Speed Control – Verified PYQ Authority Guide
Speed Control is a sub-topic revision hub built around verified PYQ evidence. It connects the recurring question patterns inside this sub-topic with the formulas, exam tips, common traps and concept pages already present in SRO. Every factual learning cue below is drawn from the existing verified, published and approved English PYQ corpus or from its Knowledge Graph relationships; the hub does not invent unsupported technical claims.
PYQ evidence snapshot
3 verified PYQs are currently mapped to this Sub Topic hub. The represented years include 2024, 2026. Exam coverage currently includes BMS, Additional Assistant Engineer (Electrical). Subject context includes Electrical Engineering. These values come from live mappings and can expand automatically when new verified PYQs are added.
Most useful verified PYQs to solve first
Start with the actual questions rather than memorising a generic note. The links below are ranked from the mapped corpus using repeat history and editorial quality, while the complete explanation stays on the individual question page.
- The speed control of a dc shunt motor in both directions can be obtained by
BMS · 2024 · Bidirectional Speed Control of DC Shunt Motor
Speed magnitude can be varied by armature-voltage/field control, while direction reversal requires reversing either armature current or field flux (but not both). The control… - The speed of a separately excited DC motor can be controlled by changing 1. Field current 2. Supply voltage 3. Armature resistance Select the correct option:
BMS · 2024 · Separately Excited DC Motor Speed Control
For a separately excited DC motor, speed is approximately N∝(V−IaRa)/Φ. Therefore speed can be controlled by changing armature supply voltage V, field current (which… - In flux control (field weakening), how does reducing the field current affect the motor's speed and torque?
Additional Assistant Engineer (Electrical) · 2026 · Field Weakening
DC motor speed is approximately inversely proportional to flux, so weakening the field raises speed. Since electromagnetic torque T ∝ ΦI_a, reducing flux reduces…
Formula & key-relationship bank from verified solutions
T∝ΦIa; reverse either Φ or Ia → reverse torque/directionN∝(V−IaRa)/ΦN ∝ (V-I_aR_a)/Φ ; T ∝ ΦI_a
Use these as revision triggers and open the linked PYQ before applying a formula numerically; variable definitions and assumptions belong to the exact solved question.
Core ideas repeatedly reinforced by the solved corpus
- Speed magnitude can be varied by armature-voltage/field control, while direction reversal requires reversing either armature current or field flux (but not both). The control arrangement in option B provides speed control in both rotational directions.
- For a separately excited DC motor, speed is approximately N∝(V−IaRa)/Φ. Therefore speed can be controlled by changing armature supply voltage V, field current (which changes flux Φ), or effective armature-circuit resistance. All three listed methods are valid, so…
- DC motor speed is approximately inversely proportional to flux, so weakening the field raises speed. Since electromagnetic torque T ∝ ΦI_a, reducing flux reduces torque available for a given armature current.
Exam tips already validated in SRO solutions
- To reverse a DC motor, reverse one of armature or field polarity—not both.
- DC motor speed has three main levers: armature voltage, field flux and armature resistance.
- Field weakening = above-base speed, reduced torque capability.
Common mistakes to avoid
- Reversing both armature and field leaves torque direction unchanged.
- Do not assume field control is the only speed-control method for a separately excited motor.
Topic and concept coverage
Mapped topic labels include DC Motors. The concept trail includes Bidirectional Speed Control of DC Shunt Motor, Field Weakening, Separately Excited DC Motor Speed Control. Use these labels as a revision map: move from the broad area to the narrow concept, solve a verified PYQ, inspect the detailed reasoning, and then attempt another question from the same cluster.
Knowledge Graph navigation
Continue with DC Motors, Bidirectional Speed Control of DC Shunt Motor, Field Weakening, Separately Excited DC Motor Speed Control, Electrical Machines, Electrical Engineering. These are canonical SRO entity links based on the Knowledge Graph and shared question mappings, not keyword-stuffed tag pages.
How to revise this authority page efficiently
- Solve before reading: answer a mapped PYQ first.
- Read the exact explanation: verify the correct principle, formula, distractor logic and common mistake on that question page.
- Move one level in the graph: use the closest concept/sub-topic/topic link rather than opening unrelated content.
- Reattempt: solve another verified PYQ from this hub and check whether the same error repeats.
Quality scope: this page is automatically maintained from SRO’s verified mapped corpus. It enriches one canonical authority URL instead of generating multiple near-duplicate pages for keyword variants. Manual authority articles are never overwritten by the automated engine.