Abstract: A ventilation system for an electrical equipment enclosure is provided. The ventilation system includes a first vent disposed at an interior of the enclosure; a second vent disposed at an exterior of the enclosure and located away from the first vent along an air flow path, which may be circuitous; at least one inner shutter held in an open position with respect to the first vent; and at least one outer shutter held in an open position with respect to the second vent; the at least one inner shutter and the at least one outer shutter each being configured to automatically transition from an open position to a closed position in response to air pressure increase.

Abstract: A drive system for driving a multi-phase motor (such as a three-phase AC motor) or other load. Where a transformer is used, the transformer may have a disconnected wye configuration on the secondary side. The system may also utilize the average or other combination of DC bus voltages of inverters for each load phase, to provide feedback control.

Abstract: An inverter system for driving electrical loads such as multi-phase induction motors is disclosed utilizing five single-phase inverter cells configured in a wye configuration. Inverter cells such as neutral-point-clamp inverter cells are configured to generate a voltage waveform between two output terminals and further configured with a terminal providing a neutral voltage reference point with respect to each of the two output terminals. The inverter cells may be configured with the neutral voltage reference points connected together and with one output terminal from each inverter cells connected together to provide three outputs of the inverter system at different voltage phases and with the common neutral reference point as the wye connection of the three outputs. The other three single phase inverter cells may be added to each of the three outputs to boost the output voltage of the inverter system and decrease the maximum voltage requirements on each inverter cell.

Abstract: A drive system for driving a multi-phase motor (such as a three-phase AC motor) or other load. Where a transformer is used, the transformer may have a disconnected wye configuration on the secondary side. The system may also utilize the average or other combination of DC bus voltages of inverters for each load phase, to provide feedback control.

Abstract: A transformer controller for a drive isolation transformer is provided. The transformer may include multiple sets of primary windings as an input, and the transformer controller may include multiple branches coupled between a power source and the transformer. Each branch may be coupled to its own primary winding on the transformer, and may include one or more components, such as an isolation switch, a fuse, contactor, or circuit breaker. One or more of the branches may include a pre-charge reactor to limit inrush or capacitor charging current occurring during startup, and may include a pre-charge contactor to remove the pre-charge reactor from the circuit when the startup process has reached a certain level (e.g., the charging or inrush current has dissipated, or a DC bus reaches a charged state).

Abstract: An 18n-pulse rectifier for AC drive systems having a separate DC bus for each output phase is provided, where n=any positive integer. The rectifier uses three separate phase rectifiers, one for each output phase of a transformer, each comprised of 2n six-pulse diode bridges connected in series or parallel. Each phase rectifier may be supplied with n unique sets of phase inputs from a transformer secondary winding. In some configurations, the n sets of inputs provided to each rectifier are separated by 60/n degrees of phase (when n is greater than 1), while the corresponding inputs to neighboring rectifiers are separated by 20/n degrees of phase. In a 36-pulse example, the phase offsets for the inputs provided to the rectifiers may be ?25° and +5° from the transformer primary winding (for the first rectifier), ?15° and +15° from the primary winding (for the second rectifier) and ?5° and +25° from the primary winding (for the third rectifier).

Abstract: An inverter system for driving electrical loads such as multi-phase induction motors is disclosed utilizing five single-phase inverter cells configured in a wye configuration. Inverter cells such as neutral-point-clamp inverter cells are configured to generate a voltage waveform between two output terminals and further configured with a terminal providing a neutral voltage reference point with respect to each of the two output terminals. The inverter cells may be configured with the neutral voltage reference points connected together and with one output terminal from each inverter cells connected together to provide three outputs of the inverter system at different voltage phases and with the common neutral reference point as the wye connection of the three outputs. The other three single phase inverter cells may be added to each of the three outputs to boost the output voltage of the inverter system and decrease the maximum voltage requirements on each inverter cell.