Solid state relays TTR1-PAxxx-L1D for inductive load control

In modern automation systems, circuits and switching devices are becoming increasingly important. In modern technology areas such as communication systems, consumer and industrial automation, automotive electronics, there is a gradual but clear transition from the usual switching circuits on conventional electromagnetic relays to more reliable tools such as solid state relays (SSR) everywhere.

Semiconductors are replacing mechanical switching and control devices even in circuits of powerful current loads. However, for proper operation of solid state relays, it is necessary to clearly distinguish between their use for resistive and inductive loads. In the case of using a relay to control an inductive load, it is necessary to take into account the transient processes at the moment of turning on and off the SSR. And, despite the presence of a protective circuit in all types of relays, there are still various modifications of them. Some of the solid state relays do not allow inductive loads, while others are specially adapted for them.

The current surge when controlling a powerful load of an active nature is usually eliminated by using a relay with switching at zero current (crossing "zero"). But when driving an inductive type load, a more significant current margin should be provided.

Solid state relaysTTR1-PAxxx-L1D are designed specifically to control inductive loads. Firstly, output overvoltage protection is provided by protective diodes. Second, and even more important, unlike a zero-crossing relay, switching occurs at the maximum value of the output voltage. Thus, the starting current immediately has a maximum value with a subsequent decrease in its amplitude, which ensures a minimum current overload. In addition, the SCR output (silicon controlled rectifier, or SCR thyristor) can significantly reduce the thermal resistance of the relay substrate and improve the heat sink performance.

Load power control options

However, all this does not exclude the requirement to use heatsinks and cooling fans to work with high switching currents. And you should not forget at all when choosing a relay about the need to provide the necessary current margin.

Relay switching circuit

Overall dimensions and seats

Relay modifications and switching current

Recommended operating modes