Semiconductor-based DC transfer switch
Systems for method for a semiconductor-based DC transfer switch. The semiconductor-based DC transfer switch uses two individual circuit breakers that are mechanically interlocked in such a way that only one of the two circuit breakers can be closed at any time. An actuator, such as a motor, operates mechanical arms that interact with the handles of the circuit breakers. At least one of the circuit breakers is a semiconductor-based DC circuit breaker.
1 . A transfer switch that operates between a first power source and a second power source, wherein the second power source is a first DC power source, the transfer switch comprising:
a first circuit breaker connected to the first power source and a load, the first circuit breaker including a first circuit breaker handle that opens and closes the first circuit breaker,
a second circuit breaker connected to the second power source and the load, the second circuit breaker including a second circuit breaker handle that opens and closes the second circuit breaker, wherein the second circuit breaker comprises a semiconductor-based DC circuit breaker, and
an actuator configured to operate a second circuit breaker mechanical arm and a first circuit breaker mechanical arm that interact with the second circuit breaker handle and the first circuit breaker handle, respectively, such that the second circuit breaker and the first circuit breaker are mechanically interlocked, wherein the mechanical interlocking of the second circuit breaker and the first circuit breaker is configured such that only one circuit breaker of the second circuit breaker and the first circuit breaker is closed at any time,
wherein the semiconductor-based DC circuit breaker comprises:
an air gap in series with two power MOSFET modules, wherein a source of one of the two power MOSFET modules is connected to a drain of the other of the two power MOSFET modules, wherein the two power MOSFET modules are connected in series; and
an air gap actuator including a switching device configured to open the air gap,
wherein the switching device is configured to be turned on for just long enough to open the air gap and then turned off.
2 . The transfer switch of claim 1 , wherein the first power source is an AC power source.
3 . The transfer switch of claim 1 , wherein the semiconductor-based DC circuit breaker further comprises:
a sensing and control circuit configured to control the semiconductor-based DC circuit breaker,
wherein the two power MOSFET modules have a higher threshold voltage than a system voltage of the semiconductor-based DC circuit breaker.
4 . The transfer switch of claim 1 , wherein the first power source comprises utility power and the second power source comprises power from a renewable power source.
5 . A method for switching between a first power source and a second power source using a transfer switch, the transfer switch comprising a first circuit breaker connected to the first power source, a second circuit breaker connected to the second power source, and an actuator connected to a first circuit breaker mechanical arm and a second circuit breaker mechanical arm, the first circuit breaker mechanical arm and the second circuit breaker mechanical arm being configured to interact with a first circuit breaker handle and a second circuit breaker handle, respectively, such that the first circuit breaker and the second circuit breaker are mechanically interlocked, the mechanical interlocking between the first circuit breaker and the second circuit breaker being configured such that only one circuit breaker of the first circuit breaker and the second circuit breaker is closed at any time, wherein the second circuit breaker comprises a semiconductor-based DC circuit breaker, the method comprising:
providing the transfer switch with the first circuit breaker closed and the second circuit breaker open;
opening the first circuit breaker, opening the first circuit breaker comprising rotating the actuator in a first rotational direction, such that:
the first circuit breaker mechanical arm moves the first circuit breaker handle of the first circuit breaker from an ON position to past an OFF overcenter position; and
the second circuit breaker mechanical arm moves the second circuit breaker handle of the second circuit breaker below an ON overcenter position, which leaves open the second circuit breaker; and
closing the second circuit breaker, closing the second circuit breaker comprising further rotating the actuator in the first rotational direction, such that the second circuit breaker mechanical arm moves the second circuit breaker handle to an ON position,
wherein the semiconductor-based DC circuit breaker comprises:
an air gap in series with two power MOSFET modules, wherein a source of one of the two power MOSFET modules is connected to a drain of the other of the two power MOSFET modules, wherein the two power MOSFET modules are connected in series; and
an air gap actuator including a switching device configured to open the air gap,
wherein the switching device is configured to be turned on for just long enough to open the air gap and then turned off.
6 . The method of claim 5 , further comprising:
opening the second circuit breaker, opening the second circuit breaker comprising rotating the actuator in a second rotational direction opposite the first rotational direction, such that:
the second circuit breaker mechanical arm moves the second circuit breaker handle from the ON position to past an OFF overcenter position; and
the first circuit breaker mechanical arm moves the first circuit breaker handle below an ON overcenter position, which leaves open the first circuit breaker; and
closing the first circuit breaker, closing the first circuit breaker comprising further rotating the actuator in the second rotational direction, such that the first circuit breaker mechanical arm moves the first circuit breaker handle to an ON position.
7 . The method of claim 6 , wherein the first rotational direction is counterclockwise, and the second rotational direction is clockwise.