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What are the common problems of relays

                       
Update:14-11-2020
Summary:

What are the common problems of relays 1. The relay is […]

What are the common problems of relays

1. The relay is not disconnected

1) The load current is greater than the rated switching current of the SSR, which will permanently short-circuit the relay. At this time, an SSR with a larger rated current should be used.

2) Under the ambient temperature where the relay is located, poor heat dissipation for the current it bears will damage the output semiconductor devices. At this time, a larger or more effective heat sink should be used.60A three-phase meter relay

3) The line voltage transient causes the SSR output to pass through. At this time, an SSR with a higher rated voltage should be used or an additional transient protection circuit should be provided.

4) The line voltage used is higher than the rated voltage of the SSR.

2. SSR will be disconnected after cutting off the input

When the SSR should be disconnected, measure the input voltage. If the measured voltage is lower than the required release voltage, it indicates that the release voltage of the breaker is too low. The relay should be replaced. If the measured voltage is higher than the required release voltage of the SSR, it is There is a problem with the line in front of the SSR input and must be corrected.

3. The relay is not conducting

1) When the relay should be turned on, measure the input voltage. If the voltage is lower than the required operating voltage, it indicates that there is a problem with the line in front of the SSR input terminal; if the input voltage is higher than the required operating voltage, check the polarity of the power supply and if necessary Correct it.

2) Measure the input current of the SSR. If there is no current, the SSR is open and the relay is faulty; if there is a current, but it is lower than the operating value of the relay, there is a problem with the line in front of the SSR and must be corrected.

3) Check the input part of the SSR and measure the voltage across the output of the SSR. If the voltage is lower than 1V, it indicates that the circuit or load other than the relay is open and should be repaired; if there is a line voltage, the load may be short-circuited and the current is too large. The relay fails.

4. The relay works irregularly

1) Check whether all the wiring is correct, the connection is not firm or the fault is caused by incorrect.

2) Check if the input and output leads are together.

3) For very sensitive SSRs, noise can also be coupled to the input terminal and cause irregular conduction.

5. Vibration caused by AC motor or solenoid load

Due to the alternating dv/dt problem, SSR can fluctuate for half a week. At this time, it is helpful to use a buffer.