Hi,
1. How to find the maximum voltage that can be applied across zener? Should I reverse calculate the Maximum Zener Voltage from the Maximum Power Dissipation rating provided in the datasheet? If so, could you provide an example.
It's a problem of the generated heat.
The ammount of heat relates to the power dissipation
Power dissipation (of any path. LED, diode, CE of a bjt, incandescent light, ...) is the current through this path multiplied with the voltage across the two nodes.
P = V x I.
Calculation: rearranged formula above gives a simple division. You don't need an example for this.
The formula is good for a raw estimation, because V and I depend in each other.
To take this into your estimation: you may use the V-I chart of the zener and additionally draw the "P" line (hyperbolic) into the chart.
Where both lines cross this is the limit point.
But mind: maximum power dissipation is given at dedicated conditions: ambient temperature, mounting, heat spreading (via traces), air flow....
Thus, if you change one of these conditions, you also change maximum power dissipation and maximum current.
And sadly voltage drop of a zener varies with temperature.
Hint: don't go to the extremes with current and power dissipation. In a real circuit there will be limited air flow...which becomes even more limited by dirt over the years. You don't know the end users conditions in ambient temperature and orientation...
2) there are several limits:
* absolute voltage. Limited by isolation.
* absolute current. Limited by local electrical and thermal resistances, short time temperature rise....
* temperature. Short time to long time. Limits are shown in the SOA chart .... and maximum junction temperature....
Klaus