In one aspect, a modular static transfer switch is provided. The module static transfer switch includes an output configured to couple to a load, a first input configured to couple to a first power source, and a second input configured to couple to a second power source. The modular static transfer switch further includes a plurality of sold-state switch modules each comprising at least one solid-state switch. A first plurality of the solid-state switch modules are coupled in parallel between the first input and the output, each configured to selectively couple the first power source to the output using the at least one solid-state switch. A second plurality of the solid-state switch modules are coupled in parallel between the second input and the output, each configured to selectively couple the second power source to the output using the at least one solid-state switch.

In one aspect, a modular static transfer switch is provided. The module static transfer switch includes an output configured to couple to a load, a first input configured to couple to a first power source, and a second input configured to couple to a second power source. The modular static transfer switch further includes a plurality of sold-state switch modules each comprising at least one solid-state switch. A first plurality of the solid-state switch modules are coupled in parallel between the first input and the output, each configured to selectively couple the first power source to the output using the at least one solid-state switch. A second plurality of the solid-state switch modules are coupled in parallel between the second input and the output, each configured to selectively couple the second power source to the output using the at least one solid-state switch.

A resettable electronic fuse for a high-power device such as a power tool, a battery pack for the power tool, or a battery pack charger. The resettable electronic fuse is connected in a current path of the device and is operable or configured to selectively interrupt current through the resettable electronic fuse based on a detected condition of the device (e.g., a detected fault condition of the device). The resettable electronic fuse is also configured to be reset after a detected fault condition has ended. In some embodiments, the resettable electronic fuse is configured to reset itself. In other embodiments, the resettable electronic fuse is configured to receive a signal (e.g., from a device controller) to reset.

A current interrupting device includes a current limiting element on a power supply path from a predetermined power supply to a load device. The current limiting element is configured to exhibit a current limiting action when current flowing in the power supply path exceeds a first current threshold value. The current interrupting device further includes a current diversion path switch, and a controller programmed to control on and off of the current diversion path switch. The controller is programmed to switch a current diversion path switch on from an off state when it is detected that current flowing in the current limiting element is limited to a second current threshold value after the current flowing in the current limiting element has exceeded the first current threshold value, and switch the switch off again after a predetermined switched-on holding time has elapsed since the switch has been switched on.

A current interrupting device includes a current limiting element on a power supply path from a predetermined power supply to a load device. The current limiting element is configured to exhibit a current limiting action when current flowing in the power supply path exceeds a first current threshold value. The current interrupting device further includes a current diversion path switch, and a controller programmed to control on and off of the current diversion path switch. The controller is programmed to switch a current diversion path switch on from an off state when it is detected that current flowing in the current limiting element is limited to a second current threshold value after the current flowing in the current limiting element has exceeded the first current threshold value, and switch the switch off again after a predetermined switched-on holding time has elapsed since the switch has been switched on.

Provided is an apparatus and method for protecting against unsafe electric current conditions. A protections circuit may be used in a device, such as an electric grill, that has one or more electric loads, such as heating elements. The protection circuit may protect against various failure scenarios, including, without limitation, instances of ground fault, over current, driver failure, and failure of a microprocessor. In response to a failure, the protection circuit may trip a latch relay or disable a triac driver to stop current from flowing.

A method and system are provided to control circuit breaker operations. In the method and system, near-field RF signal is monitored at or around electrical contacts of the circuit breaker using at least one near-field radio frequency (RF) sensor, and far-field RF signal away from the contacts of the circuit breaker are monitored using at least one far-field RF sensor. A rate of change of current over time is also monitored on the circuit using at least one sensor. An arc fault on the circuit is detected based on the monitored near-field RF signal, the monitored far-field RF signal, and the monitored rate of change of current. A tripping operation is implemented on the circuit breaker to disconnect the power supply from the circuit, in response to the detection of the arc fault.

A composite circuit protection device includes: a first positive temperature coefficient (PTC) component; a first voltage-dependent resistor (VDR); a second VDR; and a plurality of conductive leads that correspondingly connect to the first PTC component, the first VDR and the second VDR. The second VDR and the first PTC component are electrically connected in series, the first VDR is electrically connected to the series connection of the first PTC component and the second VDR in parallel, and the first VDR has a varistor voltage greater than that of the second VDR as determined at 1 mA.

A composite circuit protection device includes: a first positive temperature coefficient (PTC) component; a first voltage-dependent resistor (VDR); a second VDR; and a plurality of conductive leads that correspondingly connect to the first PTC component, the first VDR and the second VDR. The second VDR and the first PTC component are electrically connected in series, the first VDR is electrically connected to the series connection of the first PTC component and the second VDR in parallel, and the first VDR has a varistor voltage greater than that of the second VDR as determined at 1 mA.

Disclosed herein are various embodiments of devices and related methods for detecting an electrical arc event using a motor management relay and for suppressing the electrical arc event. The motor management relay may incorporate an optical arc-flash sensor configured to detect an optical event. Control logic may analyze the optical event and determine whether the optical event corresponds to an electrical arc event. When an electrical arc event is detected an instruction may be issued via a control port in communication with the control logic to implement a protective action. According to various embodiments, a plurality of sensors for monitoring electrical characteristics of a motor may also be in communication with the control logic. Input from the sensors may be analyzed in order to determine whether the optical event corresponds to an electrical arc event.