Panasonic ASCT1F46E manual Residual Coil Voltage, Connection to the next stage through collector

6.Coil impressed circuit

1.Relay drive by means of a transistor

2.Relay drive by means of

SCR

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6. Residual Coil Voltage

In switching applications where a semiconductor (transistor, UJT, etc.) is connected to the coil, a residual voltage is retained at the relay coil which may cause incomplete restoration and faulty operation. Using of DC coils may cause incomplete restoration or reduction in contact pressure and vibration resistance, because its drop-out voltage is lower than that of AC coil (10% or more of the rated voltage) also because there is a tendency to increase the life by lowering the drop-out voltage.

When the signal from the transistor's collector is taken and used to drive another circuit as shown in the figure as follows, a minute dark current flows to the relay even if the transistor is off. This may also cause the problems described above.

Connection to the next stage through collector

1. Ordinary drive method

For SCR drive, it is necessary to take particular care with regard to gate sensitivity and erroneous operation due to noise.

IGT : There is no problem even with more than 3 times the rated current.

RGK : 1K ohms must be connected.

RC : This is for prevention of switching error due to a

sudden rise in the power source or to noise.

2. Cautions regarding ON/OFF control circuits

(when used for temperature control circuits or similar one)

Care must be taken because the electrical life suffers extreme shortening when the relay contacts close simultaneously with an AC single phase power source.

1.When the relay is turned ON and OFF using a SCR, the SCR serves as a half wave power source as it is, and there are ample cases where the SCR is easily restored.

2.In this manner the relay operation and restoration timing are easily synchronized with the power source frequency, and the timing of the load switching also is easily synchronized.

3.In case of the load for temperature control whose load is a high current load such as a heater, some relays switch only peak values and some other relays switch only zero phase values as a phenomenon of this type of control. (Depending upon the sensitivity and response speed of the relay)

4.Accordingly, it causes either an extremely long life or an extremely short life resulting in wide variation. So, it is necessary to take care with the initial device quality check.