Electric motors present a large inrush (starting) current at the instant of switch-on. At standstill the motor's back-EMF is zero, so only the low winding resistance limits the current, allowing it to surge to typically 5 to 8 times the full-load running current for a short interval until the motor accelerates and back-EMF builds up.

When a relay switches this motor, its contacts must carry that surge every single time the motor starts:

• If the contact rating equals only the running current, the repeated inrush overloads the contacts. This causes excessive arcing, pitting, and eventually the contacts may weld shut or burn open — a frequent cause of relay failure in motor circuits.
• Therefore the relay contact rating must exceed the motor's peak starting current, ensuring the contacts survive the inrush and make/break reliably over many operations.

The suggestion to match only the running current ignores the inrush entirely and is the very mistake that leads to contact failure. The options that fixate solely on coil voltage or minimum coil voltage confuse two separate aspects of a relay: the coil rating governs how the relay is energised (the control side), whereas the contact rating governs how much load current can safely be switched (the power side). For a high-inrush motor load, it is the contact current-handling capacity that is critical.