Thiết bị & Hệ thốngCâu 254 / 521
In a motor installation, what is the primary function of the motor controller?
a.To provide short-circuit and ground-fault protection
b.To start and stop the motor by connecting and disconnecting it from the power source
c.To protect conductors from overload only
d.To serve as the required disconnecting means for maintenance
Giải thích
NEC Article 430 Part VII defines the controller as the device that starts and stops the motor by making and breaking the motor-circuit current. Short-circuit protection, overload protection, and the disconnecting means are separate required elements, though one device can sometimes serve more than one role.
Trích dẫn luật: 2023 NEC §430.81Luyện miễn phí toàn bộ 521 câu hỏi — không cần đăng ký.
Câu hỏi liên quan cùng chủ đề
- A motor nameplate reads 28 A full-load, service factor 1.0, temperature rise not marked. What is the maximum overload rating under NEC 430.32(A)(1)?
- A feeder supplies two three-phase, 460 V motors: 20 HP (FLC 27 A) and 10 HP (FLC 14 A). Per NEC 430.24, what minimum feeder conductor ampacity is required?
- A motor disconnecting means must have an ampere rating at least 115% of the motor FLC. For a 15 HP, 460 V, three-phase motor (FLC 21 A), what is the minimum disconnect ampere rating?
- A motor control circuit tapped from the load side of the motor branch-circuit protection is generally protected against overcurrent according to which NEC provision?
- A single hermetic refrigerant motor-compressor has a rated-load current of 24 A. Per NEC 440.32, what minimum branch-circuit conductor ampacity is required?
- On an air-conditioning unit nameplate, what does the 'Minimum Circuit Ampacity (MCA)' value tell the installer?
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