Control Panel U blog

Summary: Circuit breakers are sized according to rules established by codes and standards. For common applications, a 250% x motor FLA maximum size limitation is used.  However, this is different when drives are used, or when special circuit protection types are used. Introduction Circuit breakers are commonly used in circuit protection of motor circuits.  Size it wrong and you could end up with nuisance tripping, or even worse insufficient circuit protection. Sizing a circuit breaker for a motor load isn't overly complicated but there are some rules to follow, and a few things to check.  This article simplifies how circuit breakers are sized for motor loads in the US. What can go wrong? Do you ever wonder why a breaker isn't sized to match the motor full load amp (FLA) rating?  What would happen? Likely your circuit breaker would trip when the motor is turned on.  Electric motors have a higher current at start up.  This is sometimes referred to as inrush ....

Summary: The choice of overcurrent circuit protection depends on various factors.  The right choice depends on the application and functions required. Introduction Many, many years ago, there were two overcurrent protection options... breakers and fuses.  Over time new circuit protection options have appeared on the scene.  Millions of electric motors are in operation in the US, and each one needs overcurrent protection.  These circuit protection devices play a very important role, not only in opening motor circuits, but also in how the control panel is designed, built, installed, and operated.  In this article we will cover the main options, their main benefits and disadvantages, as well as where they often function the best. What are the options? There are several different types of circuit protection used in motor control circuits, each bringing its own mix of value and use.  The following are the most popular: Fuses - These devices use a self-sacrifici...

  Summary: Have you ever realized after the fact that a higher SCCR is needed? In this blog we will discuss the use of fuses, and why this may not fix insufficient SCCR. Wha t's the problem? The NEC requires that control panels have sufficient SCCR. This is the amount of short-circuit current a control panel is rated to endure should a short-circuit occur. There could be a lot of available short-circuit current or a little. It all depends on what the electrical system can deliver. Usually, the cause for the panic comes when it is discovered that a higher SCCR is needed AFTER the control panel is built and installed in the field. A simple quick fix would be ideal in this situation. Often the idea of adding a fuse comes up. Why add a fuse? A fuse in the simplest terms is a strip of metal, usually copper or some alloy, in a protective tube that melts very fast in the event of a steep rise in current, like a short circuit. This quickly opens the circuit and halts the damaging h...