Final answer:
The two primary protections for a motor branch circuit are overcurrent protection through circuit breakers or fuses, and grounding via a three-wire system to prevent thermal and shock hazards. A GFCI can also provide additional safety.
Step-by-step explanation:
The two basic protection requirements for a motor branch circuit are overcurrent protection and grounding. Overcurrent protection, provided by devices like circuit breakers and fuses, interrupts excessive currents to prevent thermal hazards. Grounding involves the three-wire system and ensures safety by protecting against both thermal and shock hazards, utilizing live/hot, neutral, and earth/ground wires. The grounding of the neutral wire and case of the appliance lowers the risk of electric shock by providing a safe path for current in case of a fault.
Additional safety measures include the use of a ground fault circuit interrupter (GFCI), which prevents shocks by detecting the loss of current to unintentional paths, and an isolation transformer that insulates the device being powered from the original power source.