- Unbalanced current consumption
A condition in which the three-phase currents in a system differ significantly, which may cause overheating in motors or transformers, vibration, and reduced efficiency.
- Undervoltage releases
Devices that automatically disconnect the circuit when voltage drops below a defined threshold. Used in motor starters and breakers for safety purposes, ensuring machines do not restart unexpectedly after voltage recovery.
- Use of reactor capacitor
Refers to the use of series reactors in power factor correction capacitor banks to limit inrush currents and avoid resonance with harmonics. These are often detuned reactors, tuned below the lowest harmonic to prevent overload or equipment damage.
- Utilization categories
Standard classifications (e.g., AC-1, AC-3, AC-4) that define the electrical and mechanical stresses expected on switching devices such as contactors and circuit-breakers during operation. These categories are essential for proper component selection.
- Utilization categories for contactors, motor starters
These include:
- AC-1: Non-inductive or slightly inductive loads (e.g., resistive heating).
- AC-3: Starting and stopping squirrel-cage motors during normal operation.
- AC-4: Inching and plugging duties – frequent start-stop cycles with high current and electrical wear. Plugging causes reverse torque; inching requires fast repetitive cycles. Devices used in these duties must withstand high mechanical and electrical stress.
- Utilization categories for switch-disconnectors
Defined to indicate their ability to make, carry, and break specific currents under load. These may also need to be rated for motor starting applications, including plugging conditions in some systems.
- Utilization categories for switching elements
Applies to all switching devices, such as relays or PLC output modules. The assigned category ensures that the device is suitable for the type of load and switching behavior expected.
Published by Leonardo Tomás Cardillo
https://www.linkedin.com/in/leonardocardillo
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