The Advisory Boar

By Abhijit Menon-Sen <ams@toroid.org>

Fighting voltage fluctuations

2017-01-16

The mains power supply in Lweshal is dismal.

There are frequent outages, of course—the transformer in the village blew up earlier this year, and we had no power for a week. Two or three times in the summer (when forest fires were burning everywhere) a tree fell on the line and cut off power for a few days. There's a big fuse near Mauna which seems to keep melting down. But none of that is really a surprise in a remote area.

The unpleasant surprise was how bad the supply could be when there's no outage. For some reason, extreme voltages are quite common. I've seen the mains voltage at a record low of 25V for several hours once, and we've had whole days when it stayed around 60–90V—voltages so low that the electricity meter stayed off, even though our 9W LEDs inside would light up. Free power!

High voltages don't last nearly as long, but we've seen spikes of 300V and more on occasion. It's difficult to decide which condition is more destructive. High voltages fry appliances, but persistent low voltages where some lights appear to work encourage people to draw more current than their circuits can safely carry—and in a place where people use 1.0mm² wire even for 16A circuits, and nobody has any earthing, that isn't something to be taken lightly.

Either way, voltage fluctuations blew up our UPS twice. The first time we didn't have any sort of voltage regulator installed. After having to pay for a new logic board, we installed a custom-made "constant voltage transformer" (a big auto-transformer with a voltage meter). It clicked a lot to indicate its displeasure, and we had to take it back to the shop to make it cut off the output altogether if the voltage was too low (but why didn't it do that to begin with?). Then the next fluctuation killed the UPS again.

Accurex DPM-3000

In such a dire situation, only a device with a genuine superhero name could possibly save us, and the Accurex DPM-3000 certainly delivers on that front. I bought one from Amazon, and we installed it upstream of the main distribution board. It doesn't do any voltage regulation, just cuts off the output beyond the predefined low and high voltage thresholds. Here is it in action.

Photograph of Accurex DPM-3000

It has worked correctly in various low-voltage conditions (we've had a 130V supply for most of the past two days). It has high- and low-voltage bypass modes that I have never tried, and an optional output timer that restores power to the house only if the power stays on for two minutes. It's useful that it displays the input voltage (even when the output is cut off), and the 32A circuit breaker is very handy when we're working on the distribution board.

Other Amazon customers assured me that the device makes no noise during operation, but of course it does. It clicks away merrily, but it's a small price to pay for reliable voltage limits.

Update (2017-04-23): Our low- and high-voltage records for the Accurex are 43V and 592V respectively (both voltages persisted for some hours before returning to normal).

The wonders of modern refrigeration

2017-01-14

I have never had a refrigerator that was not subject to periodic power failures. The severity and frequency of the outages varied from several small interruptions per day to extended power failures lasting sixteen hours or more; the former could be ignored, while the latter usually meant throwing everything out and starting afresh.

As I grew up and started working with computers, a succession of power backup devices entered my life, and I eventually became accustomed to “uninterrupted” power, but it was strictly rationed. I was never able to connect anything but the computers and networking equipment to the UPS, and certainly nothing like a refrigerator.

So I have never experienced refrigeration as it is meant to be.

Until now. Thanks to our solar power setup, we have been able to keep our refrigerator running without interruptions for several weeks on end. Suddenly it feels as though we have a magical new refrigerator in which food doesn't spoil. Coriander and green chillies stay fresh and usable for days. Cream skimmed off the top of boiled milk is something we can collect for the rare fettucine alfredo. Our precious cheese collection is something we can enjoy at leisure. These days we don't have much in the way of leftovers, and we can use fresh vegetables from our kitchen garden often enough that we store only a few in the refrigerator, but everything remains usable for an absurdly long time.

Today is a festival that has something to do with a water monster. I'm not very clear about the details, but there's a crocodile (or half a crocodile) involved in some way, and that's good enough for me. So in honour of the water monster, we cleaned the fridge today. Nothing was spoiled, and the dreaded “fridge smell” was very faint. The fridge is now spotless, and the monster is appeased.

Makara sculpture - Jain Museum , Khajuraho India

Sometimes the most mundane of insights can seem profound if it comes from experience: modern refrigeration is pretty nice.