Embodiments of a mixing device power system generally include a power control module, an AC motor, and a variable frequency drive, wherein upon application of AC power to the system, electrical power is provided to the power control module which transmits electrical power to the AC motor, whereby rotation of a mixing spindle is initiated. After the spindle has begun rotating, transmission of electrical power from the power control module to the AC motor is ceased, and substantially simultaneously electrical power transmission is commenced from the power control module to the variable frequency drive which transmits electrical power to the AC motor, whereby rotation of the mixing spindle is continued. A method of using the mixing device power system to mix a fluid sample is also provided.