https://www.AutomationDirect.com/circuit-protection
(VID-CP-0009)
Circuit breaker and fuse trip curves (CB Trip curves) explain how a trip occurs based on current and time.
Example:
A Curve
B Curve
C Curve
D Curve
AutomationDirect carries a full selection of industrial circuit protection devices with incredible prices, high stock rates and fast shipping. Trip curves may be called tripping characteristics, current curve, current-time curve or other terms. A trip curve is simply a description of how an overcurrent based on time will trip a fuse or circuit breaker. For this video we’ll focus on breakers but the same applies to fuses. You may see breakers sold based on trip curve. Looking at the curve chart, this axis is time and this one is amperage as a multiple of rated current. It’s obvious at a glance that the lower the current the longer it takes to trip. This is common for most breakers and fuses. The intended use of the device determines the desired curve. This curve has 3 different curves in one chart because the breakers for this chart are available in B, C or D curves. Lets look at the range of typical motor inrush. This is usually 6 – 8 times the motor FLA. We can see on a B or C curve this amount of current would trip the breaker well under .01 seconds. This would not be enough time for a motor to start and the current to come down. But on the D curve this gives us at least 1 second which should be plenty of time for the inrush to subside. So, as you can see D curve breakers are intended of highly inductive loads like motors or transformers. The faster acting B curve is used for resistive loads which have little to no inrush and the C curves are used where only limited inductive loads are present such as lighting or control circuits. Whether you prefer circuit breakers, fuses, disconnect switches or other types of circuit protection, Automation Direct is your common sense way to buy industrial controls. If you need more assistance please see our free tech support options here. We have a vast library of other videos please click here to view all product videos. Click here to subscribe to our YouTube channel for upcoming products and solutions.
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