Dual motor system

A dual motor system comprising:

• a first motor which is a variable speed synchronous motor providing a lower speed range with a variable speed drive, the first motor having a first rotor;
• a second motor which is an asynchronous induction motor providing a higher speed range with a non-variable speed drive, the second motor having a second rotor;
• a common shaft, wherein the first and second motors are coaxially arranged and aligned on a common axis defined by the common shaft and configured to drive the common shaft, with the first and second rotors being fixed to the common shaft;
• and
• a motor control system configured to control the first motor and engage the second motor as needed to control a speed of the common shaft,
• wherein when the higher speed range is required, the motor control system increases a speed of the first motor until a maximum speed of the lower speed range, and then the motor control system engages the second motor to achieve the higher speed range, and when the second motor is engaged to achieve the higher speed range, the motor control system runs both the first and second motors, with the first motor being current limited.

A dual motor system comprising:

• a first motor which is a variable speed synchronous motor providing a lower speed range of up to between two thousand eight hundred and three thousand revolutions per minute with a variable speed drive, the first motor having a first rotor;
• a second motor which is an asynchronous induction motor providing a higher speed range defined by at least two higher speeds over three thousand revolutions per minute with a non-variable speed drive, the second motor having a second rotor;
• a common shaft, wherein the first and second motors are coaxially arranged and aligned on a common axis defined by the common shaft and configured to drive the common shaft, with the first and second rotors being fixed to the common shaft;
• a motor control system configured to control the first motor and engage the second motor as needed to control a speed of the common shaft;
• and
• a transformer coupled with the second motor and including a first tap on a winding of the transformer which is selectable by the motor control system to provide a first higher speed of the at least two higher speeds, and a second tap on the winding of the transformer which is selectable by the motor control system to provide a second higher speed of the at least two higher speeds.

A dual motor system comprising:

• a first motor of a first type including a first stator and a first rotor providing a lower speed range under a first type of control;
• a second motor of a second type including a second stator and a second rotor providing a higher speed range under a second type of control;
• a common shaft, wherein the first and second motors are coaxially arranged and aligned on a common axis defined by the common shaft and configured to drive the common shaft;
• a motor control system configured to control the first motor and engage the second motor as needed to control a speed of the common shaft;
• and
• a transformer coupled with the second motor and including a first tap on a winding of the transformer which is selectable by the motor control system to provide a first higher speed of the higher speed range, and a second tap on the winding of the transformer which is selectable by the motor control system to provide a second higher speed of the higher speed range.