Posted in Design on October 22nd, 2024
Selection of Variable Frequency Drives
The size of a variable frequency drive (VFD) should be based on motor voltage and current and not on the torque or power rating. The voltage and full load current information can be taken from motor nameplate or datasheet.
[caption id="attachment_18665" align="aligncenter" width="640"] Induction Electric Motor Nameplate[/caption]
While the motor can be rated...
Posted in Design on October 17th, 2024
Power Factor Correction and Harmonic Resonance: A Risky Combination
Capacitors are intended to solve problems, but if not properly specified, they can also create new ones.
Industrial and commercial customers are always examining their monthly electrical usage for cost-saving opportunities. Installing power factor correction capacitors can help reduce penalties imposed by utilities, often leading to a quick return on investment. In locations like hospitals and paper mills, the payback...
Posted in Design on October 16th, 2024
Variable Frequency Drive Cable Length Resonance Frequency
This is a continuation of the article Effect of Cable length on Variable Frequency Drive.
Cable Resonance
When dealing with Variable Frequency Drives (VFDs), the cable length between the VFD and the motor can introduce certain electrical challenges, one of which is cable resonance. Resonance occurs when the frequency of the drive's output waveform interacts with the natural frequency of...
Posted in Design on October 14th, 2024
Effect of Cable Length on Variable Frequency Drive
Every cable has, apart from its resistance, certain inductance and capacitance. The inductance and capacitance is roughly equally distributed along the cable length. Inductance L and capacitance C in a circuit create a resonance.
[caption id="attachment_18636" align="aligncenter" width="600"] Equivalent Circuit of Long Cable[/caption]
The formula for cable resonance is
[pmath size=20]omega_res=1/{l*sqrt{LC}}[/pmath]
Where:
ω =...
Posted in Design on October 11th, 2024