They are six contactors. The black housing is an arc chute. It contains the arc when the tips of the contact are broken. A low voltage power a coil which creates a magnetic field to close a circuit with a larger voltage. The larger coil behind the arc chute is a blowout coil
As for what they are feeding, it could be anything. Likely, motors
I do maintenance on contactors of this type at my work daily,
Adjusting coil voltage for closing, drop-out voltages, changing pitted contacts tips, pitted arc chutes, etc...
The smaller wires coming from the contact are for numerous things. It needs to power the coil, it needs a supressor across the coil when the circuit is broken (resistor and cap) it needs also feedback so the controller knows that the tips are closed when the command to close is given. It also needs to know if a contact closes without a signal applied to the coil, which would be bad.
In my work these contactors are used on komatsu haul trucks for dynamic retarding of traction motors. When you want to brake an electric motor, you can release it from its supply voltage and its inertia ensures it is generating. An electrical load attached to the motor (through contactors) ensures the motor can be controlled to brake.
Honestly, if I had to guess, I would say this is from some piece of mobile mining equipment. Such as a B&E or P&H mining shovel or blasting drill... attached is a pic I took of a contact cabinet from a P&H drill (note the contactors)
I'm know what u have is a contactor cabinet - I don't know for what exactly..