How to eliminate the scintilla that relay produces when contact movement?
[introduction] as a result of relay of contact beat or leave those who shut is flashy the change that all can cause perceptual load, produce gas discharge phenomenon, but the electric current that contact connects relay is lesser, electric arc won’t appear between contact, but ” of discharge of scintilla of meeting occurrence “ , because inductance exists in contact circuit,this is, can appear on the inductance when disconnecting overvoltage, it and power source voltage are added on contact clearance together, the contact clearance puncture that makes firm departure was apart from and discharge.
As a result of relay of contact beat or leave those who shut is flashy the change that all can cause perceptual load, produce gas discharge phenomenon, but the electric current that contact connects relay is lesser, electric arc won’t appear between contact, but ” of discharge of scintilla of meeting occurrence “ , because inductance exists in contact circuit,this is, can appear on the inductance when disconnecting overvoltage, it and power source voltage are added on contact clearance together, the contact clearance puncture that makes firm departure was apart from and discharge.
Because energy place is restricted, can produce scintilla to discharge only, the alternant transition of the energy in the capacitance that be in and inductance is survived between contact, make show when the concealed when scintilla discharge, and become a kind of high frequency signal, deliver through high frequency radiate, lead reach the way such as distributinging capacitance and string together faze to arrive in relevant circuit, cause interference signal. Moreover scintilla discharge also can cause loss to contact, and the service life that can lower contact, electric spark is met ablation contact surface, make its surface rough cause the trouble with undesirable contact.
Circuit of RC disappear scintilla
Because this must try eliminate electric spark, practical disappear scintilla circuit is circuit of RC disappear scintilla, if plan institute is shown. It is a kind of half RC draws circuit inside casing of the dotted line in the graph, circuit of RC disappear scintilla is basic action principle is, after establishing ties R and C photograph again shunt-wound in relay the two end of contact. The energy that makes inductance medium does not pass contact and pass RC; Of the generation when it absorbs contact to disconnect only from electrification situation. In relay contact puts through the instant, as a result of RC by short circuit, do not have absorption so, it is one kind draws circuit completely outside casing of the dotted line in the graph, diode V is passed to be used up on laden RL from electrification situation when contact disconnects. One of above circuit chooses in applying actually went.
But those who want an attention is, RC parameter should choose proper, parameter basically relies on an experiment to decide, normally capacitance C can press choice of load current 1A/1μF. Its are losing polarity to should join when use diode correct, and the compression of diode V wants enough. What need points out is circuit of RC disappear scintilla should rely on relay closely contact installation, make jumper some shorter as far as possible, in order to assure the result of disappear scintilla circuit.
Be like some factory heat treatment the temperature automation system of furnace, with lukewarm control apparatus (the PID adjuster that controls output to be relay) reach auxiliary relay to come to those who control contactor connect, break control electric heat then implement. But in use because temperature appearance wave motion is big, accuse lukewarm precision to jump over Gao Jibo to move especially bigger, cause auxiliary relay movement frequent, the instant that because the electric contact of relay is in,puts through, contact admiral has the several times impact at regular job electric current, and in disconnect the instant, the electromagnetism that stores in circuit can release the form with scintilla between contact. The movement with too frequent contact causes relay the calorific, ablation of electric contact, even fusion welding, long grind a few times cannot use, can change only relay. Contactor because often flow,already passed multiple working electricity and calorific, core makes as a result of frequent movement core displacement and magnetic circuit air gap increase, and the electromagnetism noise with very large generation.
Afore-mentioned issues added to maintain workload not only, still affect production sometimes, for this this factory undertook transforming to circuit, circuit of scintilla of use RC disappear, the parameter that RC circuit chooses is: C is 100pF/1000V, of R for 1.2kΩ/1W. Receive RC component on the electric contact of relay directly, try to reduce the working electric current of contactor namely again, after taking these step, the contact service life of relay is lengthened greatly. The effect is apparent, satisfying while production asks, still reduced maintenance workload, managing upkeep costs.