Mixing device power system and method

A method of for initiating and controlling the rotation of a mixer spindle, comprising:

• providing a mixer;
• wherein said mixer comprises:
• a start actuator;
• a power control module;
• an AC motor;
• a VFD;
• and
• one or more spindles;
• wherein;
• said power control module is electrically connectable to an AC power source;
• said power control module is alternatively electrically connected to one of said AC motor and said VFD;
• said VFD is electrically connected to said AC motor;
• when said power control module is electrically connected to said AC power source, actuation of said start actuator commences the flow of electrical power from said AC power source to said power control module;
• upon receipt of electrical power from said AC power source, said power control module, which is initially electrically connected to said AC motor but not to said VFD, transmits electrical power to said AC motor, whereby said AC motor operates to initiate rotation of at least one said spindle;
• and
• after said rotation of said at least one said spindle is initiated, said power control module is electrically disconnected from said AC motor and is electrically connected to said VFD, whereupon said power control module switches from electrical power transmission to said AC motor to electrical power transmission to said VFD, whereupon electrical power is transmitted from said VFD to said AC motor to continue said rotation of said at least one said spindle;
• electrically connecting said power control module to said AC power source;
• providing a vessel containing a fluid sample such that one said spindle is at least partially disposed within said fluid sample;
• actuating said start actuator, whereby electrical power is transmitted from said power control module to said AC motor and said spindle at least partially disposed within said fluid sample begins rotating;
• and
• ceasing electrical power transmission from said power control module to said AC motor and substantially simultaneously commencing electrical power transmission from said power control module to said VFD, whereby electrical power is transmitted from said VFD to said AC motor and said spindle at least partially disposed within said fluid sample continues rotating.