A variable-frequency drive (VFD) (also termed adjustable-frequency drive, variable-speed drive, AC drive, micro drive or inverter drive) is a type of adjustable-speed drive used in electro-mechanical drive systems to control AC motor speed and torque by varying motor input frequency and voltage.ariable-frequency drives are also categorized by the following load torque and power characteristics: 1  Variable torque, such as in centrifugal fan, pump, and blower applications. 2  Constant torque, such as in conveyor and positive-displacement pump applications.
For example, the UK is a unitary state (for the most part) whereas the US is a federation. A parliamentary form of government simply means that the executive branch/ministers/cabinet are part of the legislative body. Both unitary and federal states can have parliaments. For example, India is a federation with a parliamentary system where as the UK is a unitary state with a parliamentary system. m200220232
A parliamentary system, sometimes called a âcabinet governmentâ may also be a constitutional monarchy. (see the module âConstitutional Monarchies.â) A constitutional monarchy retains the king or queen in the role of head of state, but their power is almost exclusively ceremonial.xamples of parliamentary systems, other than the countries of the United Kingdom, include Canada, Australia, the Scandinavian countries, Germany, Spain and Italy. France and Finland are âhybridâ systems of government, that is they combine features of both the presidential and parliamentary models.