Mike Dolt Enterprises
Mike Dolt Enterprises
User: ArchieMedes, Location: Antipolo City
Asked on: Wednesday, June 1, 2011 at 10:25 pm EDT
Answered on: Tuesday, May 14, 2024 at 6:06 am EDT
Question: I have a question about our diesel generator (400kW), the installation's total load normally is about 50kW and we have another load also 50kW which has a switching controller (thyristor cycle controller) which switches the 50kW load at high speed the fastest is 1 cycle for 50 Hz, on and off. We noticed that if this 50kW load is being controlled (switched on and off) by the thyristor, the generator's voltage fluctuates as well. If that load is not used and the load is only lighting or motors, , the generator's is not fluctuating.My question are:The generator is obviously over sized but still being affected, why?Is there any kind of voltage stabilizer / regulator to eliminate the voltage fluctuation of the generator?Thanks in advance
Why is the Generator Affected by the Thyristor Load?
The thyristor cycle controller rapidly switches the 50 kW load on and off, causing sudden changes in the current drawn from the generator. These rapid current changes induce voltage fluctuations in the generator's output due to: Generator Impedance
The generator has an inherent impedance that causes a voltage drop when current flows through it. The high-speed switching of the thyristor load results in significant voltage drops and spikes.
Exciter Response Time
The generator's exciter system takes time to adjust the field current and maintain voltage stability. The fast switching of the thyristor load can overwhelm the exciter's response time, leading to voltage fluctuations.
Voltage Stabilization Options
To eliminate the voltage fluctuations, you can implement the following voltage stabilization options:1. Automatic Voltage Regulator (AVR)
An AVR is a device that monitors the generator's output voltage and adjusts the exciter field current accordingly to maintain a stable voltage. This helps compensate for load variations, including those caused by the thyristor switching.2.
Dynamic Voltage Restorer (DVR)
A DVR is a more advanced voltage stabilization device that injects voltage into the generator's output when voltage fluctuations occur. This provides a more responsive and effective voltage regulation than an AVR.3.
Thyristor-Based Voltage Regulator
This type of regulator uses thyristors to control the voltage by adjusting the firing angle of the thyristors. It offers fast response times and can effectively handle the high-speed switching of the thyristor load.4.
Motor-Generator Set (M-G Set)
An M-G set consists of a motor connected to a generator. The motor is controlled to provide a stable voltage to the generator's output, isolating it from the fluctuations caused by the thyristor load.
Oversized Generator Issue
While the generator's oversized capacity may not be directly causing the voltage fluctuations, it can make the problem more noticeable. A smaller generator with a tighter regulation range would be more likely to maintain voltage stability under the variable load conditions. Flag for review