Patent attributes
A voltage transformer, which is placed between a DC power source (B) and a motor (M1), includes: a voltage sensor (10) and an electric current sensor (11), which senses input and output of electric power to and from the DC power source (B); a buck-boost converter (12) having power control elements, which is placed in a path connecting between power lines (PL1) and (PL2) that establish the connection to the DC power source (B) and the connection to the motor (M1), respectively; and a controller (30) for controlling the buck-boost converter (12). The controller (30) monitors the change in the regenerated power that is supplied to the DC power source (B), based on the outputs from the voltage sensor (10) and the electric current sensor (11), and, if the amount of change in the regenerated power is greater than a predetermined amount, the controller (30) changes the operation mode of the buck-boost converter (12) from a rapid operation mode to a slow operation mode.
