Limiting Inrush Current with NTC and PTC Themistors
Ғылым және технология
Learn how to limit inrush current using NTC and PTC thermistors in this presentation by Ametherm. Read the entire article here: www.ametherm.com/inrush-curren...
Presentation Overview: Many applications today, including industrial machinery, power tools and other high current equipment, use limiting inrush current as a major design consideration to combat the problematic effects of inrush current.
Inrush current occurs when a system powers on and experiences a spike in current. This current can be substantially higher than standard operating current. If not properly managed, it can reduce the effective operating life and impose damage to equipment. For example, inrush current could disable a cooling fan, eventually leading to total system failure.
Applications that are switched on and off quickly, such as welding equipment, present a particular concern for limiting inrush current. The limiting inrush current circuit must reset instantaneously during each power on to protect the system. This further complicates the management of inrush current.
NTC stands for Negative Temperature coefficient. The NTC thermistor provides variable resistance based on temperature. As temperature increases, the resistance drops from high to low and allows current to pass through.
PTC stands for Positive Temperature Coefficient. The PTC thermistor also provides variable resistance based on temperature. As temperature rises, resistance increases from low to high and blocks inrush current.
Typically, NTC-based limiting is used for most applications. However, there are certain scenarios that require a PTC thermistor over an NTC thermistor. These include equipment with a near-zero reset time, extreme temperature conditions, and systems that experience frequent shorts.
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Пікірлер: 11
I recently tried wiring a NTC in series with my fridge compressor in an attemp to limit inrush current on start. I measured the regular inrush current of the compressor, it was about 50A @ 127Vac. I wired a single 10Ohm NTC in series, and expected the inrush to drop about 5 times, following Ohm's Law (127Vac/10Ohm = 12.7A). However, the results were quite unexpected haha. The inrush current still measured around 48A @ 127Vac, a negligible drop, futhermore, for my surprise, the NTC literally exploded on start LOL. Somehow it still managed to keep functioning after the inrush. Steady state current is about 2A, way less than NTC max. steady current specified on datasheet of 5A.
@spelunkerd
Жыл бұрын
Compressors are a special case because they have start and run windings, with a boost of starting torque coming from the start windings. High inrush current and difficulty starting is often caused by failure of the start/run capacitor, or in smaller fridges failure of the PTC resistor that cuts the start windings out after it spools up. Failed PTC's are problematic and common causes of failure in small beer fridges, so they aren't used in bigger systems. I wasn't aware they use NTC resistors, I've never seen one. Small conventional piston compressors are often built with a permanent split capacitor design, which sometimes responds to adding a hard start kit (start cap plus potential relay) to boost starting torque, then cut out the start windings after a few seconds.
Thanks!
Will NTC work to reduce nuisance tripping of circuit breakers if a single NTC or 2x NTCs are used at the AC input to a high inrush power supply such as an LED driver with 70A 250ms inrush?
How can the tiny leads on the thermistor handle the up to 30 amp ratings of the devices? We are told to use 12 gauge wire on a 30 amp circuit in a house, but the NTC thermistor has leads the size of a guitar string and can handle up to 30 amps?
what is the time reaction to rush current of PTC?
I ask a question to them a few days ago and I still waiting for technical support
@lawbird5803
4 жыл бұрын
How'd you go with that question Vargas?
How to limit inrush current of Air conditioner compressor???
How long does it takes to reach full current?
She completely blundered it.