An electric truck is propelled by a DC motor driven by a 110-V storage battery. The truck is required to exert a tractive effort of 220 lb at a speed of 5 mph. The overall efficiency of the motor and drive is 70 percent. What current is taken from the battery?
A25.24 A
B28.45 A
C30.22 A
D26.18 A
#2📜 EE Board October 1990
An electric motor driven conveyor belt 80 feet long is required to take 2,200 lbs of dirt, rocks, etc per minute from an excavation site and raise it 15 ft vertically. If all friction in the machinery is neglected, what hp of motor is required?
A1.5
B1.0
C2.0
D2.5
#3📜 EE Board June 1990
An electric motor is needed to drive an escalator in a department store. The escalator is 36 in wide and can accommodate two (2) riders side by side hence the loading can be considered as uniformly distributed with \(250\text{ lb/ft}\). Linear speed is 80 ft/min. The escalator angle is 38° and its lifting height is 6.5 meters. Mechanical efficiency of the system is 60%. Determine the motor size in hp.
A21.53
B22.01
C19.42
D20.84
#4📜 EE Board June 1990
An electric lift is required to raise a load of 5 tonne through a height of 30 m. One quarter of the electrical energy supplied to the lift is lost in the motor and gearing. If the time required raising the load is 27 minutes find the current taken by the motor, the supply voltage being 230 V DC.
A4.83 A
B3.42 A
C5.26 A
D6.05 A
#5📜 EE Board October 1992, EE Board April 1994
A conveyor belt of length 15-m is at 35° with respect to the ground or horizontal. It can hold 4,000 kg of ore over its total length and it travels the distance of its length in 30 seconds. Calculate the power rating of the motor in kW that drives the conveyor belt.
A10.50 kW
B11.25 kW
C13.58 kW
D12.75 kW
#6📜 EE Board October 1998
What is the work in ergs needed to raise a 10-gram weight 100-m up?
A\(4.9 \times 10^5\)
B\(98 \times 10^7\)
C\(9.8 \times 10^7\)
D\(1.96 \times 10^7\)
#7📜 EE Board October 1990
An electric lift makes 120 double journeys in a day and a load of 6 tonnes is raised to a height of 100 m in one and a half minutes. In the return journey, the cage of the lift is empty and it completes the journey in 70 seconds. The weight of the cage is 600 kg and the counter weight is 3 tonnes. Calculate the horsepower of the motor. Assume the efficiency of the lift to be 80%.
A64.24 hp
B65.75 hp
C58.70 hp
D70.43 hp
#8📜 EE Board October 1989
The power required by a plane flying at 545 km/hr is 1800 kW. Determine the average resisting force in Newtons.
A11,890
B12,420
C11,520
D12,670
#9📜 EE Board October 1990
A train weighing 1600 tons is pulled up a 2% grade by 600 hp. Train resistance is 19200 lbs. What is the speed in mph?
A22
B25
C32
D28
#10📜 EE Board April 1993
A DC series motor operates a crane at normal voltage and lifts a load of 2-tonne at 50 m/min. Determine the speed at which it will lift a load of 5-tonne.
A30 m/min
B20 m/min
C25 m/min
D28 m/min
#11📜 EE Board April 1994
How long could a 1000-hp motor be operated in the heat energy liberated by 1 cubic kilometer of ocean water when the temperature of the water is lowered by \(1^{\circ}C\) if all its heat were converted to mechanical energy?
A170 yrs
B177 yrs
C182 yrs
D188 yrs
#12📜 EE Board October 1991
Calculate the minimum rms HP required of an open type electric motor which operates at 15 hp load for 8 minutes, 10 hp load for 6 minutes, 20 hp load for 6 minutes and the motor is at rest for 12 minutes after which the cycle is repeated.
A15.00
B12.25
C10.32
D16.75
#13📜 EE Board October 1993
A transformer is designed to carry 30 times its rated current for 1 second. The length of time that a current of 20 times the rated current can be allowed to flow is
A0.67 sec
B2 sec
C1.5 sec
D2.25 sec
#14📜 EE Board October 1997
A three-phase motor draws 50 A of current at full load. What shall be the maximum inverse-time circuit breaker that maybe used for short circuit protection?
A50 A
B100 A
C125 A
D75 A
#15📜 EE Board October 1990
A synchronous condenser costs P 1000 per kVA. If a consumer is charged at P 625 per annum per kVA of maximum demand and the interest and depreciation charges are 10% on the capital invested, determine his most economical operating power factor. The power factor of the consumer load is 0.80 lagging. Assume no losses in the synchronous condenser.
A0.998
B0.988
C0.989
D0.986
#16📜 EE Board April 1982
In a group of 3 motors, one draws 15 A, the other 40 A and the third 52 A. what size of conductor in terms of ampacity must be used for the feeder circuit?
A120 A
B107 A
C134 A
D160 A
#17📜 EE Board October 1992
Given the following three-phase induction motors operating at full load. 15-hp, 220 V, 0.95 eff., 0.80 pf 25-hp, 220 V, 0.90 eff., 0.707 pf 20-hp, 220 V, 0.92 eff., 0.866 pf Determine the ampacity of the feeder circuit conductors supplying these motors.
A178.46 A
B183.93 A
C164.70 A
D205.07 A
#18📜 EE Board April 1982
A single-phase motor has rated full load current of 28 amperes. How large must be the ampacity of the fuses to be used?
A35 A
B42 A
C70 A
D84 A
#19📜 EE Board October 1998
What surge arrester's nominal rating shall you recommend to protect distribution transformer in a 34.5 kV grounded system?
A34.5 kV
B30 kV
C22 kV
D27 kV
#20📜 EE Board April 1991
An induction motor is equipped with a flywheel of moment of inertia of \(4\text{ kg-m}^2\) for driving a rolling mill. If the speed of the induction motor is 1000 rpm, what extra energy the flywheel is capable of supplying when the load comes to the motor?
