In the Japanese culture taking power naps during work is common. It is called "Inemuri", which means "Sleeping while present".
I take power naps on most days. I am an early riser and on most days after a 3am start I try to take a power nap. My usual times of power nap are 6-7am. Some days its 2-3pm if I get time. When I take a power nap during late evenings then it leaves me groggy.
Power naps help you recharge & make up for lost sleep. Even a 30 min power nap is good enough. I have seen people take a 15 min power nap as well.
In India taking a power nap at your work desk is not common. I have seen people who are sick sleeping in the sick room.
What about you?
