Fluke - Checking voltage-frequency ratio on variable speed drives

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With their unique triggering and measuring functions, Fluke ScopeMeter 190 Series II portable oscilloscopes are ideal for analyzing the voltage-frequency ratio of pulse-width-modulated variable speed drives.

Variable Speed Drives

Variable Speed Drives (VSDs) provide a convenient and affordable method for varying the speed of robust ac motors. When connected to the mains, the rotation speed of an ac motor is directly related to the mains frequency and the number of poles of the motor. Traditionally an external gearbox was the only way to work with different speeds. This all changed with the introduction of high-power semiconductors, which made it possible to build variable speed drives by electronically creating a supply voltage that operates at different frequencies. This has, however, created the need for new measurement capabilities, which are provided by the Fluke 190 Series II portable oscilloscope.

Pulse Width Modulation

AC drives using Pulse Width Modulation (PWM) have found their way into many applications such as fans, pumps and conveyor belts driven by squirrel- cage asynchronous ac motors. These motors are robust and require little maintenance since they have no brushes that would need regular replacement...

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