Terminology

Terminology and industry Jargon

Catch on Fly / Flying Restart / Flying Start / Pick up (Industrial, Electrical, Mechanical) – A feature some VFDs posses, which allows starting an electric motor that is already running. Two methods of doing this are called “Catch on Fly with Current Limit” and “Speed Search”. The reason this is non-trivial is because the frequency and phase have to be matched up to what is happening in real-time with the motor.

VFD / Variable Frequency Drive (Industrial, Electrical, Mechanical) – A VFD is used to control an electric motor’s speed, and generally have a large number of configurable options for tuning to a specific motor and application, allowing for smooth starts and stops and monitoring of faults. Drives tend to have multiple inputs and outputs, allowing things such as speed control by analog voltage input, fault outputs, etc.

Duty Cycle – The “on time” over the periodĀ of a waveform. For example, a 50% duty cycle of a square wave would mean that the signal is on for exactly the same period of time as it is off. Deliberate control of this ratio is called PWM.

PWM – Pulse Width Modulation. The deliberate control of the duty cycle of a waveform. This technique is used in switching power supplies to regulateĀ the resulting output voltage.