Advantage of DC Shunt motors:

It has a constant speed independent of the load. It is best use in commercial application that uses low starting torque.

Speed can be easily controlled with inserting a series resistance with the armature

DC SHUNT MOTOR SELF EXCITED

1. A shunt motor draws 6KW from a 240 V line. If the field resistance is 100Ω, find Ia, If and IL.

Given: Po = 6KW

VL = 240V

Required: If IL & Ia

DC SHUNT MOTOR SELF EXCITED

2. A shunt motor connected to a 120V line at a speed of 1200RPM when the armature current is 20A. The armature resistance is 0.05Ω. Assuming constant field flux, What is the speed when the armature current is 60A.

Given: VL = 120V Required: n2

n1 = 1200RPM Φ Constant

Ra = 0.05Ω

Ia = 20 A

DC SHUNT MOTOR SELF EXCITED

3. The counter EMF of a shunt motor is 218V, the field resistance is 150Ω and the field current is 1.5A. The line current is 36.5A.

a. Find the armature resistance

b. If the line current during the start-up must be limited to 55A, How much starter resistance must be added in series with the armature?

c. What is the horse power developed by the motor? If the mechanical & iron losses total 550W, What is the horse power output?

DC SHUNT MOTOR SELF EXCITED

4. The efficiency at rated load of 100-hp 600-V shunt motor is 85%. The field resistance is 190Ω and the armature resistance is 0.22Ω. The full-load speed is 1200rpm.

Find (a) The rated line current

(b) The field current

(c) The armature current at full load

(d) The counter emf at full load

DC SHUNT MOTOR SELF EXCITED