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: 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...