(5) DC Machine Efficiency

How do friction and windage cause mechanical losses in a rotating dc machine?

Friction occurs in bearings and brush/commutator friction, windage is air resistance when armature rotates.

How do eddy currents and hysteresis cause magnetic losses in a rotating dc machine?

Eddy currents induced in core material of armature + poles, resulting in heat losses. Coercive (hysteresis) force required to alternate magnetic fields uses energy, resulting in heat losses

How is power input, power output and losses calculated in a rotating dc machine from speed, torque, voltage and amperage?

(example is gen., swap first two steps formulas for motor) Calculate power in, then power out, then losses

What is the efficiency formula for DC Machines?

η% = efficiency in percentage
Pout = output power (W)
Pin = input power (W)

What is formula for copper losses?

P = power (W)
I = current (A)
R = resistance (Ω)