Commonly used in the small home appliance motor protection over the design process can be designed PPTC model,of course there are exceptions,multifunction soybean milk maker of motor protection both of the commonness of small home appliance motor stalling protection problem,also has its characteristics,motor protection with multifunction soybean milk maker under the special solutions to describe it.General multifunctional soybean milk maker is made up of Y series motor and electric heating system integration products together,the whole machine process by the microcomputer automatic control system,formed a relatively complex system.Multifunction soybean milk maker from the analysis on structure,mainly has the nose,body,motor,coupling,the lid and the cup body,knife shaft,control circuit,LCD display,etc.In the soybean milk maker has a temperature sensor,the temperature of the heater heating cup used in the detection of the body when the water temperature reaches electric vehicle motor MCU set temperature (assuming about 80 ℃),MCU starter motor start grinding soybean milk.General multifunctional soymilk preheating,beating,the juice,such as full automatic process,are all controlled by MCU,the corresponding driving triode,again group composed of multiple relay relay circuit switching.The motor in the multifunction soybean milk maker is a very important component,its use security issues directly affect the reliability of the soybean milk maker.
Because when using multifunctional soybean milk maker,soybean milk maker often happens when making juice locked-rotor,locked-rotor refers to the cup body of the motor of the items will be fixed motor bearing rotation,when the voltage is added to the ends of the motor,then the current is blocked,the general motors are not allowed to happen locked-rotor,because the temperature of the motor coil motor blocked in turn will sharply rise,more than the highest temperature of coil temperature,after a long will burn out motor,which increase the inconvenience of consumers,producers also increases the maintenance costs.So add the motor protection device is indispensable in the soybean milk maker,and can automatically recover after locked-rotor eliminate protection,so choose TE connectivity company recoverable PPTC is a good solution.See from the data of the soybean milk maker locked-rotor current only three times as many current in normal working conditions,consider the highest temperature of 85 degrees and the lowest temperature 0 degrees,grinding soya-bean milk for a long time,want to be in like half an hour to maintain the normal work of the motor,so the design of the motor protection,is very complicated,because it is hard to meet the requirements of PPTC time move fast,because when locked-rotor current in normal working conditions and current ratio,the greater the protect time faster,PPTC PPTC selection are more easily.Now at 0 c temperatures of 1.6 ~ 1.7 A locked rotor wholesalemotor.blogspot.com electrical flow,LVR100 protection will be very long,far cannot satisfy at 0 c temperature time 150 s protection requirements.That how to realize the multifunction soybean milk maker motor protection problem?
TE connectivity company developed a use as PPTC and power resistance using thermal coupled way connected components to realize the rapid and locked-rotor multifunction soybean milk maker motor
protection.This example USES the LVR100 and 1 ohm / 3 w power resistance thermal coupled
components,let the power for good thermal contact resistance and LVR100,the purpose is to make the
power resistance can be blocked when heat LVR100 makes it faster protection,the power of 1 ohm
resistor is selected in order to reduce the impact on the dc motor.First select LVR100 Rmin ohm
resistor and 1/3 w power resistance thermal coupled components for 0 c temperature squeezed fruit
motor stalling protection time.Secondly selecting typical value resistor LVR100 integrated components
and power resistance,to 0 c/c temperature 25 squeezed fruit motor stalling protection time,and then select R1max 0.58 ohm resistor LVR100 resistance and power integration components for grinding soybean milk hold trials of the experimental results show that the component can be in a complete grinding not false action in the process of soybean milk.With mentioned above PPTC design process can be used in the design of multi-function held in soybean milk maker motor protection,but this is often can choose PPTC model difficult problems,that is to say,multifunction soybean milk maker of motor protection design more complex than ordinary small home appliance motor protection,figure 4 for grinding soybean milk PCB ambient temperature and motor shell temperature of the measured figure,visible control circuit PCB PPTC surroundings the highest temperature can reach 85 c.As a result of the soybean milk maker PPTC top temperature of 85 degrees will be higher than ordinary small home appliance is highest temperature requirements,both to the maximum of 85 degrees to work back to work,and ensure that the lowest temperature of 0 degrees blocked the protection of the current situation in a timely manner,the corresponding increase the design difficulty.Expounds the following specific such multifunction 8500w gasoline generator soybean milk maker motor stalling protection design.
connected,make them ac electric motorsbecome smooth electrical grounding network,between the grounding method for common ground.Common grounding is currently the most widely used.Three,one-point earthing:each system grounding line connects to ground strap the same point or the same metal plane,one-point earthing method can solve the potential ac alternators 220v problems such as ground wire of each system,so can reduce the degree of interference between each system,especially the electric motors price 50 hz power frequency signal to eliminate interference on the system basically,so a little grounding method is widely used in engineering.A little grounding eliminates common impedance coupling and low frequency interference caused by ground loop.Can work well in more than 1 MHZ and frequency,when the size of the whole system is small (maximum size less than 20,l/l for jamming signal wavelength) can be applied to the 10 MHZ.
