This is a plausible explanation. This is why fancy high power contactors will have supervisory circuits in the coil drivers to ensure that enough power is given to the coil to operate, or to turn off the coil current and report a fault if it is unable to do so.If coil burns, it is due to overcurrent, not a lower voltage. Can you measure coil current? Can you indicate coil specification by the manufacturer?
AC relays often need a higher current before the contact arm is moved to "closed" position. Then the coil current is reduced as the magnetic circuit is closed. If the arm cannot close the magnetic circuit, the coil field passes only through air and the current may stay higher, after some time burning the coil.
Average consumption at 20 °C:
- inrush 50 Hz: 550 VA; 60 Hz: 660 VA,
- sealed 50 Hz: 45 VA; 60 Hz: 55 VA, cos ϕ = 0.3.
Heat dissipation: 12…16 W.
Operating time at Uc: closing = 23…35 ms, opening = 5…15 ms.