DC Machines

In the basic construction of an electrical motor, what is the term for the stationary part?

In a DC machine, which winding carries a current that is dependent on the mechanical power produced, being small for a light load and larger for a heavier load?

A certain motor has a rated output power of 5 horsepower. What is this power expressed in watts?

A motor has an output power (Pout) of 3730 W and an input power (Pin) of 4042 W. What is its power efficiency?

A motor has a no-load speed of 1195 rpm and a full-load speed of 1150 rpm. What is its speed regulation?

What is a significant disadvantage of DC motors that leads to a need for relatively frequent maintenance?

Which type of DC motor is described as having its speed automatically adjust over a large range as the load torque varies, and is used as the starter motor in automobiles?

In the idealized linear DC machine shown in Figure 15.6, what is the formula for the voltage (eA) induced across the bar as it moves with velocity u through a magnetic field B?

For the idealized linear machine described in Example 15.2, with B = 1 T, l = 0.3 m, VT = 2 V, and RA = 0.05 ohm, what is the initial force on the bar at t = 0?

What is the primary function of the commutator and brushes in a rotating DC machine?

In the equivalent circuit of a rotating DC motor, what does the voltage EA represent?

The developed torque (Tdev) in a DC machine is given by the formula Tdev = KφIA. What does the term Kφ represent?

A DC machine has an induced armature voltage (EA1) of 145 V at a speed (n1) of 1200 rpm. If the field current remains constant, what is the induced voltage (EA2) at a new speed (n2) of 800 rpm?

In a shunt-connected DC motor, how are the field circuit and the armature circuit connected to the supply voltage?

In the power flow of a shunt-connected DC motor, what is the term for the sum of the field loss and armature loss?

According to the derived torque-speed relationship for a shunt-connected DC motor (Equation 15.27), what is the shape of the plot of developed torque (Tdev) versus speed (ωm)?

A shunt-connected DC motor is supplied by a 240 V source. The total field resistance (RF + Radj) is 24 ohm. What is the field current (IF)?

What is a primary advantage of permanent-magnet (PM) DC motors compared to motors with field windings?

In a series-connected DC motor operating below saturation, the magnetic flux (φ) is proportional to the field current (IF), which is equal to the armature current (IA). How is the developed torque (Tdev) related to the armature current (IA)?

What is a potential danger of operating a series-connected DC motor if its mechanical load is suddenly disconnected?

A series motor that is designed for use with AC sources is known as what type of motor?

What is a significant advantage of universal motors that makes them suitable for hand-held tools like drills and saws?

Which method of speed control is NOT appropriate for a shunt-connected DC motor?

What is the primary danger associated with an open field circuit in a running shunt-connected DC motor?

What is the primary function of a DC generator?

A DC generator has a no-load voltage (VNL) of 160 V and a full-load voltage (VFL) of 150 V. What is its percentage load voltage regulation?

What is a disadvantage of a separately excited DC generator that is overcome by using a shunt-connected generator?

In a compound-connected DC generator, if the magnetic field of the series coil aids the field of the shunt coil, what is the connection called?

For the separately excited DC generator in Example 15.6, the prime mover rotates the armature at 1000 rpm. The machine's magnetization curve shows EA = 280 V at 1200 rpm for a given field current. What is the no-load voltage of the generator at 1000 rpm?

A DC generator has an output power (Pout) of 44.06 kW and an armature loss (RA * IA^2) of 2.6 kW. What is its developed power (Pdev)?

In an electrical motor, the rotor and stator are typically made of what material to intensify the magnetic field?

What is the consequence of the voltage and current relationships in an ideal transformer that is also assumed for an ideal DC machine's power conversion?

In the idealized linear DC machine, when a mechanical load is applied that opposes motion, the bar slows down. What is the immediate electrical consequence of this reduction in speed?

For the DC machine in Example 15.3, with IF = 2.5 A and a speed of 800 rpm, the developed power is calculated to be 2900 W and the developed torque is 34.62 Nm. What is the armature current IA?

What is the primary reason that field windings in series DC motors are made with larger diameter wire and have smaller resistances compared to shunt motors?

In Example 15.5, a series-connected DC motor drives a load demanding a torque of 12 Nm at 1200 rpm. If the load torque increases to 24 Nm, what is the new speed of the motor, assuming ideal conditions (negligible resistance and losses)?

What is a significant disadvantage of controlling DC motor speed by inserting resistance in series with the armature?

In a separately excited DC generator, what is the primary effect on the load voltage (VL) as the load current (IL) increases, assuming constant speed and field current?

What is the term for a compound-connected DC generator where the full-load voltage is equal to the no-load voltage?

What is the chief limitation on the output power of a motor, which leads to temperature rise?

If an induction motor's torque-speed characteristic shows that its starting torque is less than the torque demanded by a hoist load, what will happen when power is applied?

In the context of the idealized linear machine operating as a generator, mechanical energy is converted into electrical energy which is delivered to what components?

For the idealized linear machine in Example 15.2, a mechanical pulling force of 2 N is applied, causing it to operate as a generator. What is the steady-state speed?

How is the developed power (Pdev) related to the developed torque (Tdev) and angular velocity (ωm) in a DC machine?

In Exercise 15.7, a shunt motor's adjustable resistance Radj is increased to 30 ohm, while VT is constant at 240 V. The original field resistance RF was 10 ohm. What is the new field current IF?

What is the key difference in the circuit configuration between a separately excited DC motor and a shunt-connected motor?

What happens to the speed of a shunt-connected DC motor when the field current is reduced by increasing the adjustable resistance Radj?

What is the purpose of the Ward Leonard system, mentioned as a historical method for obtaining variable DC voltages?

In a shunt-connected DC generator, how does the initial buildup of voltage typically occur?

A certain 50-hp DC motor operates from a 220-V DC source with losses of 3350 W under rated full-load conditions. What is the source current?