Treatment of common fault of relay
One, the inductive load circuit, contact wear too fast or too big ( and even spark radio interference )
When the contact wear too fast or spark greatly ( even have radio interference ), should be used in apark extinguishing circuit. Apark extinguishing circuit for relay, protection to its contact system, reducing the wear, enhance the breaking capacity, so as to ensure the safe and reliable operation of the relay is a kind of technical measures.
Relay control is the main target of various appliances electromagnetic coil and certain signal circuit, so the contact current rating are generally smaller, rarely exceeding 5A. But to achieve high sensitivity and small structure, relay contact pressure had to be made as small as possible, and the movement is very frequent, and the load is inductive, breaking condition was still very serious. Therefore, sometimes to set fire to alleviate the burden of flower circuit contact.
The so-called apark extinguishing circuit and control object is the electromagnetic coil or the contact of the relay connected in parallel to the discharge circuit. In an electromagnetic coil of the relay is de-energized when, for example JR29-45 thermal relay, the electromagnetic coil of the electromagnetic energy storage of Li2 / 2 to discharge to the discharge circuit resistance; the latter in the contacts of the relay are cut off, the current is transferred to the discharge circuit, thereby protecting the contact.
These measures are taken, if the load is contactor, attention should be paid to the possible make contactor release delayed effect.
Irrespective of the a spark-eliminating circuit, all contribute to the inhibition of electric arc or spark is generated, and the arc is generated after accelerated its quenching process. In addition, spark extinguishing circuit can inhibit contact breaking over-voltage.
AC circuit breaker is produced when the arc current zero out in nature, then the electromagnetic coil of the electromagnetic energy storage is almost zero, so the AC relay without the use of spark extinguishing circuit, it is generally only used for direct relay.
In two, the contact phenomenon of virtual connection
Relay when in use, the electric control system of the whole work, contact phenomenon of virtual connection is not frequently occur, but if it happens, it will cause a major accident. For this in a control loop due to changes of contact resistance of the electromagnetic type electric coil ends of the actual voltage is less than 220; rated control voltage caused by the accident, in the general examination is very difficult to find, unless the contact reliability test. Therefore, for a particularly important electrical control circuit of the relay, should pay attention to:
The 1 try to avoid using 12V and below the low voltage as a control voltage, the low voltage control loop, due to deficiency caused by the fault of the more common. Once in the use of JZC1-44 contactor type relay, met the above problems, and obtained the reasonable processing.
The 2 control loop using 24V as the rated control voltage, should adopt the shunt contact, in order to improve the reliability of its work.
The 3 control loop must use low voltage control, using 48V. Large capacity contactors can use an intermediate relay control, to further improve work reliability.
The 4 control loop using 220V and above voltage as the rated control voltage, high reliability.
The information above in electrical switch factory provides reference materials ( www.jiandq.com )