An apparatus and method for cooling a compressor motor (152) having a motor stator (162) and rotor (166) in a refrigerant system (100). The method cools the rotor and the stator, electromagnetic bearings (160) located within a compressor housing providing refrigerant liquid to the stator internal channels, the channels being in fluid communication with a rotor passageway (172), and a flow-control device (168) controlling refrigerant flow into the stator. A temperature monitoring device (176) in communication with a controller (140) monitors motor temperature. The controller (140) evaluates the motor temperature and adjusts refrigerant flow through the flow control device (168), maintaining the motor (152) within a predetermined temperature range.

Hermetic motor cooling and control

A compressor (22) has a housing assembly (40) with a suction port (24), a discharge port (26), and a motor compartment (60). An electric motor (42) has a stator (62) within the motor compartment and a rotor (64) within the stator. The rotor is mounted for rotation about a rotor axis (500). One or more working impellers (44) are coupled to the rotor to be driven by the rotor in at least a first condition so as to draw fluid in through the suction port and discharge the fluid from the discharge port. An inlet guide vane (IGV) array (174) is between the suction port (24) and the one or more impellers (44). One or more bearing systems (66, 68) support the rotor (64) and/or the one or more impellers (44). One or more main drain passages (120,234 206; 120, 232, 202, 206) are coupled to the bearings to pass fluid along a drain flowpath from the bearings to a location (172) upstream of the impeller and downstream of the IGV array.

Compressor bearing cooling

Nonlinear dynamic simulation and parametric analysis of a rotor-AMB-TDB system experiencing strong base shock excitations

For the unbalance vibration of the rigid rotor system on active magnetic bearings (AMBs) supported high-speed motors in the full rotational speed range, a method based on the polarity switching tracking filter (PSTF) and the disturbance observer (DO) is proposed to achieve vibration suppression. To identify the synchronous unbalance vibration, a positive polarity tracking filter and a negative one are adopted before and after the rigid critical rotational speed range, respectively. The rigid critical rotational speed is in this range whose lower/upper limit is the negative/positive polarity switching frequency. Although the PSTF can effectively reduce the rotor vibration when it rotates at subcritical rotational speed range and supercritical range, the vibration increases evidently and even destabilize the system within the rigid critical rotational speed range. It means that the PSTF cannot suppress the rotor unbalance vibration in the full rotational speed range. However, this vibration during the rigid critical rotational speed range can be considered as a kind of disturbance and the DO is adopted to observe it, then the vibration identified is compensated in the control current to reduce the rotor unbalance vibration in the rigid critical rotational speed range. Therefore, the method based on the PSTF and the DO can suppress the unbalance vibration in the full rotational speed range. Finally, simulation and experiment results demonstrate that the method proposed can effectively suppresses the synchronous unbalance vibration of the AMBs-rigid rotor system in the full rotational speed range.

Vibration Suppression for Magnetically Levitated High-Speed Motors Based on Polarity Switching Tracking Filter and Disturbance Observer

In active magnetic bearings (AMBs) supported rigid rotor systems, the unbalance compensation strategy based on a notch filter was often used to suppress the synchronous unbalance vibration when the rotor operates in the steady-state rotational speed. Whereas the rotor operates in a rotational-speed range including the critical rotational speeds, conventional notch filters should be improved to suppress the unbalance vibration. In most cases, improving the structure of the notch filter, such as a cross-feedback notch filter, phase-shift notch filter, adding the polarity switch or two-stage switch, was considered to make the notch filter work in the rotational-speed range. However, the improved notch filter may affect the stability of the AMBs rotor systems and result in large vibrations when the polarity switch or two-stage switch shifts. To avoid the shortcomings of these methods, a method using a variable angle compensation algorithm was proposed to suppress the synchronous unbalance vibration in finite iterative seeking processes, directly realizing unbalance compensation according to real-time rotor position. Finally, the effectiveness of the method proposed is verified by simulation and experiment results.

Synchronous Vibration Control for Magnetically Suspended Rotor System Using a Variable Angle Compensation Algorithm

A cooling system (10) is provided for a motor (50) powering a compressor (32) in a vapor compression system (14). The cooling system (10) including a housing (114) and a cavity (126) within the housing (114). A first fluid circuit (140) has a first connection (112) to receive a refrigerant into the cavity (126), and a second connection (154) to deliver refrigerant from the cavity (126) to a heat exchanger for a heat transfer relationship with a heat-generating component (120).

Motor cooling applications

Qualification shock testing has been completed for a new chilled water plant developed for the US Navy. The variable speed compressor at the heart of the chiller system includes a direct drive, high-speed permanent magnet (PM) motor, PM bias active magnetic bearings, and a backup bearing system. For MIL-S-901D shock certification, the chiller was mounted on a Navy floating shock platform (barge) and subjected to a standard sequence of four different shock impacts generated from high explosive charges from varying angles and standoff distances. The chiller was fully operational during three blasts and in standby mode for the fourth blast. In the standby mode, the shaft is de levitated and stationary on the backup bearings and the chiller secured. The backup bearing system of the motor absorbed the response to the shock impacts and the magnetic bearings subsequently recovered levitation as designed. The shock testing was simulated using a transient, nonlinear rotordynamic analysis including the magnetic bearing control and saturation features, backup bearings with resilient mounts and associated clearances, and structural dynamic models of the rotor and housing. Compressor/motor housing acceleration measured during the testing was used as the driving input into the simulation. Some rotor position data recorded during shock testing, the simulation approach and comparisons are reported and discussed.

Floating Shock Platform Testing of a Magnetic Bearing Supported Chiller Compressor: Measurements and Simulation Results

External vibration testing was performed on a semihermetic, direct drive compressor on magnetic bearings intended for U.S. Navy Shipboard use. The compressor was placed on a U.S. Navy MIL-STD-167 shaker platform and driven at sinusoidal frequencies from 4 to 33 Hz at graduated displacements equal to a maximum of 1.5 Gs. During the machine design phase, a linear forced response analysis of the coupled rotordynamic system model of the rotor, housing, and magnetic bearings was performed to predict rotor/housing displacements and actuator loads. The results were used to guide bearing sizing and control algorithm design. The measured rotor motion and actuator currents correlated well with predictions at all tested frequencies, amplitudes, and orientations. Analysis methodology, test results, and comparisons are reported here.

Test Results and Analytical Predictions for MIL-STD-167 Vibration Testing of a Direct Drive Compressor Supported on Magnetic Bearings

External vibration testing was performed on a semi-hermetic, direct drive compressor on magnetic bearings intended for US Navy Shipboard use. The compressor was placed on a US Navy MIL-STD-167 shaker platform and driven at sinusoidal frequencies from 4 to 33 Hz at graduated displacements equal to a maximum of 1.5Gs. During the machine design phase, a linear forced response analysis of the coupled rotordynamic system model of the rotor, housing and magnetic bearings was performed to predict rotor/housing displacements and actuator loads. The results were used to guide bearing sizing and control algorithm design. The measured rotor motion and actuator currents correlated well with predictions at all tested frequencies, amplitudes and orientations. Analysis methodology, test results, and comparisons are reported here.© 2014 ASME

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Test Results and Analytical Predictions for MIL-STD-167 Vibration Testing of a Direct Drive Compressor Supported on AMB

A vapor compression system including a motor having a housing and a shaft having an axis, the shaft urgable into rotational movement by the motor for powering a system component. A primary bearing and a secondary bearing are positioned in the housing for rotatably supporting the shaft, the primary bearing rotatably supporting the shaft during normal system operation. A first bearing stop and a second bearing stop are positioned on opposite sides of the secondary bearing for transmitting axial forces generated along the shaft for reaction by the motor housing during abnormal system operation. At least a portion of corresponding surfaces of each of the first bearing stop and the second bearing stop facing the secondary bearing have a protective overlying layer of material applied thereto.

Koman B. Nambiar

Papers

Motor cooling applications

Floating Shock Platform Testing of a Magnetic Bearing Supported Chiller Compressor: Measurements and Simulation Results

Test Results and Analytical Predictions for MIL-STD-167 Vibration Testing of a Direct Drive Compressor Supported on Magnetic Bearings

Test Results and Analytical Predictions for MIL-STD-167 Vibration Testing of a Direct Drive Compressor Supported on AMB

Vapor compression system and method of extending service life of same