Connecting inductive load directly

Hello,

I am using ET200SP system to control a system consisting of solenoid valves (rated 24VDC/0.25A).

For that purpose I am using the hi-speed DQ module for the PWM valves, and a standard DQ module for the solenoid valves that require only occasional actuation.

I saw in the hardware manual of the modules that there is a reference for the switching frequency of inductive loads, meaning I can connect them directly.

Up until now i always used coil relays or SSR between the PLC modules and the valve as a "good practice" and to protect the PLC modules.

Can anyone tell from experience if this is necessary, given the highly rated S7-1500 series?

I guess that with the S7-1200 i would not risk it.

If indeed connecting directly, is it truly necessary to use a snubber diode, or the internal circuitry of the module includes protection?

Thank you,

Yoav

Hello, 

Documentation said : 

Limitation of inductive shutdown voltage to Typ. L+ (-50 V)

max 2Hz switching freq