Dick Caro reminded control systems engineers that the electronic variable frequency drive (VFD) was an alternative to the control valve as the final control element in liquid flow control applications. Not only is this application less complicated than the more conventional use of a control valve, but it is also widely known to save energy. Some control engineers have known this for many years, but have been reluctant to specify use of the VFD chiefly because they're unfamiliar with it.
