The overload relay units within a motor control group have the timing function for their motor thermal memories under the control of a central controller in communication with the overload relays. Thus expensive timing components and control of timestamps can be removed from individual overload relays. Further reduction of individual overload relay components can be accomplished by removing the nonvolatile memory function from the individual overload relays and allowing the central controller to perform the nonvolatile memory functions for the overload relays. The motor thermal model function for the overload relays can remain in the overload relays or might be moved to the central controller if communication bandwidth permits.

The purpose of the present invention is to provide an electric motor system such that loss of synchronism of an inverter-driven synchronous motor with no magnetic pole position sensor can be easily detected. In order to achieve the purpose, the present invention pertains to an electric motor equipped with a synchronous motor, an inverter having a power conversion device for driving the synchronous motor, and a load connected to the synchronous motor, and is configured such that loss of synchronism of the synchronous motor is determined on the basis of a direct-current voltage in the power conversion device.

A method of operating an electric induction motor with a variable-speed drive includes determining a voltage level on a DC bus for the drive, and measuring a first magnitude of magnetic flux from a stator of the normally-operating electric motor, determining a normal flux level. The method includes disabling a first output to the drive when the DC bus voltage is less than a first threshold level. The method includes measuring a magnetic flux feedback signal having a phase and second magnitude, estimating a speed of the electric motor, and configuring a second output signal for the drive when the DC bus voltage is greater than a second threshold level. The second output signal matches a signal from the second magnitude and a phase of magnetic flux. The method includes enabling the drive output to restart the electric motor when the magnetic flux is greater than a third threshold value.

The invention relates to the field of alternating current electric machines and is intended for restoring winding insulation to its original parameters. According to the present method of drying the windings of an electric machine, a direct current having a magnitude of 10-60% of the nominal value of the current intensity in the windings is passed through the windings for intervals of 1-10 seconds. The active direct current intervals are alternated with pauses, which differ from said intervals by 0.5-1.5 times. In one embodiment of the invention, for the purpose of passing direct current through the windings, an intentionally small direct voltage is applied to the winding ends and is increased until a predetermined direct current intensity is reached. In another embodiment, the resistance of the insulation is determined during the pauses and once it has reached a given value, current is no longer supplied. The invention provides for the more rapid drying of winding insulation without the risk of damage to the insulation material.

A system for reducing inrush loading when a source power is restored includes a device for switching power that selectively connects a load to the source of power and a circuit for measuring the AC voltage at the source and for determining when the AC voltage is within operating range. Responsive to the AC voltage being within operating range, the system delays for a time period then connects the load to the source of power by way of the device for switching power.

According to at least some embodiments, a method for driving a motor includes, upon a restart of the motor, determining whether the rotor is rotating based on a signal generated from outputs of at most one Hall sensor. The method further includes, if it is determined that the rotor is rotating, determining a plurality of output duty values for driving a plurality of windings of the motor. The method further includes generating a drive signal for driving the motor based on the determined plurality of output duty values.

An electric vehicle control system and a control method, an electric vehicle power-on method, an electric vehicle power-off method, and an electric vehicle charging method are disclosed in this application. The control system includes a domain control unit controlling an electric vehicle, a current sampling unit sampling the current of a power battery and a motor of the electric vehicle and sending sampling signals to the domain control unit, and electrical device, driven by the power battery, sampling the current flowing through it and sending the sampling signals to the domain control unit. The domain control unit, according to the sampling signals sent by the electrical device and the current sampling unit, manages the power battery and controls a motor driver module and the electrical device. The structure of the control system and the control policy are simplified and the power-on and power-off time is shortened.

According to an embodiment, a method for compensating instantaneous power failure includes determining whether an input voltage of a plurality of power cells is less than or equal to a first threshold voltage, decreasing, when the input voltage is less than or equal to the first threshold voltage, an output frequency of the inverter, determining whether a voltage of a direct current (DC) link is greater than or equal to a second threshold voltage, and increasing, when the voltage of the DC link is greater than or equal to the second threshold voltage, the output frequency of the inverter. Overvoltage trip may be prevented at the power restoration time and overcurrent trip caused by increase in the slip frequency may be prevented. Thereby, reliability of a medium inverter may be enhanced, and a continuous operation time increased compared to the conventional cases may be ensured.

When a rotation start position of a rotation shaft 132 is a middle start position 31a (i.e., when rotation of the rotation shaft 132 is stopped in the middle and the rotation is restarted), target rotational speed (relative target rotational speed) is defined using a relative pattern 31 that uses the middle start position 31a as a reference, without using an absolute pattern 33 that is defined using a normal rotation start position 33a as a reference. Upon detecting that a condition that absolute target rotational speed corresponding to an angular position detected by a rotation sensor 134 is greater than the relative target rotational speed is not satisfied, motor control is switched so that the absolute pattern 33 is used.

A system and method for estimating operating characteristics of an induction motor is disclosed. The system includes a motor control device that is electrically connectable between a motor and a power source. The motor control device includes a plurality of switching devices comprising at least one thyristor corresponding to a respective phase of the motor. The motor control device also includes a controller programmed to disconnect the power source from the motor for a predetermined time period following a first plurality of cycles of a mains phase voltage of the power source. The controller is further programmed to measure a back-emf voltage during the predetermined time period, estimate an operating characteristic of the motor from the measured back-emf voltage, and trigger the plurality of switching devices to reconnect the power source to the motor following estimation of the operating characteristic.