positive voltage regulator that can work maximum with 24 volt I have a
Where I can buy a positive voltage regulator that can work with 50 volt
Using a linear regulator for 50V in and 5V out is a bad idea, since you will get a loss of 88.9% min.
For every 111mW of usefull power (=22mA out), you will waste 889mW.
Loss always equate to heat and that you'll have to get rid of.
With a switching regulator, you'll get at loss of somewhere between 5% and 30%, depending on method and design of the regulator.
If you need to stay linear, you can either drop some of the power in a resistor (or lamp), or make a regulator out of discreet components.
What (mac.) output current do you need?
How large a ripple-voltage can you tolerate?
also I search after a driver that can control a motor that work with 110 volt and 50 ampere
the system work with 50 [hz]
I'm afraid that you'll have to device one yourself to keep it from being really expensive.
If a phase angle control will be adequate (depends on the motor type and the regulation range), it should be doable as long as you get TRIACs that can handle the current (with some overhead).
Please provide the missing information if you want a better answer.