What is this component?

[luiHS]

It was attached on the coil of an electromagnet. I have discovered it when removing the seal of adhesive tape from the coil, to measure the thickness of the cable and the number of turns.

This component is connected in serial with the coil. I suspect that it may be a thermistor or a varistor, which reduces electrical consumption when the coil overheats.

The coil connects to 50v and has a resistance of 4.9 ohms. So I suppose that it will have an initial consumption peak of 10 Amps, it will heat up quickly, this thermistor (or varistor) will act, increasing its resistance and reducing electrical consumption to prevent the coil from overheating, that will also reduce the electromagnetic force.

This protection could also be mainly to protect the power supply, reducing the electrical consumption after the initial peak of 10 Amps.

[Kean]

It is a PEPI FC-P2D thermal protection switch

http://pepiusa.info/model-fc-p2d/

[luiHS]

It is a PEPI FC-P2D thermal protection switch

http://pepiusa.info/model-fc-p2d/

Ok, if it is a simple thermal switch, it only prevents the coil from burning, it does not reduce the electrical consumption to protect the power supply as well.

I think I'll replace it with PWM control for better power control and protection.

[Zero999]

It is a PEPI FC-P2D thermal protection switch

http://pepiusa.info/model-fc-p2d/

Ok, if it is a simple thermal switch, it only prevents the coil from burning, it does not reduce the electrical consumption to protect the power supply as well.

I think I'll replace it with PWM control for better power control and protection.

That's a bad idea. It's also there for protection against fire.

If you want to control the power with PWM, then fine, but keep the thermal protection switch in place, in case your controller fails normally on.

[Kean]

That's a bad idea. It's also there for protection against fire.

100% correct!

It is self resetting unlike cheaper thermal fuses.  Absolutely no reason to remove this unless faulty (unlikely), in which case replace it with the same or an equivalent rated part.

[Doctorandus_P]

The coil connects to 50v and has a resistance of 4.9 ohms. So I suppose that it will have an initial consumption peak of 10 Amps, it will heat up quickly,

Indeed.
It's common to push high currents through electromagnets, but with a low duty cycle, and if for any reason the source is not turned off and this current continues for too long, the least damage will be a completely destroyed electromagnet because of the overheating.

This is not only common with electromagnets, but also with other devices containing electromagnets such as industrial servo motors. They can usually be overloaded by a factor of two to 5 for short durations, for example during acceleration.