Methods and control apparatus for operating a three-phase electric motor are described, in which the motor windings are switched between Star and Delta connections depending on torque requirements, and in which the motor windings are switched to a braking mode when braking torque is required. The electromagnetic torque of the motor is monitored, and a command to switch from Star to Delta is given when the electromagnetic torque rises to reach or exceed a threshold. A command to switch from Delta to Star is given when the electromagnetic torque falls to reach a second threshold. The invention discloses a method of determining instantaneous values for the electromagnetic torque of the motor based on measurements of phase current and phase voltage at particular instants in the voltage cycle. The application further discloses a method of timing the switching operation between Star and Delta configurations, or switching from Star or Delta configuration to a dynamic braking mode, to minimise inrush currents by monitoring the vector relationship between the EMF and the supply voltage and performing switching operations in each motor phase when EMF vector is aligned with the supply voltage vector. The application further discloses switching from Star to Delta or Delta to Star when the torque produced by the motor is substantially equal to the torque requirement of the load to maximise efficiency.

Methods and control apparatus for operating a three-phase electric motor are described, in which the motor windings are switched between Star and Delta connections depending on torque requirements, and in which the motor windings are switched to a braking mode when braking torque is required. The electromagnetic torque of the motor is monitored, and a command to switch from Star to Delta is given when the electromagnetic torque rises to reach or exceed a threshold. A command to switch from Delta to Star is given when the electromagnetic torque falls to reach a second threshold. The invention discloses a method of determining instantaneous values for the electromagnetic torque of the motor based on measurements of phase current and phase voltage at particular instants in the voltage cycle. The application further discloses a method of timing the switching operation between Star and Delta configurations, or switching from Star or Delta configuration to a dynamic braking mode, to minimise inrush currents by monitoring the vector relationship between the EMF and the supply voltage and performing switching operations in each motor phase when EMF vector is aligned with the supply voltage vector. The application further discloses switching from Star to Delta or Delta to Star when the torque produced by the motor is substantially equal to the torque requirement of the load to maximise efficiency.

Various embodiments include determining an alternating current (AC) voltage and frequency of a supply voltage coupled to a circuit input. The circuit includes a soft starter circuit that is coupled between the circuit input and a first side of an AC motor. A stator winding configuration of the AC motor is determined. A control transformer is configured in response to the AC voltage and frequency, wherein the control transformer is coupled to the circuit input. A jumper device is configured on a second side of the AC motor in response to the stator winding configuration of the AC motor.

Various embodiments include determining an alternating current (AC) voltage and frequency of a supply voltage coupled to a circuit input. The circuit includes a soft starter circuit that is coupled between the circuit input and a first side of an AC motor. A stator winding configuration of the AC motor is determined. A control transformer is configured in response to the AC voltage and frequency, wherein the control transformer is coupled to the circuit input. A jumper device is configured on a second side of the AC motor in response to the stator winding configuration of the AC motor.

One embodiment describes a method that includes determining, using a control circuitry, temperature of a switching device before a make operation by applying a measurement current to an operating coil of the switching device, wherein the measurement current is insufficient to make the switching device; and determining voltage at the operating coil when the measurement current is applied, in which the voltage at the operating coil is directly related to the temperature. The method further includes determining, using the control circuitry, when to apply a pull-in current to the operating coil to close the switching device based at least in part on the voltage at the operating coil, such that the switching device makes at a desired time.

One embodiment describes a tangible, non-transitory, computer-readable medium storing instructions executable by a processor of an operating coil driver circuitry. The instructions include instructions to instruct a switch to supply a specific current to an operating coil of a switching device using a pulse-width modulated signal; determine duty cycle of the pulse-width modulated signal; and determine wellness of the switching device based at least in part on the duty cycle of the pulse-width module signal.

A vacuum pump drive comprising at least one electric motor which is connected to the rotor of a vacuum pump via a drive shaft, a frequency converter which is electrically connected to the motor and which supplies a motor input voltage to the motor, and a switchover device with at least one electric switch. The switchover device is designed to connect the motor windings in a star or delta shape depending on the switching position of the switch in order to change the motor characteristic curve. The vacuum pump drive also comprises a measuring device with sensors for detecting physical operating variables of the vacuum pump and a controller which is electrically or optically connected to the switchover device and the measuring device and which is designed to actuate the at least one switch on the basis of the measured value of the operating variable of the vacuum pump in order to produce the star-delta switchover.

A system (10) applied in switch tube for suppressing conducted EMI and a domestic appliance are provided, and the system (10) includes a conduction EMI suppression circuit, an inductive load (1, 71, 81) and at least one switch tube (2, 72, 82). The conducted EMI suppression circuit includes one inductor (3, 73, 83, 123) and an RC circuit (4, 74, 84, 124). The inductor (3, 73, 83, 123) and each switch tube (2, 72, 82) are connected in series. The inductive load (1, 71, 82) and each switch tube (2, 72, 82) are connected. The inductor (3, 73, 83, 123) are connected in series with each switch tube (2, 72, 82), and further connected in parallel with the RC circuit (4. 74, 84, 124). The conduction EMI suppression circuit is configured to suppress conducted EMI generated by each switch tube (2, 72, 82) being turned off.

One embodiment describes a method that includes in a first switching operation of an electrical power switching system including three separately controllable single pole, single current-carrying path switching devices that provide three-phase power to a load, and control circuitry coupled to the switching devices to control closing and opening of the current-carrying paths, commanding at least one of the switching devices to open or close in advance of at least one other of the switching devices based upon a current zero-crossing or a predicted current zero-crossing of input three-phase power; and in subsequent switching operations alternating which of the three switching devices is closed or opened in advance of another of the switching devices.

One embodiment describes a method that includes in a first switching operation of an electrical power switching system including three separately controllable single pole, single current-carrying path switching devices that provide three-phase power to a load, and control circuitry coupled to the switching devices to control closing and opening of the current-carrying paths, commanding at least one of the switching devices to open or close in advance of at least one other of the switching devices based upon a current zero-crossing or a predicted current zero-crossing of input three-phase power; and in subsequent switching operations alternating which of the three switching devices is closed or opened in advance of another of the switching devices.