For some years, so-called clutchless, externally triggered, variable compressors have been used . All well-known compressor manufacturers use a great variety of different basic types. Here is a list of the most common types on the market: Denso, with the types 6SEU & 7SEU, Sanden, with the types PXE 13 & PXE 16. However, Delphi/Harrison is also represented via the CVC7 series, the design of which is very similar to the V5 compressor. This generation of compressors is used by almost all vehicle manufacturers (Audi, BMW, Citroen, Seat, VW, Opel). Externally triggered means that the stroke volume of the compressor is determined by a built-in control valve that is triggered by the air-conditioning control unit, depending on a wide variety of system parameters such as outside/desired temperature, high/low pressure, rotational speed, engine load. Clutchless means that the compressor no longer has an electromagnetic clutch. This means that the compressor is permanently driven via the pulley and works even if the air-conditioning system is switched off. However, in relation to this, the power is regulated down to a few percent.