A) Why is a TENV motor enclosure not suitable for an explosive gas environment?
ID: 2087373 • Letter: A
Question
A) Why is a TENV motor enclosure not suitable for an explosive gas environment?
1) There are no openings in the housing, and no provisions for cooling except large cast heat fins on the sides.
2) The electrical wiring and circuit board within the enclosure are not specified for intrinsic safety.
3) There are no openings in the housing, and no provisions for cooling except large cast heat fins on the sides.
4) The enclosure cannot withstand an explosion of a specified gas or vapor inside it.
5) Items (2) and (4)
B) You are in charge of specifying a motor to run a pump in a factory that makes fruit juices. The motor is run continuously except for product changeovers, when production is converted from apple juice to orange juice and back. Temperatures in the plant are held between 15°C and 25°C. Humidity is controlled between 20% and 50%. What type of motor should you specify?
1) Washdown
2) IEEE 841-2001 Severe Duty
3) Explosion Proof
4) Totally Enclosed Fan Cooled (TEFC)
5) Totally Enclosed Nonventilated (TENV)
C) Suppose you create a Lorentz Force by passing a current through a conductor located in a magnetic field. What would happen to the Lorentz Force, if you reversed the direction of both the magnetic field and the direction of the flow of current at the same time?
The Lorentz force would double
The Lorentz force would go to zero
Nothing
The Lorentz force would switch direction
(5) None of the above.
D) Suppose you double the length L of the loop in the diagram for a DC motor. What happens to the motor torque and the back EMF?
Motor torque doubles and back EMF remains the same.
They both double.
Motor torque is cut in half while back EMF doubles
They both remain the same.
(5) Motor torque is cut in half while back EMF remains the same.
E) What is the power in watts of a DC motor operating at 500 RPM and 20 N-m torque? (Type in an integer number, rounding off your value to the nearest integer)
Explanation / Answer
a. There are no openings in the housing, and no provisions for cooling except large cast heat fins on the sides.
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