Skip to main content
ElectraCore
LearnCalculatorsCircuit DesignerReferences
Saved
Educational use: ElectraCore supports learning and preliminary checks. It does not replace a competent electrician or engineer. Verify results, equipment data, and current local regulations before installation or live work.
Courses/Industrial Control & PLCs/Control Circuit Diagrams

lesson · 13min · Lesson 13 of 30

Drawing a full DOL control circuit

Course syllabusCourse overview
01Motor Starters
  1. ReadDOL starter: main and control circuit
  2. ReadStar-delta starter: wiring and timer
  3. ReadSoft starters: operation and parameters
  4. ReadVariable speed drives: inverter drives
  5. quizMotor starter quiz
02Contactors & Overloads
  1. ReadContactor construction and ratings
  2. ReadAuxiliary contacts and interlocking
  3. ReadThermal overload relays: setting the dial
  4. ReadElectronic overloads and motor protection relays
  5. exerciseContactor circuit problems
03Control Circuit Diagrams
  1. ReadIEC 60617 symbols: reading control diagrams
  2. ReadLadder diagrams: European and American styles
  3. ReadDrawing a full DOL control circuit
  4. ReadForward-reverse motor control
  5. exerciseDiagram reading exercises
04Safety Systems
  1. ReadEmergency stop requirements: IEC 60204
  2. ReadSafety relays and safety PLCs
  3. ReadLight curtains and safety interlocks
  4. ReadSafe isolation: EAWR and multi-energy control
  5. quizSafety systems quiz
05PLC Fundamentals
  1. ReadWhat is a PLC and where is it used?
  2. ReadPLC architecture: CPU, I/O modules, power
  3. ReadLadder logic basics: contacts and coils
  4. ReadTimers and counters in ladder logic
  5. exerciseWriting a simple motor control program
06Panel Layout & Installation
  1. ReadPanel design: layout and component spacing
  2. ReadCable management inside panels
  3. ReadLabelling, ferrules, and documentation
  4. ReadPanel testing and commissioning checklist
  5. quizFinal assessment
Lesson · 13min
DOL STARTER · CONTROL CIRCUITLNSTOPOL NCSTART NOKM1KM1 aux NO (seal-in)3~control rung shown; power poles and motor protection are separate
Lesson contents 0%

In this lesson

PurposeCore theoryWorked exampleKnowledge checkSources

In this lesson

PurposeCore theoryWorked exampleKnowledge checkSources
0% read
ElectraCore lesson handout

Drawing a full DOL control circuit

Industrial Control · Lesson 13 · Advanced

AdvancedReview: professional review pending

Purpose

Develop a complete DOL control circuit from requirements, including permissives, overload action, restart behavior and documentation.

Before you beginMotor starter circuits · Machine hazard and protection fundamentals

Learning objectives

  • Read state and cross-references
  • Separate standard control from safety functions
  • Analyse faults and reset behavior
  • Validate the complete input-logic-output path

Drawing a DOL rung begins with a cause-and-effect specification: what starts, what stops, what must be healthy, what happens after power loss, and which functions are safety-related.

CONTROL DIAGRAM STATE AND INTERLOCKSCONTROL DIAGRAM STATE AND INTERLOCKSSUPPLYSTARTERmotor · loadshort circuit · overload · command · interlock · isolation

Core theory

Define control supply/protection, stop chain, start command, seal-in contact, overload trip, permissives, coil and indication with terminal/wire references.

Select undervoltage/restart behavior deliberately. A three-wire momentary start scheme commonly prevents automatic restart after supply restoration; two-wire maintained commands behave differently.

Document the main power path and protective coordination separately. Validate all modes, including local/remote selection, overload reset and welded/stuck contact indications.

Terms, symbols, and units
TermMeaningSymbolUnit
PermissiveCondition required before or during operationNot applicableNot applicable
Three-wire controlMomentary start/stop scheme normally using a holding contactNot applicableNot applicable
Undervoltage releaseLoss of maintained operation when control voltage fallsNot applicableNot applicable
Worked exampleA maintained remote RUN contact remains closed through a power failure.

Assumptions: Symbols and terminal designations are defined by the supplied drawing set; Required safety performance comes from the machine risk assessment.

  1. Power loss: The coil drops out.
  2. Power return: The maintained command may immediately re-energize the coil.
  3. Decision: Use the risk assessment to require reset/start logic or another restart prevention measure.

Automatic restart is credible and must be deliberately prevented or justified and validated.

Reasonableness check: The conclusion is checked across normal, demand, fault, reset and restart states rather than inferred from one component label.

Common mistakes
  • Reading a contact in the energized instead of defined normal state
  • Using an ordinary PLC bit as an unvalidated safety function
  • Assuming emergency stop isolates every energy source

Where this appears in practice

Clear diagrams and validated safety functions let competent people build, test, diagnose and modify machinery without losing the intended protective behavior.

SafetyDo not bypass guards, light curtains, interlocks or safety outputs for production or diagnosis. Control hazardous electrical, pneumatic, hydraulic, gravitational and stored energy; isolate, lock off and prove dead using the site procedure before access.
Local code checkUse the current machine risk assessment, applicable type-C standard, IEC/BS EN 60204-1, ISO/BS EN ISO 13849-1 or IEC/BS EN 62061 design route, IEC 61496 where applicable, Electricity at Work Regulations, site lockout procedure and manufacturer validation instructions. BS 7671 Section 514 identification/notices does not by itself define or authorize the complete safe-isolation procedure.

Knowledge check

Does every DOL control circuit inherently prevent restart after power restoration?

No. Behavior depends on command architecture and state retention.

Answer: No. Behavior depends on command architecture and state retention.

Practical exercise

Write requirements, a rung, wire schedule and state test for local/remote DOL control with restart prevention.

Summary

  • A diagram is a state model plus physical cross-reference
  • Safety performance belongs to the complete function
  • Stop, emergency stop and isolation are distinct

Sources and review

  • IEC 60204-1:2016+AMD1:2021: Electrical equipment of machines: IEC; 6.1; International
  • ISO 13849-1:2023: Safety-related parts of control systems: ISO; 2023; International
  • IEC 62061:2021 with current amendments: Functional safety of machinery control systems: IEC; 2021; confirm current consolidated version; International
  • IEC 61496-1:2020: Electro-sensitive protective equipment: IEC; 2020; International
  • Electricity at Work Regulations 1989: UK Legislation; Current official text; Great Britain

Editorial review date: 2026-08-22. Professional electrical review is pending.

Educational material for learning and preliminary checks. Verify current local requirements and exact equipment instructions. This lesson does not replace competent professional work.

Personal study record

Lesson notes

Ready

Notes are stored on this device unless you export them.