Uninterruptible Power Supply (UPS)
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How to secure a market UPS?
Use an energizing switch with a contactor in series before the UPS to block unstable mains and prevent damage caused by repeated cutoff cycles.
In areas with unstable electricity, rapid on-off “flickering” can damage a UPS. To prevent this, we use a simple custom system: a contactor controlled by a manual reset (NO) button.
How It Works
When mains power returns, the contactor stays open, keeping the UPS safely disconnected.
You press the NO button to energize the contactor and allow power to flow to the UPS.
If the power cuts again, the contactor instantly drops out, isolating the UPS and preventing harmful cycling.
Power stays disconnected until you manually decide it’s stable and press the button again.
This setup protects the UPS from unstable supply, prevents repeated stress cycles, and ensures safer, more controlled restarts.
Building Your Own Custom UPS: A DIY Guide
Building your own uninterruptible power supply (UPS) offers a flexible and repairable alternative to a pre-built unit. Here’s a basic guide on how to assemble a custom UPS.
1. Electrical Connections:
Main Power Supply:
Use NO to make a direct connection in between 230v power supply and the output sockets of the assemble UPS.
Inverter Connection:
Use NC to make a direct connection in between Inverter output and the output sockets of the assemble UPS.
Battery and Charger:
(Safe-charging Current for 12v 7ah lead-acid battery = 0.7 A)
Connect the positive terminal of the battery to the positive input of the inverter.
Connect the negative terminal of the battery to the negative input of the inverter.
Connect the output of the battery charger to the positive and negative terminals of the battery.
Socket Connections:
Connect all your output sockets in parallel. These are the outlets where you'll plug in your devices.
Be mindful of the total power draw. A 12V 7Ah battery powering a 1.4A load at 230V will only last about 13 minutes. Avoid connecting high-power appliances to prolong the battery's runtime.
2. Control Logic
The contactor is the heart of this system, automatically switching between power sources without needing a complex transfer switch (like an ATS or SATS).
When Main Power Is Present: The contactor's coil is energized by the main power, which closes the NO contact. This connects your devices directly to the main power supply and opens the NC contact, disconnecting the inverter.
During a Power Outage: The coil loses power, causing the NO contact to open (disconnecting the main power) and the NC contact to close. This instantly connects your devices to the inverter, which is powered by the battery.
3. Safety and Maintenance
A. Safety First:
Overcurrent Protection: Use fuses on both the main power line and the inverter's output to prevent damage from power surges.
Battery Charging: Ensure your charger is correctly sized for your battery and includes overcharge protection to extend battery life.
Grounding: Properly ground all components and the chassis to prevent electric shock.
Enclosure: House all components in a suitable enclosure to protect them from dust, moisture, and accidental contact.
B. Regular Maintenance:
Periodically check the battery's charge and inspect all connections for corrosion or loose wires.
Test the system regularly to ensure it switches over correctly during a simulated power outage.
Replace components as needed to keep the system running smoothly.
The Advantages of a Custom Build
This DIY approach offers several benefits:
Modular Design: Using contactors creates a modular system where components can be easily repaired or upgraded.
Flexibility: You can customize the system to match your exact power needs, whether you need a smaller battery for a few minutes of runtime or a larger one for longer protection.
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