This electric compressor includes a compressor which rotates to compress a fluid, a motor which rotatably drives the compressor, and a control unit which controls current supply to the motor using first and second components. An allowable current for first and second components exposed to the same temperature is set to be smaller in the second component than in the first component. The second component is disposed at a place in which cooling capability is greater than that of the first component so that allowable power of the second component at rated use is greater than allowable power of the first component. This electric compressor includes a temperature sensor which detects the temperature of the first component and a calculation unit which outputs an alarm signal when the detected temperature and a current flowing in the first component satisfy a predetermined condition.

The present disclosure describes a load/unload control method for a compressor system with a rotating compressor connected to a pressure vessel. In the method, the present operating state can be monitored on the basis of a monitored/estimated electrical quantity of the compressor system. The method comprises an identification phase and an operational phase. In the identification phase, the compressor is operated at a constant rotational speed to generate two known pressures to the pressure vessel. At least one electrical quantity is monitored, and values of the electrical quantity corresponding to the pressure limits are stored. In the operational phase, reaching of a pressure limit may then be detected by comparing the present value of the monitored electrical quantity to the stored values.

An in-vehicle motor-driven compressor includes a temperature rise estimator configured to estimate a temperature rise of the diode based on an expected reverse current, an on-voltage of the diode, and a heat resistance of the diode. The in-vehicle motor-driven compressor further includes a rotation speed controller configured to set a rotation speed limit of the electric motor, based on the estimated temperature rise of the diode so that a temperature of the diode does not exceed a junction temperature of the diode even when the electric motor is stopped and the reverse current flows through the diode, and limit a rotation speed of the electric motor to lower than or equal to the rotation speed limit.

An air compressor (10) includes an air pump (34) with a pump inlet (34a) for receiving air to be pressurized and a pump outlet (34b). An air tank (14) includes a tank inlet (14a) coupled with the pump outlet (34b) for receiving pressurized air from the air pump (34), and a tank outlet (14b) for directing pressurized air from a tank outlet (14b) to at least one pneumatic device (24). A brushless DC motor (36) includes a rotatable output (36a) coupled with the air pump (34) for operating the air pump (34) to pressurize air. A control (42) is electrically coupled to the brushless DC motor (36). The control (42) changes the level of electric current drawn by the brushless DC motor (36) to thereby change the rate of rotation of the rotatable output (36a) and/or the pump performance level.

An electrically operated device (10) includes an electric motor (36) with an electrical cord set (30). The cord set (30) includes an electrical connecting plug (80) for coupling with an AC electrical outlet. The device (10) further includes a detector (46). A control (42) is electrically coupled to the motor (36) and electrically coupled to the detector (46) for controlling the level of electric current drawn by the electric motor (36) from the AC electrical outlet. The detector (46) detects whether the electrical connecting plug (80) is connected to a 15 Amp electric receptacle or to a 20 Amp electric receptacle and, in response, the control (42) establishes the electric profile of the electric motor (36) to correspond to the 15 Amp electric receptacle or to the 20 Amp electric receptacle.

When the magnitude of a motor current Iu is smaller than a threshold value at a timing when a polarity of the motor current Iu is expected to be reversed after the elapse of one control cycle, a control device sets a correction amount of a width of a pulse generated by PWM control at a correction amount +. When the magnitude of the motor current is greater than the threshold value at the timing, the control device sets the correction amount of the width of the pulse generated by the PWM control at zero or a value smaller than the correction amount +. As a result, an error of a dead time period in inverter control can be reduced.

A control method is used with a control system to control a screw pump. The control system includes an electric motor and a motor drive. The control method includes following steps. Firstly, a DC bus voltage is monitored. If the DC bus voltage is smaller than a first threshold value, a potential energy stored in the pump screw and released by a backspin action is converted into a regenerative electrical energy so as to maintain a normal operation of the motor drive. Then, the motor drive drives the electric motor to control the backspin action of the screw pump according to a backspin torque limit strategy. If the electrical power from the power source is not restored and the level of a reverse regenerative torque is smaller than a preset torque value, the backspin action of the screw pump is stopped freely.

This electric compressor includes a compressor which rotates around an axis to compress a fluid, a motor which rotatably drives the compressor around the axis, and a control unit having a first component and a second component and controlling current supply to the motor during driving using the first component and the second component. An allowable current when the first component and the second component are exposed to the same temperature is set to be smaller in the second component than in the first component. The second component is disposed at a place in which cooling capability is greater than that of the first component so that allowable power of the second component at rated use is set to be greater than an allowable power of the first component. This electric compressor includes a temperature sensor which detects the temperature of the first component and a calculation unit which outputs an alarm signal when the temperature detected by the temperature sensor and a current flowing in the first component satisfy a predetermined condition.

An apparatus is provided for controlling a vehicle air compressor having compressor oil to track water content in the compressor oil due to condensation during operation of the compressor over a plurality of time intervals. The apparatus comprises a data storage unit arranged to store a condensation control algorithm. The apparatus also comprises a processing unit arranged to apply the condensation control algorithm to calculate a net rate of condensation of water in the compressor oil during operation of the compressor over a first time interval of the plurality of time intervals, and maintain a running total of how much water is in the compressor oil at any given time over the first time interval to enable the compressor to operate in different modes of operation based upon the running total of how much water is in the compressor oil.

When the magnitude of a motor current Iu is smaller than a threshold value at a timing when a polarity of the motor current Iu is expected to be reversed after the elapse of one control cycle, a control device sets a correction amount of a width of a pulse generated by PWM control at a correction amount +. When the magnitude of the motor current is greater than the threshold value at the timing, the control device sets the correction amount of the width of the pulse generated by the PWM control at zero or a value smaller than the correction amount +. As a result, an error of a dead time period in inverter control can be reduced.