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Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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______________ has a relatively wider range of speed control.
Synchronous motor
shunt motor
Ship ring induction motor
Squirrel cage induction motor
shunt motor
Quick Summary: A D.C. shunt motor allows for a wide and smooth range of speed control by adjusting the field flux or armature voltage. This makes it superior to induction or synchronous motors, which generally operate at fixed speeds governed by supply frequency and pole pairs.
A D.C. shunt motor allows for a wide and smooth range of speed control by adjusting the field flux or armature voltage. This makes it superior to induction or synchronous motors, which generally operate at fixed speeds governed by supply frequency and pole pairs.
N=KΦV−IaRa — Fundamental speed equation for a DC motor
Pmech=EbIa — Mechanical power developed
The speed of a DC motor is governed by the relation N∝ΦEb. By controlling the shunt field current using a rheostat, the flux Φ can be varied, resulting in speed variations above the rated value (field control). Alternatively, varying the applied armature voltage V allows for speeds below the rated value (armature control), providing a versatile operational envelope.
Speed control in DC shunt motors is achieved without the need for complex power electronics (though they are now commonly used).
Field control provides constant power drive characteristics.
Armature control provides constant torque drive characteristics.
Synchronous motors run at a constant speed defined by Ns=P120f.
Wide range of speed control
Smooth and precise speed regulation
Simple control circuit
Requires DC supply or rectifier
Maintenance due to brushes and commutator
Lower efficiency compared to brushless AC motors
Machine tools
Lathes
Conveyor belts
Fans and blowers
| Feature | DC Shunt Motor | Synchronous Motor |
|---|---|---|
Speed Control | Wide and smooth (Flux/Voltage control) | Fixed speed (Synchronous) |
The Squirrel cage induction motor is primarily a constant speed motor; speed variation requires Variable Frequency Drives (VFDs).
Slip ring induction motors allow speed control via rotor resistance, but it is less efficient due to heat loss in resistors.
B is correct — The D.C. shunt motor provides a relatively wider range of speed control through armature voltage and field flux variation.
Always remember that in DC motors, field weakening (Φ↓) increases speed, whereas in AC induction motors, changing frequency (f) is the primary method for speed control.