power control is provided by controllers that make it possible to continuously change the voltage on electric heaters using semiconductor converters. The advantage is the possibility of achieving a better curve of the controlled temperature (higher comfort for passengers) and at the same time achieving a significantly smaller number of switching of the heating system contactors. In the passenger compartment, heating with KVA-03 heating units is preferred. It is also ensured that cold air does not flow from the air conditioning units in heating mode to the passengers.

To reduce the relative humidity of the air, the air conditioning unit is equipped with a dehumidification mode. In this mode, it is possible to start the compressor refrigeration circuit together with the electric heater.

The air conditioning and heating system is automatic and works according to the required parameters set by the vehicle driver. Each air conditioning unit contains a control unit. Communication with the host control system of the vehicle takes place via a secured Ethernet line.

The air conditioning units are designed to be mounted on the roof of the vehicle. The top lids of the units are fully walkable. Thanks to the aluminum structure of the container and the integrated power converters, a low specific weight is achieved. The passenger compartment air conditioning unit is equipped with an integrated power converter with galvanic isolation and inverters. Therefore, it can be powered directly from the 600 V or 750 V DC traction network.

Characteristics

• Control via vehicle Ethernet
• Compatible with TST (Tuning and Service Tool)
• Integrated frequency converters
• Continuous speed control of fans and compressor
• Contactless heating system control
• Power supply from overhead line
• Advanced diagnostics, event logger and operational data recorder

Technical parameters of the KLMT28S unit

Technical parameters of the KLMT28K unit

Technical parameters of the NST-4006 power converter

Fotogalerie