A circuit interrupter for protecting a protected circuit includes separable contacts, an operating mechanism structured to trip open the separable contacts, a current sensor structured to sense a current flowing through the protected circuit, a temperature sensor structured to sense a temperature of the protected circuit proximate the current sensor, and a processor configured to select a trip time based on the sensed current, to adjust the selected trip time based on the sensed temperature, and to cause the operating mechanism to trip open the separable contacts when the adjusted selected trip time is reached.

A hardware-based detection system includes, among other things, a signal-generating circuit for generating a signal which is functionally related to current in a motor winding, a reference current, and a duration of time. The system may also include a comparator circuit for comparing the generated signal to a reference signal, and for thereby detecting an over-temperature condition in the motor winding. If desired, a compensating circuit may be used to generate a variable reference signal as a function of ambient temperature. A method of operating a detection system is also disclosed. If desired, the detection system may be completely implemented in hardware using an uncomplicated analog circuit architecture.

A motor drive apparatus includes a control assembly that controls driving of a motor. The control assembly includes a controller that outputs a drive signal instructing a drive amount of the motor, a drive that supplies electric current, supplied from an external power supply, to the motor based on the drive signal output from the controller, a current detector that detects electric current flowing through the drive unit, and a first temperature detector that detects temperature of the drive unit. The control assembly calculates a heat storage amount stored in the control assembly at a predetermined cycle, and when the calculated heat storage amount is larger than a predetermined threshold, the control assembly outputs the drive signal that instructs a drive amount smaller than the drive amount at the time of calculation.

A method of generating a gate drive signal for driving a control terminal of a power switch includes detecting a system input signal; determining a signal pulse of the system input signal being a first signal pulse following a power up event, or following an idle period, or following removal of a fault condition; and in response, generating a soft gate drive signal to drive the control terminal of the power switch to softly turn on the power switch. In another embodiment, the method includes determining a duration of the on period of the system input signal exceeding a maximum on duration and in response, disabling the gate drive signal to turn off the power switch; and determining a deassertion transition of the system input signal and in response, blocking the system input signal from the gate drive signal for a minimum off duration.

A method of generating a gate drive signal for driving a control terminal of a power switch includes detecting a system input signal; determining a signal pulse of the system input signal being a first signal pulse following a power up event, or following an idle period, or following removal of a fault condition; and in response, generating a soft gate drive signal to drive the control terminal of the power switch to softly turn on the power switch. In another embodiment, the method includes determining a duration of the on period of the system input signal exceeding a maximum on duration and in response, disabling the gate drive signal to turn off the power switch; and determining a deassertion transition of the system input signal and in response, blocking the system input signal from the gate drive signal for a minimum off duration.

In a method for monitoring a winding temperature of a winding of an electric machine powered by a converter, a heating power applied to the winding of the electric machine is determined and evaluated using a thermal model. A relative increase in a resistance of the winding, when the winding heats up, is determined from the heating power in comparison with a standard reference value for 20 C. winding temperature. The winding temperature is calculated from the relative increase in the resistance, and a warning signal and/or a switch-off signal is generated when a critical winding temperature value is exceeded.

In a method for monitoring a winding temperature of a winding of an electric machine powered by a converter, a heating power applied to the winding of the electric machine is determined and evaluated using a thermal model. A relative increase in a resistance of the winding, when the winding heats up, is determined from the heating power in comparison with a standard reference value for 20 C. winding temperature. The winding temperature is calculated from the relative increase in the resistance, and a warning signal and/or a switch-off signal is generated when a critical winding temperature value is exceeded.

A control device, such as a smart thermostat, employs solid state relays as switches to activate and deactivate systems controlled by the device. Current flows through at least some of the solid state relays are monitored to determine the bulk heating produced in the solid state relays, and their associated circuitry and printed circuit board traces, and this determined amount of bulk heat is added to other determined amounts of bulk heat and is used to compensate the reading provided by temperature sensors within the control device which have been affected by the bulk heat. Further, by measuring the current flow through the power buses to one or more of the solid state relays of the control device, potentially damaging over current conditions can be distinguished from permissible transient over-current conditions and the control device can deactivate any solid state relays which would be damaged while allowing solid state relays which are experiencing allowable transients to remain operating. In the case of a severe over current condition, a current monitoring device can issue a fault signal, triggering an interrupt condition which will cause a processor in the controller to shut down the affected solid state relays very quickly.

A control device, such as a smart thermostat, employs solid state relays as switches to activate and deactivate systems controlled by the device. Current flows through at least some of the solid state relays are monitored to determine the bulk heating produced in the solid state relays, and their associated circuitry and printed circuit board traces, and this determined amount of bulk heat is added to other determined amounts of bulk heat and is used to compensate the reading provided by temperature sensors within the control device which have been affected by the bulk heat. Further, by measuring the current flow through the power buses to one or more of the solid state relays of the control device, potentially damaging over current conditions can be distinguished from permissible transient over-current conditions and the control device can deactivate any solid state relays which would be damaged while allowing solid state relays which are experiencing allowable transients to remain operating. In the case of a severe over current condition, a current monitoring device can issue a fault signal, triggering an interrupt condition which will cause a processor in the controller to shut down the affected solid state relays very quickly.

An example switch device includes a switching element to connect/disconnect a current path from a power supply terminal to a ground terminal via a load, and an overcurrent protection circuit to limit output current flowing in the switching element to be an overcurrent limit value or less. When an output short circuit of the load is detected, the overcurrent protection circuit decreases the overcurrent limit value to be lower as a power supply voltage is higher. The overcurrent protection circuit includes a reference current generation portion that includes: a differential amplifier portion, an upper side current generation portion arranged to generate a predetermined an upper side current, a lower side current generation portion arranged to generate a lower side current, and a difference current generation portion arranged to output a difference current based on the lower side current and the upper side current, as the reference current.