Method of reducing vibrations in an electric motor

A control system for reducing vibrations in an electric motor including a rotor and a stator, the control system comprising:

• processing circuitry, and
• a storage medium comprising computer code, which when executed by the processing circuitry is configured to cause the control system to perform the method including:
• a) determining whether one of an angular rotational speed (ωm) of the rotor and an angular stator frequency (ωl) multiplied by two is within a critical range comprising a mechanical resonance frequency of a motor assembly comprising the electric motor and its load,
• b) i) setting an oscillating incremental torque angular frequency (ωr) of the AVC to the angular rotational speed (ωm) of the rotor if the angular rotational speed (ωm) of the rotor is within the critical range, or
• ii) setting the oscillating incremental torque angular frequency (ωr) to the angular stator frequency (ωl) multiplied by two if the angular stator frequency (ωl) multiplied by two is within the critical range,
• iii) generating an oscillating incremental torque reference (τr) using the AVC with the oscillating incremental torque angular frequency (ωr) set in step b i) or b ii), and
• iv) controlling the electric motor based on a sum of the oscillating incremental torque reference (τr) and an electrical torque reference;
• or
• c) i) deactivating the AVC if the angular rotational speed (ωm) of the rotor and the angular stator frequency (ωl) multiplied by two is outside the critical range, and
• ii) controlling the electric motor based on the electrical torque reference.

A motor system comprising:

• an electric motor,
• a control system for reducing vibrations in an electric motor including a rotor and a stator, the control system comprising:
• having processing circuitry, and
• a storage medium comprising computer code, which when executed by the processing circuitry is configured to cause the control system to perform the method including:
• a) determining whether one of an angular rotational speed (ωm) of the rotor and an angular stator frequency (ωl) multiplied by two is within a critical range comprising a mechanical resonance frequency of a motor assembly comprising the electric motor and its load,
• b) i) setting an oscillating incremental torque angular frequency (ωr) of the AVC to the angular rotational speed (ωm) of the rotor if the angular rotational speed (ωm) of the rotor is within the critical range, or
• ii) setting the oscillating incremental torque angular frequency (ωr) to the angular stator frequency (ωl) multiplied by two if the angular stator frequency (ωl) multiplied by two is within the critical range,
• iii) generating an oscillating incremental torque reference (τr) using the AVC with the oscillating incremental torque angular frequency (ωr) set in step b i) or b ii), and
• iv) controlling the electric motor based on a sum of the oscillating incremental torque reference (τr) and an electrical torque reference;
• or
• c) i) deactivating the AVC if the angular rotational speed (ωm) of the rotor and the angular stator frequency (ωl) multiplied by two is outside the critical range, and
• ii) controlling the electric motor based on the electrical torque reference, and
• configured to control the electric motor.