RESISTOR CHOPPERS SLOW OVERSPEEDING FANS

摘要

Fans don't normally need a braking resistor and chopper, but when they are operating in a closed system, a situation may arise where one fan will over-speed the next and the DC bus voltage on their motor drives will then rise. Here, John Mitchell, business development manager of CP Automation, reports on the case of GA Pet Food Partners in Leyland, Lancashire External dynamic braking choppers are useful to drive manufacturers, panel builders and end users alike. A seventh IGBT (Isolated-Gate Bipolar Transistor) for the chopper in a six-pulse drive is one way drive manufacturers can reduce the cost of the product by rating the IGBT to a given torque and duty level Some six-pulse off-the-shelf AC drives manufactured today have a seventh IGBT built in as standard.