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Jan 25 '21 at 10:03 comment added Amogh Jain Thank you once again! I think I undestand relays a lot better now and will perform the field tests with 0.75hp motor. We chose a 3hp relay to ensure we are not bottlenecked in case some of our customers have a 1 or even 1.5 hp motor. Thanks!
Jan 25 '21 at 3:54 comment added vu2nan You are most welcome, Amogh! By 'relay with 2 contacts' I meant one with 2 sets of 'NO' or 'NC' contacts (one to switch the line and the other the neutral). A 'double throw' relay is one with 'change-over' contacts. A 'dual coil' relay only refers to one with a 'set' and a 'reset' coil. The motor rating is mentioned as 0.75 HP in the question but 1.5 HP in the comment. Please ensure that the relay ratings are not exceeded.
Jan 25 '21 at 1:25 comment added Amogh Jain Thank you so much for providing the fuse ratings !!! I wasnt quite sure of those! The relay that I have chosen is HFE10 has max load of 50A and can provide inrush current for motor upto 1-2hp(datasheet says 3hp, but our max load is expected to be 1.5hp), which seems sufficient for my use case. Lastly, I was wondering what you meant 'relay with 2 contacts'? Does it mean 'Double Throw' relay ? Can 'Dual Coil' relay be considered a relay with 2 contacts?
Jan 24 '21 at 11:34 comment added vu2nan Hi Amogh, In a latch relay, 'NO' & 'NC' contacts wouldn't make a difference except for the coil required to be energised to close the contact. You may use a relay with 5V coils and avoid the SMPS. The cable should be rated at 125%, slow blow fuse at 175% and MCB (if used) at 250% of motor full load current. A second relay for the neutral is not a must. Instead you may look for a relay with 2 contacts.
Jan 24 '21 at 10:09 comment added Amogh Jain I am developing this project with final cost being a real concern! I was able to find another relay with similar characteristics but with NO contacts. As it stands, Relay is the most expensive part with costs being around $3 with MOQ as 1, and $2.4 with 10 units. In my initial research I wasnt able to find a single contactor for less than $15 CAD. Should I just add another relay on neutral line as well? I apologize for I didnt tell that I was using esp32 @ 3.3 volts to drive the unit and a SMPS will boost externally supplied 5v to 12V, in addition to a slow blow fuse on line side on AC line.
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Jan 13 '21 at 12:11 history answered vu2nan CC BY-SA 4.0