Question 1 of 15
What does OCPD stand for in the context of motor protection?
OCPD stands for Over Current Protection Device, which protects against short circuits and ground faults.
Question 2 of 15
According to NEC, what is the primary function of OCPDs in a motor branch circuit?
OCPDs primarily protect against short circuits and ground faults in the motor branch circuit.
Question 3 of 15
What percentage of the motor's full-load current (FLC) is typically used to size OCPDs?
OCPDs are generally sized between 150% and 300% of the motor's FLC.
Question 4 of 15
Which NEC table is primarily used to determine the maximum rating or setting for motor branch-circuit short-circuit and ground-fault protective devices?
NEC Table 430.52(C)(1) provides the maximum ratings or settings for motor branch circuit protection devices.
Question 5 of 15
What is the typical percentage of FLC used for sizing a non-time-delay fuse for a standard AC motor?
Non-time-delay fuses are typically sized at 300% of the motor's FLC.
Question 6 of 15
For a time-delay fuse, what percentage of the motor's FLC is typically used for sizing?
Time-delay fuses are typically sized at 175% of the motor's FLC.
Question 7 of 15
What percentage of FLC is used to size an instantaneous-trip circuit breaker for a typical AC motor?
Instantaneous-trip circuit breakers are typically sized at 800% of the motor's FLC.
Question 8 of 15
What is the maximum setting allowed by the NEC for an inverse-time circuit breaker protecting a typical AC motor?
Inverse-time circuit breakers are typically sized at 250% of the motor's FLC.
Question 9 of 15
Which NEC table is used to find the FLC of a single-phase motor?
Table 430.248 is used to find the full-load current for single-phase motors.
Question 10 of 15
When sizing OCPDs, should you use the motor's nameplate FLA or the FLC from the NEC tables?
Always refer to the NEC tables for FLC when sizing OCPDs, not the motor's nameplate.
Question 11 of 15
What does FLC stand for?
FLC stands for Full Load Current, which is the current the motor draws under normal operating conditions.
Question 12 of 15
According to NEC 240.6(A), what can be done if the calculated OCPD size doesn't match a standard rating?
NEC 240.6(A) allows for using the next higher standard rating if the calculated value doesn't match a standard OCPD size.
Question 13 of 15
What is the primary difference in protection provided by OCPDs and overload protective devices?
OCPDs protect against short circuits and ground faults, while overload devices protect against overload conditions.
Question 14 of 15
If an inverse-time circuit breaker trips during motor starting, what can be done according to NEC 430.52(C)(1) Exception No. 1?
NEC 430.52(C)(1) Exception No. 1 allows increasing the protection device size up to 400% of the FLC for inverse time circuit breakers if tripping occurs during motor starting.
Question 15 of 15
What NEC Article provides guidelines for sizing OCPDs for motor branch circuits?
NEC Article 430 provides guidelines for sizing OCPDs for motor branch circuits.
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