Dave's Museum CD set has the HP-46 Operating Guide on it. I'd recommend getting a set because you never know when you'll get an old calculator or peripheral without documentation, and this set has nearly everything! Anyway, here's what it says about power:
"Before connecting the power cord to the back of your calculator, check the setting of the voltage selector card in the power module. The number visible indicates which voltage is set. The HP-46 operates on power line voltages of 100, 120, 220 and 240 volts ac, with a power line frequency of between 48 and 66 Hz. If the card is set to the available power line voltage, you may skip the next step and go to step three.
"CAUTION: THE HP-46 CAN BE DAMAGED IF IT IS SWITCHED ON WHEN NOT SET TO THE CORRECT LINE VOLTAGE.
"To reset the voltage selector card: Slide the plastic window on the power module completely to the left; then remove the fuse by moving the FUSE PULL lever to the left. Pry the voltage selector card out (use a pointed tool such as a ball-point pen) and re-insert it so that the number representing the available line voltage is readable. Move the FUSE PULL lever to the right and insert the correct fuse for the new line voltage setting. Then slide the plastic window back to the right.
"NOTE: For 100 and 120 volts ac operation, use a 1/2 A. fuse. For 220 and 240 volts ac operation, use a 1/4 A. fuse.
"Plug the power cord into the back of the calculator and into a suitable power outlet. The calculator requires a maximum of 40 voltamps.
"Turn your calculator ON by pressing the LINE switch. Each time the HP-46 is switched-on, the word CLEAR is printed (provided PRT OFF is released). To switch-off the calculator, merely press LINE again so that OFF is visible.
"Your calculator meets current NEMA (National Electrical Manufacturers' Association) grounding standards provided that a 3-conductor power cord is used to supply power to the calculator from a suitably grounded outlet."
The manual also mentions that there were five different power cords (with different plugs) made for this calculator. The cord included was supposed to match the outlets in the area in which the calculator was sold. If the cord you have doesn't fit your outlets, the manual says to contact your nearest HP Sales and Service Office. However, I'd say the chances of them stocking HP-46 power cords at this late date are slim, so I hope you already have the right cord.
Wayne