Measuring peak power for rating plate

Depends rather what the information is for. In terms of rating plates 'peak' means in use but with with all the options enables - so all the rings on a cooker for example, or a motor running at max speed. 

The term 'inrush' is normally applied to the current that flows during start up of a motor, or charging input capacitors of a power supply.  If you really mean to quantify inrush then both current and duration are relevant, and as above if the inrush is only  fraction of a cycle then as noted above, the exact instant of switch on matters - flat capacitors have highest inrush if connected to the mains at the peak voltage, while the worst time to connect an inductor with no pre-magnetisation is near a voltage zero-crossing - this would normally be the current maximum, and gives the greatest transient to sort out.


You need a scope and something to synchronize your switching electronics to the mains cycle if you want to measure this repeatedly, or you need to capture many transients and note the spread of results.


As inrush can be many times higher than normal loads, at least for larger loads, it is normal to design in some sort of inrush limit to define the worst case current. This may be as simple as a resistor that is bypassed by relay after a delay, or a series thermistor whose resistance falls as it warms up.

Also if equipment is likely to be run on an inverter, it may see the equivalent of an inrush surge on every cycle if the waveform is stepped.

Depends rather what the information is for. In terms of rating plates 'peak' means in use but with with all the options enables - so all the rings on a cooker for example, or a motor running at max speed. 

The term 'inrush' is normally applied to the current that flows during start up of a motor, or charging input capacitors of a power supply.  If you really mean to quantify inrush then both current and duration are relevant, and as above if the inrush is only  fraction of a cycle then as noted above, the exact instant of switch on matters - flat capacitors have highest inrush if connected to the mains at the peak voltage, while the worst time to connect an inductor with no pre-magnetisation is near a voltage zero-crossing - this would normally be the current maximum, and gives the greatest transient to sort out.


You need a scope and something to synchronize your switching electronics to the mains cycle if you want to measure this repeatedly, or you need to capture many transients and note the spread of results.


As inrush can be many times higher than normal loads, at least for larger loads, it is normal to design in some sort of inrush limit to define the worst case current. This may be as simple as a resistor that is bypassed by relay after a delay, or a series thermistor whose resistance falls as it warms up.

Also if equipment is likely to be run on an inverter, it may see the equivalent of an inrush surge on every cycle if the waveform is stepped.