Panasonic ASCT1F46E manual Connection method

5. Coil	4.Twin-relay
impressed	coil
voltage	simultaneous
	operation
	5.	Continuous
		current
6. Coil	1.	Relay drive
impressed		by means of
circuit		a transistor

6

For relays which have multiple coils such as twin relay for forward-reverse operation of motor, if the coils are continuously turned on at the same time, the coil temperature may exceed the tolerance in a short time due to heat generation of each coil. Please contact us before use.

Coil heating due to continuous current applying to coil for extensive time periods will cause deterioration in insulation performance for coil.

For such circuit types, please consider the fail-safe circuit design in case of contact failure or breaking of coil.

1. Connection method

Collector connection method is the most recommendable when the relay is driven by means of a transistor.

To avoid troubles in use, the rated voltage should always be impressed on the relay in the ON time and zero voltage be done in the OFF time.

(Good) Collector connection This is the most common connection, which operation is usually stable with.

(Care) Emitter connection When the circumstances make the use of this connection unavoidable, the voltage may not be completely impressed on the relay and the transistor would not conduct completely.

(Care) Parallel connection As the power consumption of the entire circuit increases, the relay voltage should be considered.

2. Countermeasures for surge voltage of relay control transistor

If the coil current is suddenly interrupted, a sudden high voltage pulse is developed in the coil. If this voltage exceeds the breakdown voltage of the transistor, the transistor will be degraded, and this will lead to damage. It is absolutely necessary to connect a diode in the circuit as a means of preventing damage from the counter emf. In case of DC relay, connection of Diode is effective. As suitable ratings for this diode, the average rectified current should be equivalent to the coil current, and the reverse blocking voltage should be about 3 times the value of the power source voltage. Connection of a diode is an excellent way to prevent voltage surges, but there will be a considerable time delay when the relay is open. If you need to reduce this time delay you can connect between the transistor's Collector and Emitter with a Zener diode that will make the Zener voltage somewhat higher than the supply voltage.

Diode

Take care of Area of Safe Operation (ASO).