DYNAMIC LOADS
Motors, welding equipment and rapidly changing loads can cause voltage fluctuations and supply current peaks. Fast reactive power compensation can help limit these effects, depending on supply impedance, load characteristics and system response.
Capacitor steps are switched by thyristors using controlled switching instead of electromechanical switching contactors. These systems suit rapidly changing loads and frequent operations. Measurement time, control logic and synchronisation with the load determine the actual response; any reactors are selected for the harmonic spectrum and resonance conditions.
Electronic compensators, such as SVGs, control reactive current without relying on capacitor step sizes. Inductive and capacitive capability, response times and available current must be checked under actual operating conditions.
Motor-starting assessment considers current, active and reactive power, voltage drop, acceleration time and starting frequency. Compensation can reduce upstream reactive current demand and help limit voltage drop. Motor torque and the driven load are also considered; the supply must still deliver the motor’s active power demand.
Preliminary installation study and targeted measurements of starting events and operating cycles to define system rating, response and requirements. Technology comparison, assessment of supply interactions and post-installation measurement of results.
General guidance by solution type, using a 400 V low-voltage supply as reference. Ranges summarise the ratings considered and do not imply that all combinations are available. Connection, rating and actual performance must be checked for the project.
| Configuration | Ratings and supply | Features | Checks required |
|---|---|---|---|
| Real-time thyristor-switched compensation | 400 V supply; power and steps sized for the application | Controlled static switching for rapidly changing loads | Total response time, control, harmonics and resonance |
| Continuously controlled electronic compensator | 400 V supply; power sized for the application | Continuous reactive current control | Response, inductive/capacitive capability and operating conditions |
Static switching time and overall system response are different parameters. Ratings, control logic and performance are defined for the application; no single response time applies to all technologies.
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