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Calcs for supply currents to a delta connected appliance.

hertzal123
Have wired some offshore catering equipment comprising 2 heating elements and 1 lighting tx,all 3 wired in delta and designed to run at 480v,no neutral.

Have measured the current in each phase at 415v but wondered if I can find the current values on site by multiplying I x480/415.The 3 loads are dissimilar.

Otherwise,I would have to draw a vector diagram.Thanks for any help.

                                     Regards,Hz
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    Have I understood correctly, that the equipment is designed is designed for 480 volts three phase, but has been used on 415 volts for test purposes.

    If so, then when operated on the full 480 volts it will draw more current. The heating elements will draw more current in almost exact proportion to the extra voltage.

    The AVERAGE current may decrease if the elements are thermostatic as the duty cycle will be less, but the current when "on" will increase in proportion to the extra voltage.


    The lamps will also draw increased current at the higher voltage, but not in proportion. An approximation is that increasing the voltage on a tungsten lamp by say 20% will increase the current by half that much, i.e. by about 10%.


    No great accuracy may be expected without knowing the actual voltage of the nominal 415 volt supply, and the upper and lower limits of the nominal 480 volt supply.
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  • 0
    Have I understood correctly, that the equipment is designed is designed for 480 volts three phase, but has been used on 415 volts for test purposes.

    If so, then when operated on the full 480 volts it will draw more current. The heating elements will draw more current in almost exact proportion to the extra voltage.

    The AVERAGE current may decrease if the elements are thermostatic as the duty cycle will be less, but the current when "on" will increase in proportion to the extra voltage.


    The lamps will also draw increased current at the higher voltage, but not in proportion. An approximation is that increasing the voltage on a tungsten lamp by say 20% will increase the current by half that much, i.e. by about 10%.


    No great accuracy may be expected without knowing the actual voltage of the nominal 415 volt supply, and the upper and lower limits of the nominal 480 volt supply.
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