Protect motors with solid-state overloads

Journal Article · Mon Mar 01 04:00:00 EST 1993 · Hydrocarbon Processing; (United States)

OSTI ID:6388563

Forsell, K A ^[1]

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1. Furnas Electric Co., Batavia, IL (United States)

Magnetic motor starters that rely on bimetal or melting alloy overload protection do not provide the flexibility of solid-state overload technology. The point is best illustrated by the number of different overload relay trip curves that describe tripping time as a function of motor current. Solid-state overloads have a trip curve for a cold start with three-phase current, and a family of trip curves for three-phase conditions where the overload and motor are already warm. An overload relay can also be described by its single-phase trip-time curves for cold and warm initial states. All thermal overloads have single phase trip curves that are similar in shape to their three-phase curves. Slower response to phase loss for motor loads less than locked rotor is inherent in thermal overload relay design. The paper describes the power source problem; single-phase problems; thermal overloads versus solid state; and thermal NEMA overload.

• OSTI ID: 6388563
• Journal Information: Hydrocarbon Processing; (United States), Journal Name: Hydrocarbon Processing; (United States) Vol. 72:3; ISSN HYPRAX; ISSN 0018-8190
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
420200* -- Engineering-- Facilities
Equipment
& Techniques
ELECTRIC MOTORS
ELECTRONIC EQUIPMENT
ENGINES
EQUIPMENT
EQUIPMENT PROTECTION DEVICES
FUNCTIONS
MOTORS
OVERCURRENT
POWER SUPPLIES
RESPONSE FUNCTIONS
START-UP