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.
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.
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?
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?
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.
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.
How to limit inrush current of Air conditioner compressor???
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?
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?
I ask a question to them a few days ago and I still waiting for technical support
How'd you go with that question Vargas?
what is the time reaction to rush current of PTC?
How long does it takes to reach full current?
Thanks!
She completely blundered it.