An Inverter for Traction Applications

An inverter configuration with an auxiliary shutoff circuit designed for traction applications is described. The auxiliary shutoff energy adds to the main shutoff energy providing the necessary shutoff capability at stall and low motor speeds where maximum traction is required. The auxiliary shutoff is automatically programmed so that its effect diminishes gradually as the motor speed increases. Such programming results in a reliable inverter where the volt-ampere rating of thyristors are best utilized to provide active power and safety margin. The inverter can be used in conjunction with a chopper, providing variable dc voltage, to convert a fixed dc voltage source to a variable frequency and amplitude ac source. The inverter can also be used in conjunction with a controlled rectifier, providing variable dc voltage, to convert the 60-Hz fixed frequency and voltage commercial supply to a variable voltage and frequency ac supply.