Abstract: Systems and methods for controlling potentially damaging inrushes of current to the capacitor bank of an electric drive system when the voltage on the capacitor bank is low. In one embodiment, a variable speed drive has a converter that converts AC power to DC power, a capacitor bank that receives the DC power, and an inverter that converts the DC power stored by the capacitor bank to AC output power. The converter has three sections that rectify the phases of three-phase input power. Each section has at least one controlled rectifier component, and the rectifier components have switches connected to them in parallel. When the voltage on the capacitor bank is low, the controlled rectifiers and switches are controlled to prevent dangerously high inrushes of current to the capacitor bank.

Abstract: Systems and methods for driving downhole equipment using a variable speed drive that has a switching mechanism between a first, constant-voltage capacitor bank and a second capacitor bank to control the voltage on the second capacitor bank, thereby enabling generation of a six-step output waveform while maintaining low input harmonics. In one embodiment, a variable speed drive has a converter section, an inverter section, two capacitor banks and a chopper. The converter section is controlled by a controller to convert AC power to DC power and charges the first capacitor bank to a substantially constant voltage. A chopper selectively couples the first capacitor bank to the second capacitor bank and thereby controls the voltage on the second capacitor bank. The inverter section can then produce a six-step output waveform at the voltage of the second capacitor bank. The variable speed drive can operate alternately in a pulse width modulation mode.

Abstract: Systems and methods for controlling potentially damaging inrushes of current to the capacitor bank of an electric drive system when the voltage on the capacitor bank is low. In one embodiment, a variable speed drive has a converter that converts AC power to DC power, a capacitor bank that receives the DC power, and an inverter that converts the DC power stored by the capacitor bank to AC output power. The converter has three sections that rectify the phases of three-phase input power. Each section has at least one controlled rectifier component, and the rectifier components have switches connected to them in parallel. When the voltage on the capacitor bank is low, the controlled rectifiers and switches are controlled to prevent dangerously high inrushes of current to the capacitor bank.