A 75 HP, 3-phase, synchronous motor is connected to a 230-volt line. The motor is to be operated at 80% power factor. The motor nameplate lists a full load current of 185 amperes, a temperature rise of 40°C, and a code letter A. The conductors are to be made of copper and have type THHN insulation. The short-circuit protective device is to be an inverse time circuit breaker. Determine the conductor size, overload heater size, circuit breaker size, and the minimum size NEMA and IEC starters. The starter contains current transformers with a ratio of 300:5 to reduce current to the overload heater O Conductor size 250KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA5)(IEC R or S) Conductor size 250KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA6)(IEC R or S) Conductor size 350KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA5)(IEC R or S) Conductor size 300KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA5)(IEC R or S)
A 75 HP, 3-phase, synchronous motor is connected to a 230-volt line. The motor is to be operated at 80% power factor. The motor nameplate lists a full load current of 185 amperes, a temperature rise of 40°C, and a code letter A. The conductors are to be made of copper and have type THHN insulation. The short-circuit protective device is to be an inverse time circuit breaker. Determine the conductor size, overload heater size, circuit breaker size, and the minimum size NEMA and IEC starters. The starter contains current transformers with a ratio of 300:5 to reduce current to the overload heater O Conductor size 250KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA5)(IEC R or S) Conductor size 250KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA6)(IEC R or S) Conductor size 350KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA5)(IEC R or S) Conductor size 300KCMIL, Overload size X42 Inverse time circuit breaker 500A Starter size(NEMA5)(IEC R or S)
Chapter14: Phase Failure Relays
Section: Chapter Questions
Problem 1SQ: What is the purpose of phase failure relays?
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Question

Transcribed Image Text:9
A 75 HP, 3-phase, synchronous motor is
connected to a 230-volt line. The motor
is to be operated at 80% power factor. The
motor nameplate lists a full load current of
185 amperes, a temperature rise of 40°C, and
a code letter A. The conductors are to be
made of copper and have type THHN
insulation. The short-circuit protective
device is to be an inverse time circuit
breaker. Determine the conductor size,
overload heater size, circuit breaker size, and
the minimum size NEMA and IEC starters. The
starter contains current transformers with a
ratio of 300:5 to reduce current to the
overload heater
O Conductor size 250KCMIL, Overload size X42
Inverse time circuit breaker 500A Starter
size(NEMA5)(IEC R or S)
O Conductor size 250KCMIL, Overload size X42
Inverse time circuit breaker 500A Starter
size(NEMA6)(IEC R or S)
O Conductor size 350KCMIL, Overload size X42
Inverse time circuit breaker 500A Starter
size(NEMA5)(IEC R or S)
O Conductor size 300KCMIL, Overload size X42
Inverse time circuit breaker 500A Starter
size(NEMA5)(IEC R or S)
+
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