This discussion revolves around replacing traditional bridge rectifiers with ultrafast rectifiers to improve efficiency and reliability. The system is fed with a 52V CT Transformer, leading into two 6A diodes. While a small current is drawn off and filtered to power the timing electronics, the unfiltered output from the diodes is used to switch some standard T03 transistors, which pulse 24V solenoids on and off.
Thus, the 50Hz unfiltered supply gets switched at approximately 1Hz and operates at a 50% duty cycle.
These units often run around 20 hours a day for over 20 years. Despite their simplicity, they've performed reliably.
The initial unit I encountered had shorted diodes. In a pinch, with no suitable replacements available and the customer urgently needing a solution, I attached a 35A 600V bridge rectifier to the side plate, utilizing only half of it.
As I encountered more of these units over time, I adopted the same approach without much thought. I've probably repaired around 100 of them.
Fast forward four to five years—I received a couple back with shorted bridge diodes!
Again, without much consideration, I replaced them with a 50A 600V bridge. Imagine my surprise when, a year later, more came back with shorted bridges.
This prompted me to contemplate the problem. Why did most run for 20 years without issue, while a few failed using the 50A diodes?
I concluded that it must be voltage spikes getting into the system, possibly from other electrically noisy equipment or poor wiring locations.
The original units have since been succeeded by newer versions. These newer models, while utilizing microcontrollers and communication lines for adjustments, still rely on feeding raw unfiltered DC to operate the solenoids.
However, these updated versions have switched to using TO220 DL, 20A 800V diodes in the same slot as the original 6A diodes. Additionally, they've added a couple of varistors across the input supply, presumably to mitigate incoming noise.
Inspired by these changes, I began outfitting the older units with DL diodes and similar varistors.
Since then, I have almost not received any complaints back relating to this issue, reinforcing my preference for those diodes and varistors.
This trend motivated my search for even better diodes to replace the bridges in the latest modules I've been working on, along with fitting varistors across the supply input.
It's crucial; a misstep could jeopardize my relationship with my overseas customer, and I wish to avoid that at all costs.
Today, I wrapped up these replacements and now need to pack and ship everything back. We shall see what happens next.
Thanks to everyone for your contributions; your insights have been immensely valuable.
The same company that produced the modules mentioned above also manufactures another device I've serviced for years. This device operates similarly, using a 52V CT Transformer and two 6A diodes to supply power. It efficiently runs for approximately 20 hours a day over a span of 20 years, showcasing notable durability. When the first device I handled had shorted diodes, I made a quick fix using a 35A 600V bridge. As I began to encounter more units, I kept using this solution without overthinking it. However, it wasn't until I received several back with the bridges shorted that I took pause. Most had performed splendidly using 6A diodes, so I pondered the reason behind those few that failed using 50A diodes. I surmised that voltage spikes might be infiltrating the systems, possibly due to other noisy electrical components or poorly installed wiring. The newer systems now utilize more advanced features while retaining their basic architecture, opting for TO220 DL, 20A 800V diodes and incorporating varistors to suppress incoming electrical noise. With this knowledge in mind, I began upgrading older units with DL diodes and varistors, which led to a significant drop in return repairs. This experience, coupled with my desire to find improved diodes for the most recent modules, solidifies why I prioritize high-quality components for critical systems. I aim to avoid any potential issues that may jeopardize my collaborative relationships, particularly with overseas clients. After completing these units, packing them for shipment was my next step—time will reveal the success of these modifications. A heartfelt thanks to everyone for sharing your expertise, it has made a significant difference.
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