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3-Phase Servo AVR (AC Voltage Stabilizer) — Parts, Tests, Repair & Maintenance

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3-Phase Servo AVR (AC Voltage Stabilizer) — Troubleshooting, Repair & Maintenance By Edwin Ogie • December 18, 2025 • -- AC Voltage Stabilizer — 3-phase servo control type (example from user photo) A practical, step-by-step guide to diagnose, repair and maintain 3-phase servo Automatic Voltage Regulators (AVR) / servo voltage stabilizers. Written in simple terms for technicians and maintenance teams working with generators, UPS rooms and factories. Includes videos, spare-parts list, safety checklist, troubleshooting flow and links to internal/external resources. Contents Why this matters In environments with unstable mains (frequent sags, surges or phase imbalance) a servo AVR protects sensitive equipment by continuously adjusting an autotransformer tap via a small servo motor. A well-maintained stabilizer saves equipment, reduces downtime and prevents costly damage. ...
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Variation (Direct, Inverse, Joint, Partial & Percentage Changes)

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EO

Variation — Edwin Ogie Library

Direct, inverse, joint, partial variations & percentage changes — worked examples and CBT for students.

Keywords: variation, proportionality Edwin Ogie Library

Introduction to Variation

Variation describes how one quantity changes with another. We study direct, inverse, joint, partial variations and percentage increases/decreases to solve many real-world and exam problems.

Quick links: Edwin Ogie Library (home) • Jump to CBT Quiz

Direct Variation

If y varies directly as x then y ∝ x or y = kx, where k is constant of proportionality.

Example

Q: y = 20 when x = 4. Find y when x = 10.

Inverse Variation

If y varies inversely as x: y ∝ 1/x or y = k / x.

Example

Q: y = 3 when x = 8. Find y when x = 16.

Joint & Partial Variation

Joint:

If y varies jointly as x and z: y = k x z.

Partial:

Partial/combined: y = k x + c (kx varies, c is constant).

Example (Joint)

Q: z = 30 when x=2 and y=5; find z when x=3 and y=4 (assuming z = kxy).

Percentage Increase & Decrease

Increase = [(New − Old)/Old] × 100%

Decrease = [(Old − New)/Old] × 100%

Example

Q: 80 → 100: percentage increase?

10 Worked Examples (Solutions Hidden)

Example 1 — Direct Variation

Q: If y varies directly as x and y=20 when x=4, find y when x=10.

Example 2 — Inverse Variation

Q: y=3 when x=8; find y when x=16.

Example 3 — Joint Variation

Q: z=30 when x=2, y=5; find z when x=3, y=4.

Example 4 — Partial Variation

Q: If y = 2x + 5, find y when x = 7.

Example 5 — Percentage Increase

Q: 80 → 100: % increase?

Example 6 — Percentage Decrease

Q: 120 → 90: % decrease?

Example 7 — Direct Variation % Change

Q: If x increases 20% in y = kx, what % does y increase?

Example 8 — Inverse Variation % Change

Q: y = k/x; x increases 50% → % change in y?

Example 9 — Joint Variation with change

Q: z=48 when x=4,y=3. If x+25% and y−20%, what's z?

Example 10 — Partial Variation & %

Q: y = 3x + 10; x increases 10% — approximate % change in y?

Summary

  • Direct: y = kx
  • Inverse: y = k / x
  • Joint: y = k x z (or more variables)
  • Partial: y = kx + c
  • Percentage change: Use original value as base.

30-Question CBT Quiz (15 minutes)

Designed for JSS to early senior students. Click Start Quiz to begin.

Time Remaining: 15:00
Resources: Edwin Ogie Library.
Edwin Ogie Library — learn, practice, and prepare.

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