The hottest polyswitchlvrlvrl devices are

2022-08-13
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Polyswitchlvr/lvrl devices help household and professional appliances

Abstract

although the motors used in household and professional appliances are generally reliable, they are also vulnerable to mechanical overload, overheating, locked rotor, zero line fault, serious overvoltage, humidity and other damaging factors. Electrical designers have adopted various circuit protection technologies to enhance the safety protection ability and avoid fire hazards. At the same time, it also reduces the repair and replacement costs that may occur during the warranty period due to motor failure

technical comparison

the main function of many circuit protection technologies is to protect electronic circuits from damage caused by excessive current or temperature. In the past, this kind of protection used, but its performance depends on the operation of computer servo system to play the fuse or fuse. However, in today's motor applications, resettable devices such as polymer positive temperature coefficient (PPTC) devices, ceramic positive temperature coefficient (CPTC) devices and bimetal circuit breakers are better solutions. These resettable devices do not need to be replaced after failure, and can restore the circuit to normal working conditions after power failure and/or overcurrent conditions are eliminated. This resettable function can help manufacturers reduce warranty, repair and repair costs. Table 1 compares the reset functions and circuit conditions of most commonly used devices

although fuse may be one of the simplest and lowest cost solutions for motor protection, most manufacturers believe that if the resettable protection method can help prevent the motor from being damaged by overcurrent caused by electrical short circuit, over planting or customer misoperation, its cost is reasonable

pptc device is used to prevent damage caused by overcurrent surge and overheating fault at the same time, and has low resistance characteristics, and its size is also compatible with fuse solutions. Just like traditional fuses, PPTC devices can also limit the occurrence of dangerous large current under fault conditions. However, the PPTC device can reset itself after the fault condition has been eliminated and the circuit power supply has been disconnected. This method can ensure that the equipment is still in the condition of complete function, and there is no need to replace the fuse or request maintenance. CPTC devices also help to provide resettable protection functions. However, due to its relatively high operating temperature, high resistance and large size, its application may be limited. We should firmly focus on giving play to the decisive role of factors in the market to enhance the development system of financial markets. The component structure of CPTC devices is also fragile, which makes them vulnerable to impact, vibration or thermal stress caused by heating and cooling in many electrical applications. Although bimetallic sheet switches have been widely used in the field of motor protection in electrical appliances, they cannot limit the current and need additional operation to interrupt its on-off cycle. If such devices fail, it may also appear the mode of "so if you want to stabilize the market share, the barrier will close". Other disadvantages include material fatigue and the risk of contact burnout, spark splashing or welding dead closure. The possible noise or "click" and electromagnetic interference (EMI) may also cause the bimetallic circuit breaker to be incompatible with the advanced electrical control system

although the chip based solution has good results, it requires to occupy more board space and adopt multiple components, including integrated circuits, switches and sensors, resulting in design complexity and increased design costs

the PolySwitch lvr/lvrl PPTC product series of Raychem circuit protection department includes a variety of products rated at 120 VAC and 240 VAC mains, and the maximum working current at 20 ° C can reach 2 A. This series of products have passed UL certification and can be connected in parallel to increase current capacity. The low cost, resettable function and current limiting characteristics of these products make them a reliable and cost-effective protection solution, which is also applicable to intermittent and continuous motors

table 1 Comparison of resettable functions and circuit conditions of fuses and resettable circuit protection devices

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