WorldWide Drilling Resource

Faults by Bill Corey Pentair Water Training Institute Last month, we talked about the ground fault, but there are other system- related issues which can cause damage to a drive. Over- or undervoltage are a couple of faults which affect several parts of the nation. Texas, for example, is known to have a lot of low voltage. Be- cause of this, when I was in Texas and asked why they didn’t like to use drives, the answer was low voltage. So I asked how low the voltage went. The answer was 230 volts. Then I said, I meant the lowest it goes, and the guy shot back it was 190 volts. I said the drive works 190-265 volts. He complained I tricked him, but all I did was overcome an objec- tion he had. What is the real problem with using low voltage? It takes just a little under- standing of electricity to know that as your voltage goes down, your amperage goes up; and when your voltage goes up, the amperage goes down. Amperage is what does the work and voltage is what gets the amperage to where you need it. So if the voltage goes down, it can’t push as hard; the amperage starts to build up, and things get hot. Too much amperage can cause the windings of the motor to get hot, melt the varnish on them, then touch each other, and short out. In North America, we have a choice of 115-volt or 230- volt for single phase. Our three-phase systems can go as high as 460 volts; and in Canada they also use a 575-volt system. Another voltage used here is 208 volts. Remember, as voltage goes down, amperage goes up. If you have a 208- volt system - and there are lots of 208- volt systems in Florida - your amperage is higher. Motor manufacturers are re- quired by law to build in a ±10% which allows a motor to run from 207-253 volts if it is labeled 230 volts. However, a 208- volt system also has a ±10% which allows for 187-220 volts. This is fine if you are on the high side, but if you go too low, those nice copper-colored wires will turn black. The job of the drive is to rectify the voltage so it always puts out 230 volts, single or three phase. Not all drives have this ability, but those that do make it easier to work in a place like Texas. This also means you never need to use a motor that is not 230 volts. It also helps reduce inventory. Next month, we’ll take a look at a fault called dry run. Bill admin@ worldwidedrillingresource.com 69 WorldWide Drilling Resource ® MAY 2013