Learning to implement Structured Text for Motor Control using Delta's WPLSoft / ISPSoft / DIADesigner-AX is an essential skill for PLC programmers working in Industrial Manufacturing. This comprehensive guide walks you through the fundamentals, providing clear explanations and practical examples that you can apply immediately to real-world projects.
Delta has established itself as Strong in Asian, Indian, and SE Asian OEM machinery — packaging, plastics, textiles, HVAC, food processing — and in cost-sensitive water-treatment, irrigation, and small-plant work across Latin America and EMEA, making it a strategic choice for Motor Control applications. With ~3–4% global, growing global market share and 7 popular PLC families including the DVP-ES2 / EX2 / SS2 (compact entry) and DVP-SX2 / SA2 / SV2 (motion + analogue), Delta provides the robust platform needed for beginner to intermediate complexity projects like Motor Control.
The Structured Text approach is particularly well-suited for Motor Control because complex calculations, data manipulation, advanced control algorithms, and when code reusability is important. This combination allows you to leverage powerful for complex logic while managing the typical challenges of Motor Control, including soft start implementation and overload protection.
Throughout this guide, you'll discover step-by-step implementation strategies, working code examples tested on WPLSoft / ISPSoft / DIADesigner-AX, and industry best practices specific to Industrial Manufacturing. Whether you're programming your first Motor Control system or transitioning from another PLC platform, this guide provides the practical knowledge you need to succeed with Delta Structured Text programming.
Delta WPLSoft / ISPSoft / DIADesigner-AX for Motor Control
Delta's PLC programming ecosystem is split between two free Windows IDEs: WPLSoft for the legacy DVP-ES2 / EX2 / SS2 / SX2 / SA2 / SV2 / EH3 family, and ISPSoft for newer DVP-SE / SV2 / SX3 models and the AH and AS mid-range series. WPLSoft is a focused ladder-and-IL editor with an offline simulator, online monitoring with rung-state colour, and built-in Modbus RTU / TCP wizards. ISPSoft is IEC 61131-3 oriented — ladder, structured text, function block diagram and SFC — with project-tree organis...
Platform Strengths for Motor Control:
- Free WPLSoft and ISPSoft IDEs with built-in offline simulator
- Full IEC 61131-3 language coverage on AH / AS / AX series via ISPSoft
- Mitsubishi-FX-style instruction set easing migration on DVP
- Aggressive pricing typically 30–50% below Siemens or Allen-Bradley
Unique ${brand.software} Features:
- Free WPLSoft IDE for DVP series with built-in offline simulator
- Free ISPSoft IDE for AH / AS / DVP-SE with full IEC 61131-3 language coverage
- Mitsubishi-FX-style instruction set easing migration for FX-trained engineers
- Built-in Modbus RTU and Modbus TCP master / slave on most CPUs
Key Capabilities:
The WPLSoft / ISPSoft / DIADesigner-AX environment excels at Motor Control applications through its free wplsoft and ispsoft ides with built-in offline simulator. This is particularly valuable when working with the 5 sensor types typically found in Motor Control systems, including Current sensors, Vibration sensors, Temperature sensors.
Control Equipment for Motor Control:
- Motor control centers (MCCs)
- AC induction motors (NEMA/IEC frame)
- Synchronous motors for high efficiency
- DC motors for precise speed control
Delta's controller families for Motor Control include:
- DVP-ES2 / EX2 / SS2 (compact entry): Suitable for beginner to intermediate Motor Control applications
- DVP-SX2 / SA2 / SV2 (motion + analogue): Suitable for beginner to intermediate Motor Control applications
- DVP-SE (Ethernet): Suitable for beginner to intermediate Motor Control applications
- DVP-EH3 (legacy high-end): Suitable for beginner to intermediate Motor Control applications
Hardware Selection Guidance:
DVP-ES2 / EX2 / SS2 cover compact entry-level for small machines; DVP-SX2 adds analogue I/O; DVP-SA2 / SV2 step up for motion-heavy applications; DVP-SE adds Ethernet; DVP-EH3 is the legacy high-end. For mid-range process and machine control, AS-series (AS218 / AS228 / AS318 / AS332) and AH-series (AH500 modular rack) are preferred. AX-series motion controllers handle EtherCAT-based multi-axis. Se...
Industry Recognition:
Strong in Asian, Indian, and SE Asian OEM machinery — packaging, plastics, textiles, HVAC, food processing — and in cost-sensitive water-treatment, irrigation, and small-plant work across Latin America and EMEA. Tier 2 / Tier 3 component fixturing and ancillary equipment in Asian and Indian automotive supply chains. Limited Tier 1 line-control presence — OEMs typically specify Siemens or Mitsubishi at that tier....
Investment Considerations:
With $ pricing, Delta positions itself in the value segment. For Motor Control projects requiring beginner skill levels and 1-3 weeks development time, the total investment includes hardware, software licensing, training, and ongoing support.
Understanding Structured Text for Motor Control
Structured Text (ST) is a high-level, text-based programming language defined in IEC 61131-3. It resembles Pascal and provides powerful constructs for complex algorithms, calculations, and data manipulation.
Execution Model:
Code executes sequentially from top to bottom within each program unit. Variables maintain state between scan cycles unless explicitly reset.
Core Advantages for Motor Control:
- Powerful for complex logic: Critical for Motor Control when handling beginner to intermediate control logic
- Excellent code reusability: Critical for Motor Control when handling beginner to intermediate control logic
- Compact code representation: Critical for Motor Control when handling beginner to intermediate control logic
- Good for algorithms and calculations: Critical for Motor Control when handling beginner to intermediate control logic
- Familiar to software developers: Critical for Motor Control when handling beginner to intermediate control logic
Why Structured Text Fits Motor Control:
Motor Control systems in Industrial Manufacturing typically involve:
- Sensors: Current transformers for motor current monitoring, RTD or thermocouple for motor winding temperature, Vibration sensors for bearing monitoring
- Actuators: Contactors for direct-on-line starting, Soft starters for reduced voltage starting, Variable frequency drives for speed control
- Complexity: Beginner to Intermediate with challenges including Managing starting current within supply limits
Programming Fundamentals in Structured Text:
Variables:
- declaration: VAR / VAR_INPUT / VAR_OUTPUT / VAR_IN_OUT / VAR_GLOBAL sections
- initialization: Variables can be initialized at declaration: Counter : INT := 0;
- constants: VAR CONSTANT section for read-only values
Operators:
- arithmetic: + - * / MOD (modulo)
- comparison: = <> < > <= >=
- logical: AND OR XOR NOT
ControlStructures:
- if: IF condition THEN statements; ELSIF condition THEN statements; ELSE statements; END_IF;
- case: CASE selector OF value1: statements; value2: statements; ELSE statements; END_CASE;
- for: FOR index := start TO end BY step DO statements; END_FOR;
Best Practices for Structured Text:
- Use meaningful variable names with consistent naming conventions
- Initialize all variables at declaration to prevent undefined behavior
- Use enumerated types for state machines instead of magic numbers
- Break complex expressions into intermediate variables for readability
- Use functions for reusable calculations and function blocks for stateful operations
Common Mistakes to Avoid:
- Using = instead of := for assignment (= is comparison)
- Forgetting semicolons at end of statements
- Integer division truncation - use REAL for decimal results
- Infinite loops from incorrect WHILE/REPEAT conditions
Typical Applications:
1. PID control: Directly applicable to Motor Control
2. Recipe management: Related control patterns
3. Statistical calculations: Related control patterns
4. Data logging: Related control patterns
Understanding these fundamentals prepares you to implement effective Structured Text solutions for Motor Control using Delta WPLSoft / ISPSoft / DIADesigner-AX.
Implementing Motor Control with Structured Text
Motor control systems use PLCs to start, stop, and regulate electric motors in industrial applications. These systems provide protection, speed control, and coordination for motors ranging from fractional horsepower to thousands of horsepower.
This walkthrough demonstrates practical implementation using Delta WPLSoft / ISPSoft / DIADesigner-AX and Structured Text programming.
System Requirements:
A typical Motor Control implementation includes:
Input Devices (Sensors):
1. Current transformers for motor current monitoring: Critical for monitoring system state
2. RTD or thermocouple for motor winding temperature: Critical for monitoring system state
3. Vibration sensors for bearing monitoring: Critical for monitoring system state
4. Speed encoders or tachometers: Critical for monitoring system state
5. Torque sensors for load monitoring: Critical for monitoring system state
Output Devices (Actuators):
1. Contactors for direct-on-line starting: Primary control output
2. Soft starters for reduced voltage starting: Supporting control function
3. Variable frequency drives for speed control: Supporting control function
4. Brakes (mechanical or dynamic): Supporting control function
5. Starters (star-delta, autotransformer): Supporting control function
Control Equipment:
- Motor control centers (MCCs)
- AC induction motors (NEMA/IEC frame)
- Synchronous motors for high efficiency
- DC motors for precise speed control
Control Strategies for Motor Control:
1. Primary Control: Industrial motor control using PLCs for start/stop, speed control, and protection of electric motors.
2. Safety Interlocks: Preventing Soft start implementation
3. Error Recovery: Handling Overload protection
Implementation Steps:
Step 1: Calculate motor starting current and verify supply capacity
In WPLSoft / ISPSoft / DIADesigner-AX, calculate motor starting current and verify supply capacity.
Step 2: Select starting method based on motor size and load requirements
In WPLSoft / ISPSoft / DIADesigner-AX, select starting method based on motor size and load requirements.
Step 3: Configure motor protection with correct thermal curve
In WPLSoft / ISPSoft / DIADesigner-AX, configure motor protection with correct thermal curve.
Step 4: Implement control logic for start/stop with proper interlocks
In WPLSoft / ISPSoft / DIADesigner-AX, implement control logic for start/stop with proper interlocks.
Step 5: Add speed control loop if VFD is used
In WPLSoft / ISPSoft / DIADesigner-AX, add speed control loop if vfd is used.
Step 6: Configure acceleration and deceleration ramps
In WPLSoft / ISPSoft / DIADesigner-AX, configure acceleration and deceleration ramps.
Delta Function Design:
WPLSoft P-labels are the primary reuse mechanism on DVP. ISPSoft instance-based function blocks enable proper IEC-style reuse on AH / AS, with library import / export. Delta-supplied motion, communication, and PID FBs ship with the IDE.
Common Challenges and Solutions:
1. Managing starting current within supply limits
- Solution: Structured Text addresses this through Powerful for complex logic.
2. Coordinating acceleration with driven load requirements
- Solution: Structured Text addresses this through Excellent code reusability.
3. Protecting motors from frequent starting (thermal cycling)
- Solution: Structured Text addresses this through Compact code representation.
4. Handling regenerative energy during deceleration
- Solution: Structured Text addresses this through Good for algorithms and calculations.
Safety Considerations:
- Proper machine guarding for rotating equipment
- Emergency stop functionality with safe torque off
- Lockout/tagout provisions for maintenance
- Arc flash protection and PPE requirements
- Proper grounding and bonding
Performance Metrics:
- Scan Time: Optimize for 5 inputs and 5 outputs
- Memory Usage: Efficient data structures for DVP-ES2 / EX2 / SS2 (compact entry) capabilities
- Response Time: Meeting Industrial Manufacturing requirements for Motor Control
Delta Diagnostic Tools:
WPLSoft / ISPSoft online monitor with rung-state colour,Soft-element watch table and tag watch lists,Built-in offline simulator (WPLSoft and ISPSoft),Modbus RTU / TCP communication wizard with diagnostic counters,DIADesigner-AX integrated diagnostics for AX motion projects,M1000-range system flags for CPU and comms diagnostics,Delta distributor support and loaner CPUs in major markets,Delta IA forum and DeltaPLC community for application questions
Delta's WPLSoft / ISPSoft / DIADesigner-AX provides tools for performance monitoring and optimization, essential for achieving the 1-3 weeks development timeline while maintaining code quality.
Delta Structured Text Example for Motor Control
Complete working example demonstrating Structured Text implementation for Motor Control using Delta WPLSoft / ISPSoft / DIADesigner-AX. Follows Delta naming conventions. Tested on DVP-ES2 / EX2 / SS2 (compact entry) hardware.
(* Delta WPLSoft / ISPSoft / DIADesigner-AX - Motor Control Control *)
(* Structured Text Implementation for Industrial Manufacturing *)
(* WPLSoft / DVP work is dominated by raw soft-element addressing (X0, Y0 *)
PROGRAM PRG_MOTOR_CONTROL_Control
VAR
(* State Machine Variables *)
eState : E_MOTOR_CONTROL_States := IDLE;
bEnable : BOOL := FALSE;
bFaultActive : BOOL := FALSE;
(* Timers *)
tonDebounce : TON;
tonProcessTimeout : TON;
tonFeedbackCheck : TON;
(* Counters *)
ctuCycleCounter : CTU;
(* Process Variables *)
rCurrentsensors : REAL := 0.0;
rMotorstarters : REAL := 0.0;
rSetpoint : REAL := 100.0;
END_VAR
VAR CONSTANT
(* Industrial Manufacturing Process Parameters *)
C_DEBOUNCE_TIME : TIME := T#500MS;
C_PROCESS_TIMEOUT : TIME := T#30S;
C_BATCH_SIZE : INT := 50;
END_VAR
(* Input Conditioning *)
tonDebounce(IN := bStartButton, PT := C_DEBOUNCE_TIME);
bEnable := tonDebounce.Q AND NOT bEmergencyStop AND bSafetyOK;
(* Main State Machine - Pattern: FX-style SFC steps (S0..S1023) for clean *)
CASE eState OF
IDLE:
rMotorstarters := 0.0;
ctuCycleCounter(RESET := TRUE);
IF bEnable AND rCurrentsensors > 0.0 THEN
eState := STARTING;
END_IF;
STARTING:
(* Ramp up output - Gradual start *)
rMotorstarters := MIN(rMotorstarters + 5.0, rSetpoint);
IF rMotorstarters >= rSetpoint THEN
eState := RUNNING;
END_IF;
RUNNING:
(* Motor Control active - Motor control systems use PLCs to start, stop, and *)
tonProcessTimeout(IN := TRUE, PT := C_PROCESS_TIMEOUT);
ctuCycleCounter(CU := bCyclePulse, PV := C_BATCH_SIZE);
IF ctuCycleCounter.Q THEN
eState := COMPLETE;
ELSIF tonProcessTimeout.Q THEN
bFaultActive := TRUE;
eState := FAULT;
END_IF;
COMPLETE:
rMotorstarters := 0.0;
(* Log production data - PLC-tier logging is uncommon on DVP — logging happens at the HMI tier (DOPSoft, Delta DIAView SCADA) or via Modbus pull from a higher-level historian. AH / AS supports SD-card data logging and on-board CSV export. *)
eState := IDLE;
FAULT:
rMotorstarters := 0.0;
(* M-flag banks latched on fault detection on DVP; ISPSoft on AH / AS allows alarm structures and HMI alarm-banner integration via Delta DOPSoft or third-party HMIs over Modbus TCP. *)
IF bFaultReset AND NOT bEmergencyStop THEN
bFaultActive := FALSE;
eState := IDLE;
END_IF;
END_CASE;
(* Safety Override - Always executes *)
IF bEmergencyStop OR NOT bSafetyOK THEN
rMotorstarters := 0.0;
eState := FAULT;
bFaultActive := TRUE;
END_IF;
END_PROGRAMCode Explanation:
- 1.Enumerated state machine (FX-style SFC steps (S0..S1023) for clean sequencer logic on DVP; integer state in D-registers for fault-recovery branching. ISPSoft on AH / AS supports IEC-style state-machine function blocks with structured-text guards.) for clear Motor Control sequence control
- 2.Constants define Industrial Manufacturing-specific parameters: cycle time 30s, batch size
- 3.Input conditioning with debounce timer prevents false triggers in industrial environment
- 4.STARTING state implements soft-start ramp - prevents mechanical shock
- 5.Process timeout detection identifies stuck conditions - critical for reliability
- 6.Safety override section executes regardless of state - Delta best practice for beginner to intermediate systems
Best Practices
- ✓Follow Delta naming conventions: WPLSoft / DVP work is dominated by raw soft-element addressing (X0, Y0, M100, D1
- ✓Delta function design: WPLSoft P-labels are the primary reuse mechanism on DVP. ISPSoft instance-based
- ✓Data organization: DVP has no structured data blocks — D / register banks are documented by range.
- ✓Structured Text: Use meaningful variable names with consistent naming conventions
- ✓Structured Text: Initialize all variables at declaration to prevent undefined behavior
- ✓Structured Text: Use enumerated types for state machines instead of magic numbers
- ✓Motor Control: Verify motor running with current or speed feedback, not just contactor status
- ✓Motor Control: Implement minimum off time between starts for motor cooling
- ✓Motor Control: Add phase loss and phase reversal protection
- ✓Debug with WPLSoft / ISPSoft / DIADesigner-AX: Run the offline simulator with forced inputs before live download
- ✓Safety: Proper machine guarding for rotating equipment
- ✓Use WPLSoft / ISPSoft / DIADesigner-AX simulation tools to test Motor Control logic before deployment
Common Pitfalls to Avoid
- ⚠Structured Text: Using = instead of := for assignment (= is comparison)
- ⚠Structured Text: Forgetting semicolons at end of statements
- ⚠Structured Text: Integer division truncation - use REAL for decimal results
- ⚠Delta common error: Battery-low alarm on legacy DVP-EH causing D-range data loss
- ⚠Motor Control: Managing starting current within supply limits
- ⚠Motor Control: Coordinating acceleration with driven load requirements
- ⚠Neglecting to validate Current transformers for motor current monitoring leads to control errors
- ⚠Insufficient comments make Structured Text programs unmaintainable over time
Related Certifications
Mastering Structured Text for Motor Control applications using Delta WPLSoft / ISPSoft / DIADesigner-AX requires understanding both the platform's capabilities and the specific demands of Industrial Manufacturing. This guide has provided comprehensive coverage of implementation strategies, working code examples, best practices, and common pitfalls to help you succeed with beginner to intermediate Motor Control projects.
Delta's ~3–4% global, growing market share and strong in asian, indian, and se asian oem machinery — packaging, plastics, textiles, hvac, food processing — and in cost-sensitive water-treatment, irrigation, and small-plant work across latin america and emea demonstrate the platform's capability for demanding applications. The platform excels in Industrial Manufacturing applications where Motor Control reliability is critical.
By following the practices outlined in this guide—from proper program structure and Structured Text best practices to Delta-specific optimizations—you can deliver reliable Motor Control systems that meet Industrial Manufacturing requirements.
Next Steps for Professional Development:
1. Certification: Pursue Delta IA Academy distributor-led engineer training to validate your Delta expertise
2. Advanced Training: Consider WPLSoft / ISPSoft course completions for specialized Industrial Manufacturing applications
3. Hands-on Practice: Build Motor Control projects using DVP-ES2 / EX2 / SS2 (compact entry) hardware
4. Stay Current: Follow WPLSoft / ISPSoft / DIADesigner-AX updates and new Structured Text features
Structured Text Foundation:
Structured Text (ST) is a high-level, text-based programming language defined in IEC 61131-3. It resembles Pascal and provides powerful constructs for...
The 1-3 weeks typical timeline for Motor Control projects will decrease as you gain experience with these patterns and techniques. Remember: Verify motor running with current or speed feedback, not just contactor status
For further learning, explore related topics including Recipe management, Fan systems, and Delta platform-specific features for Motor Control optimization.