Ashida ADR241B, Instruction Manual

Page: 105 / 272

ADR241B
Doc ID : ADR241B-DO_IM_01
Ref ID : ADR241B/IM/PLF
Rev No. : 06
Page No. : 105 of 272
Where
Irms : RMS current corresponding to the largest phase current
Ith> : Thermal Trip or Full load current rating.
k : constant is settable.
A : Initial thermal state. If the initial thermal state is 30% then A =0.3
The calculation of the thermal state is given by the following formula:
Θi+1 = (Irms /k*Ith>) ² · [1 – exp (-t/Te)] + Θi · exp (-t/Te)
When thermal state reached the “Thermal Alarm” settings then relay generates Thermal
ALARM signal and assigned LED will Glow, simultaneously relay assigned to Thermal Alarm
will be operated. Similarly, if Thermal State reached at thermal capacity, then Relay
generates Thermal Trip Signal and operates relay assigned to Thermal Trip and assigned
LED will glow.