App mid
1 million amper is equal to
0.001 amp
There are many different ways to compare the economic factors of upgrading an electric motor. The following is a list of payback numbers for a motor upgrade in a conveyor system. If only payback is considered, the best option for the upgrade would be
0.7 years
The current drawn by 120 V, infrared heat lamp that has a resistance of 72 ohms is
1.67 A
A transformer has the primary energized at 240 V and the output is 120 V. If there is a 20 amp flowing in the secondary circuit the current flowing in the primary circuit will be
10 A
If your toaster is rated at 1200 boats and 120 V the current will be
10 A
A three phase, let's go motor draws 50 KW at 240 V. The power factor is determined to be 0.84 in the efficiency of the motor is 0.90. The current flowing in one of three on the ground and conductors supplying the motor is approximately
143 A
Read a resistance type heating element in a water heater is rated for 3500 W and operates at 240 bucks. The resistance of the heating element is
16.46 ohms
Assume that the total current of the circuit is 2.5 A, the voltage drop across the 8 ohm resistor, R1, of the circuit is
20 volts
A lamp draws 2.4 A when connected to a 125 supply, the power drawn by the lamp will be
300 W
The synchronous speed of a two pole, three phase, induction motor, with 60 HZ suppliers
3600 RPM
The power drawn by 240 V, resistance heater that is drawing 15 A is
3600 W
A single phase transformer has a rating of 212.5 kVA. If the output voltage of a transformer is 240 V, transformers full load current writing on the secondary will be
469 A
An 8 ohm, 16 ohm, and 24 ohm resistor are connected in series and energized at 120 V, with 2.5 A going to the resistor R1. The total resistance of the circuit is
48 ohms
The resistance of a circuit Which will permit for amps to flow with a source of 208 V is
52 ohms
A circuit has two 18 ohm resistors in parallel. The total resistance in the circuit is
9
The shaft of a three phase induction motor will
Always be slower than the RPM of the magnetic field
The single phase induction motor that has the highest rated starting torque is the
Capacitor start, capacitor run, (dual capacitor) motor
The motor, from the list below that cannot operate continuously at variable speeds by controlling the supply voltage to the motor is the
Capacitor start, induction run motor
When I do all voltage, three phase, induction motor is operated at a higher voltage, the motor will
Draw less current
The E in ohms law and the power formula stands voltage engineers and technicians also for the E as
Electro motive force
When comparing motor starter current and current drawn after reaches its nameplate speed, the starting current will be approximately
Five times the running full load current
If the north pole or the magnet is on the left in the south pole is on the right, the magnetic flux lines on the outside of the magnet will point
From north to south
The conductor of an electric system that is connected to the earth is
Grounded conductor
To have an induction motor operate with us few losses as possible, motor manufacturers
Have a little airgap as possible between the stator in the rotor
If a capacitor start induction run motor that is rated for operation at 50Hz, is actually with a 60Hz supply, the motor will
Have a shaft speed that is greater than that which is listed on the nameplate
If a three phase induction motor, that is rated for operation at 50 HZ, is actually operated supplied with a 60 HD supply, the motor will
Have a shaft speed those greater than which it is listed on the nameplate
A core of an electromagnet Will become magnetized, as the molecules within the core alone themselves, with the lines of magnetic flux. When the coil is supplied with an alternating current power source, the molecules must continually rely themselves as the flux lines reversed back-and-forth with each her cycle. This causes power loss in the electromagnet due to
Hysteresis
A DC motor will draw more current at
Locked rotor
A Three phase, induction motor will draw more current at
Locked rotor
A capacitor start induction motor will draw more current at
Locked rotor
Reduced voltage starting is an excellent way to limit starting current, but cannot be used when the
Motor is powering a hard starting load
As the output frequency from a variable frequency drive decease the
Motor shaft will slow down
Electrical current flows in the secondary circuit of a transformer, when current flows in the primary circuits due to a process called
Mutual induction
The NEC table full of current of a DC motor will be found in
NEC table 430.247
Current used to size the motor overload protection device for a single phase induction motor is the
Nameplate current
The motor housing that is commonly used in environments where rain could land on the motor housing but should never be located in a location where dust could often collect on the motor is identified by the enclosure designation is
ODP (open drop proof)
The electrical meter that requires a circuit to be disconnected before any reading can be taken is the
Ohmmeter
One hertz is
One cycle per second
The permanent split capacitor motor is also know as the
PSC motor
The moving part of an induction motor, that is often called the squirl cage
Rotor
The moving part of the induction motor that is often called the squirrel cage is the
Rotor
With a load is applied to a three phase squirrel cage induction motor the
Rotor slip increases
For a wound rotor motor, the conductors that are connected to the brushes to extend to the ternal bank of registers are called
Secondary conductors
The type of DC motor that varies in speed as the load torque changes, but can develop very high torque low speed is a
Series feild DC motor
The type of DC motor that should not be belt driven, because if the belt breaks and there is no load on the shaft the RPM is likely to increase to the point of self-destruction is
Series field DC motor
The type of DC motor that will also operate on AC power is called a universal motor is a
Series wound DC motor
The single phase induction motor that cannot be reversed is the
Shaded pole motor
As the number of Poles the motor has increases
Shaft speed decreases
The type of DC motor that is running a white load or no load Could result in a runaway shaft if the fuel winding becomes disconnected is a
Shunt field DC motor
In electrical circuit requires a
Source of power and a path for current to flow
The part of the induction motor, that contains the windings, that make the moving magnetic field, is often called the
Stator
The purpose of the motor controller is to
Stop and start the motor
A 3 phase induction motor is operating at full speed, powering a load and suddenly the AC current supply is removed from the circuit and DC current is applied to the stator winding of the motor. The rotor of the motor will
Stop quickly depending on the level of DC current in the stator winding
If the north pole of one permanent magnet is in close proximity with the south pole and another permanent magnet
The magnets will attract each other
Examine NEC section 430.32C. This section can be applied when
The motor overload Protective device is not sufficient to allow the motor to start
In order to keep the current to the motor from increasing excessively, as the frequency is decreased below 60Hz
The output to the motor is decreased
The moving part of the induction motor that is often called the squirrel cage is
The rotor
The electrical system that can provide both three phase power as well as single phase power at 120 and 240 V is
Three phase 4 wire Delta system
The strength of an electromagnet Can be increased significantly by
Using high resistant wire to four more coils
It is permitted to apply the provisions 430.50C1 exception 2
With the branch circuit short circuit, ground fault, protective device sized using 430.52 exception one is not sufficient to allow the motor to start
Which of the following is not a method of reduced-voltage (soft-starting) an induction motor?
Wound motor
A three phase, induction motor works on the principle that
A moving magnet field induces current and two loops or coils of wire that make up the rotor
The synchronous speed of a 6 pole 3 phase induction motor with 60Hz supply is
1,200 rpm
The synchronous speed of a four pole single phase induction motor with 60 Hz supply is
1,800 rpm
Two resistors are connected in parallel, R1 has the value of 20 ohms and R2 has a value of 60 ohms. The voltage across R2 is
120 V
The voltage which produces a flow of 5 A in a circuit with resistance of 25 0HMS is
125 V
I main feeder wire from The main service of a building to an electrical panel consist of two conductors which are 100 feet in line for total of 200 feet of conductor. The total resistance for the 200 foot ran conductor is 0.015 ohms. If the current flow on the conductor is 160 ampers, and the voltage drop would be
2.40 V
Are you single phase 3 wire logical system with 120 V between wire a in the neutral, and 120 V between wire be in the neutral. Between wire and wire be there will be
240 V
A single phase transformer has a secondary full load current of 104.17 A and the secondary output voltage is 240 V. The rating of the transformer in the kilo volt amp is
25 kVA
A machine is required to turn at approximately 1160rpm. If the drive motor turns at 1740 and has a 2 inch pulley the pulley needed for the machine is
3 inch
The synchronous speed of a two pole, three phase, induction motor, with a 60 HZ supply is
3600 RPM
A three phase, electric motor circuit originates with a fusible disconnect switch containing to element time delay fuses. The circuit wires are copper with 75°C terminations. The motor starter that controls the motor contains current sensing overload sensors. The following information is found on the motor nameplate three phase, 60 HZ, 50 HP, 480 V, 60 amp full load current design B, service factor 1.15, blah blah blah
4 AWG
A transformer has a primary winding energize at 480 V in the secondary I'll put his 120 V. Returns ratio of the transformer is
4/1
When comparing motor startup current and current drawn after it reaches nameplate speed, the starting current will be approximately
5x the running full load current
Single phase 3 wire, 120/240 V electrical system show in a diagram. A 16 amp load is connected between leg A and a neutral, A 10 amp load is connected between leg B and the neutral. The current flowing on the neutral conductor is
6 A
When comparing premium efficiency induction motors to non high efficiency motors, the premium efficiency motors will have
A higher starting current
For most conditions, NEC Table full load current is used to size all of the following components except
A motor overload device
By a process called self induction
A reverse voltage is created in a coil to oppose the supply voltage
A single phase induction motor is different than a three phase induction motor because the single phase more generally has
A starting or auxiliary winding
A single phase induction motor is different than a three phase induction motor because the single phase motor generally has
A starting or auxiliary winding
The shaft of a capacitor start induction motor will
Always be slower than the rpm of the load that is being applied
The shaft of a capacitor start, capacitor run motor will
Always be slower than the rpm of the magnetic field
If the chef speed of a DC motor at a faster rate through the same amount of flux created by the field the
Amount of voltage induced into the armature will increase
A DC excited synchronous motor, when starting functions as
An induction motor
The magnetic flux lies around the conductor that form due to conventional current flow
And circle the conductor with the lines coming From the back, under the wire and pointing out the page
If the current supplied to the field of a DC motor decreases the
Armature Will speed up
When a load is applied to the shaft of a DC motor, the
Armature speed is reduced
If a device has a mechanical timing mechanism that is operated by a electric motor, the type of motor that should be used for this application is
Asynchronous motor
The locked rotor it is located where
At the beginning of the graph and has the most current correlated
The purpose of a transformer is to
Change voltage
The brushes of a DC motor, right against the
Commutator
The starting winding used in the induction start induction run motor causes the
Current in the running windings to peak before the current in the starting winding
The capacitor used in the capacitor start induction motor causes the
Current in the starting windings to peak before the current in the running winding
The single phase induction motor that can be controlled to a wide range of speeds by varying the supply voltage is the
Permanent split capacitor (PSC)
The input of a transformer is connected to the electrical supply and is constructed by windings or wrappings a conductor around the steel core. This input winding is commonly referred to as the transformers
Primary winding
The main purpose of the ground fault, short circuit, protective device is to
Protect the conductors and equipment from excessive currents and dangerous temperatures
In the direction of rotation of the shaft of a three phase, induction motor can be reversed by
Reversing any two of the three power leads supplying the motor
When conventional current Flow is used, the rule to determine the direction of magnetic flux, current flow in motion of a wire is the
Right handed rule