Every Industrial Engineer term, in study order

240 terms across 16 phases, in the order the deck teaches them. Each one gets a page you can read in a minute and a quiz that checks whether you did.

An open control cabinet with a PLC rack on DIN rail, processor and plug in modules seated in a row beside neatly combed wire duct.

PLC Controller Hardware

Phase 1 · 12 terms

The box itself, from processor and rack to the modules that plug into it, because nothing else in the deck lands until you know what a PLC physically is.

  1. 1 PLC Programmable Logic Controller, an industrial computer that executes deterministic control logic for machines and process...
  2. 2 CPU / Processor Controller module that executes the user program, manages memory and communications, and coordinates I/O updates.
  3. 3 Rack / Chassis Mechanical assembly that holds controller modules and connects them through a backplane.
  4. 4 Backplane Internal bus that distributes power and data between modules in a PLC rack or chassis.
  5. 5 Power Supply Module that converts incoming plant power to the regulated voltages required by the controller and its modules.
  6. 6 I/O Module Module that interfaces the PLC with discrete or analog field signals.
  7. 7 Local I/O I/O installed in the same rack or local assembly as the controller.
  8. 8 Remote I/O / Expansion I/O installed away from the controller and connected through an industrial network or expansion bus.
  9. 9 Communication Module Module that adds a network or serial communication interface to the controller.
  10. 10 Terminal Block Removable or fixed connector where field wiring lands on an I/O module or base.
  11. 11 Memory Card Removable storage used for program backup, firmware, recipes, or controller recovery.
  12. 12 Watchdog Timer Diagnostic timer that faults or resets the controller when program execution exceeds an allowed time or stops responding...
A close view of a terminal strip, ferruled field wires landed in tidy rows while a hand steadies a screwdriver against one terminal.

PLC I/O and Field Signals

Phase 2 · 20 terms

Where the controller meets the machine: discrete and analog signals, the wiring conventions behind them, and the field devices that send them.

  1. 13 DI / Discrete Input On or off input from a field device such as a switch, sensor, or pushbutton.
  2. 14 DO / Discrete Output On or off output used to command a relay, solenoid, starter, lamp, or other load.
  3. 15 AI / Analog Input Input that measures a continuous electrical signal such as 4-20 mA, 0-10 V, resistance, or thermocouple voltage.
  4. 16 AO / Analog Output Output that sends a continuous command signal such as 4-20 mA or 0-10 V to another device.
  5. 17 Sinking / Sourcing DC circuit convention describing whether a device provides the current return path or supplies current to the load.
  6. 18 PNP Sensor Three-wire DC sensor whose output sources positive current when active.
  7. 19 NPN Sensor Three-wire DC sensor whose output sinks current to DC common when active.
  8. 20 Dry Contact Voltage-free mechanical or solid-state contact that requires an external wetting voltage.
  9. 21 Wet Contact Contact or output that supplies a voltage when active.
  10. 22 Two-Wire Transmitter Analog transmitter powered through the same current loop that carries its measurement signal.
  11. 23 Three-Wire Sensor Powered sensor with separate positive supply, common, and signal conductors.
  12. 24 4-20 mA Current Loop Analog signaling method in which 4 mA represents the live zero and 20 mA represents full scale.
  13. 25 0-10 V Signal Voltage-based analog signal whose value is proportional to a configured engineering range.
  14. 26 Raw Counts Unscaled numeric value produced by an analog converter before conversion to engineering units.
  15. 27 Scaling Conversion between raw I/O counts and engineering units such as pressure, temperature, or speed.
  16. 28 Resolution Smallest input or output change an analog module can represent, commonly specified in bits or counts.
  17. 29 Isolation Electrical separation that limits unwanted current paths between field circuits, channels, and controller electronics.
  18. 30 Input Filter / Debounce Time or digital filtering used to reject contact bounce and short signal disturbances.
  19. 31 Fail-Safe State Predetermined output or process condition entered after a detected fault, communication loss, or power loss.
  20. 32 Normally Open / Normally Closed Contact state defined with the field device in its normal, unactuated, and de-energized condition.
A laptop propped on a steel toolbox in front of an open panel, its glow lighting the cabinet while a coiled cable runs from it into the rack.

PLC Program Organization and Execution

Phase 3 · 27 terms

How the logic is arranged and how the scan actually runs it, which is the difference between code that works and code that works every time.

  1. 33 Ladder Diagram (LD) IEC 61131-3 graphical language that represents logic with relay-style contacts, coils, and function blocks.
  2. 34 Function Block Diagram (FBD) IEC 61131-3 graphical language that connects functions and function blocks with signal lines.
  3. 35 Structured Text (ST) IEC 61131-3 textual language used for expressions, calculations, loops, and structured control logic.
  4. 36 Sequential Function Chart (SFC) IEC 61131-3 elements that organize programs and function blocks as steps, actions, and transitions.
  5. 37 Instruction List (IL, Legacy) Legacy mnemonic PLC language found in older systems but not included in the current IEC 61131-3:2025 language suite.
  6. 38 Program Top-level user-code organization unit that coordinates control logic and calls routines or function blocks.
  7. 39 Routine / Function Reusable or callable unit of logic that performs a defined operation.
  8. 40 Function Block Reusable program unit with defined inputs, outputs, and retained internal state when instantiated.
  9. 41 Task Execution container that schedules one or more programs by cyclic, periodic, or event-driven rules.
  10. 42 Continuous / Cyclic Task Task that runs repeatedly whenever higher-priority work and system overhead permit.
  11. 43 Periodic Task Task scheduled to run at a configured time interval.
  12. 44 Event Task Task triggered by a configured hardware, motion, network, or program event.
  13. 45 Scan Cycle Repeated controller operation that services inputs, executes scheduled logic, updates outputs, communicates, and perform...
  14. 46 Scan Time Elapsed time required for one controller execution cycle or one scheduled task pass.
  15. 47 First Scan Controller status that is true during the initial logic pass after entering run mode and is used for initialization.
  16. 48 Rung Horizontal network of conditions and instructions in ladder logic.
  17. 49 Coil / Contact Ladder elements that write a Boolean result or test a Boolean condition.
  18. 50 One-Shot / Edge Detection Instruction that becomes true for one execution when a Boolean signal changes state.
  19. 51 Latch / Unlatch Instructions that set or clear a stored Boolean state until an opposing instruction changes it.
  20. 52 Interlock Logic that prevents an operation when a condition would make it unsafe or damaging.
  21. 53 Permissive Condition that must be satisfied before an operation is allowed to start or continue.
  22. 54 Sequence / State Machine Logic that advances equipment through defined operating states based on commands, conditions, and transitions.
  23. 55 PID Control Closed-loop control calculation using proportional, integral, and derivative action to regulate a process variable.
  24. 56 Online Edit Program change made while the controller remains connected and, where supported, continues running.
  25. 57 Upload Transfer of the current project or data from the controller to the programming workstation.
  26. 58 Download Transfer of a project, logic, or configuration from the programming workstation to the controller.
  27. 59 Force Temporary override that commands an I/O point or tag to a selected state for testing and troubleshooting.
A hand seats a small memory card into a PLC processor module resting on a workbench mat, the connector pins sharp in the light.

PLC Memory, Tags, and Instructions

Phase 4 · 17 terms

The data a program moves and the instructions that move it, from a single true or false value up to a structured array.

  1. 60 Tag / Address Symbolic name or numeric location used to reference I/O, memory, or structured data.
  2. 61 Bit / BOOL Single Boolean value that is either false or true.
  3. 62 Byte / SINT Eight-bit data quantity, interpreted as bits or as a small integer according to its data type.
  4. 63 Word / INT / DINT Integer data types or registers commonly represented with 16 or 32 bits.
  5. 64 REAL / Float Floating-point data type used for fractional values and wide numeric ranges.
  6. 65 Array Indexed collection of elements that all share the same data type.
  7. 66 Structure / UDT Grouped data type that combines related members under one name.
  8. 67 Alias Tag Alternate tag name that references another tag or hardware-defined point.
  9. 68 Local / Global Tag Tag scoped to one program or made accessible across the controller project.
  10. 69 Retentive Memory Memory configured to preserve selected values through a power cycle or operating-mode change.
  11. 70 Nonretentive Memory Memory or instruction state that returns to its defined initial condition after specified resets or power cycles.
  12. 71 Timer (TON, TOF, TP) IEC timer functions for on-delay, off-delay, and pulse timing.
  13. 72 Retentive Timer Timer that preserves accumulated time until a reset instruction clears it.
  14. 73 Counter (CTU, CTD) Functions that count rising events upward or downward and expose completion status.
  15. 74 Compare Instruction Instruction that evaluates relationships such as equal, not equal, greater than, or less than.
  16. 75 Move / Copy Instructions that transfer a value or block of data without changing the source.
  17. 76 Mask Bit pattern used to select which bits participate in a comparison, copy, or logical operation.
An industrial switch on DIN rail with a fan of patch cables landing in it, link lights alive and the run dressed tight below.

PLC Industrial Communications

Phase 5 · 21 terms

The protocols that let controllers, drives and operator panels talk, plus the addressing and description files that make them agree on what was said.

  1. 77 EtherNet/IP ODVA industrial Ethernet network that uses the Common Industrial Protocol over standard Ethernet, TCP/IP, and UDP.
  2. 78 CIP Common Industrial Protocol, the object-oriented application protocol used by EtherNet/IP and other ODVA networks.
  3. 79 Implicit Messaging CIP communication used for time-critical cyclic I/O data through an established connection.
  4. 80 Explicit Messaging CIP request-and-response communication used for configuration, diagnostics, and noncyclic data.
  5. 81 RPI Requested Packet Interval, the configured rate at which a CIP I/O connection requests data updates.
  6. 82 EDS File Electronic Data Sheet that describes an industrial network device and its configurable attributes.
  7. 83 PROFINET Industrial Ethernet system maintained by PROFIBUS and PROFINET International for automation communication and real-time...
  8. 84 PROFIBUS Industrial fieldbus maintained by PROFIBUS and PROFINET International for controller and field-device communication.
  9. 85 GSD / GSDML File Device-description file used to configure a PROFIBUS or PROFINET device in an engineering system.
  10. 86 Modbus RTU Modbus protocol encoding commonly carried over RS-485 serial networks.
  11. 87 Modbus TCP Modbus application protocol transported over TCP/IP Ethernet.
  12. 88 Coils / Discrete Inputs One-bit read-write and read-only data areas in the Modbus data model.
  13. 89 Holding / Input Registers Sixteen-bit read-write and read-only data areas in the Modbus data model.
  14. 90 RS-232 / RS-485 Serial electrical interfaces used for point-to-point or multidrop industrial communication.
  15. 91 Baud Rate / Parity Serial communication settings that define bit timing and optional error checking and must match at both ends.
  16. 92 OPC UA Platform-independent industrial communication standard for structured, secure data exchange between systems.
  17. 93 IP Address / Subnet Mask Network settings that identify an Ethernet device and determine which addresses are locally reachable.
  18. 94 Default Gateway Router address used to reach devices outside the local IP subnet.
  19. 95 MAC Address Hardware-layer address assigned to an Ethernet network interface.
  20. 96 Managed Industrial Switch Ethernet switch with configuration and diagnostic features such as VLANs, port mirroring, redundancy, and traffic priori...
  21. 97 Device Level Ring (DLR) ODVA ring topology that provides rapid recovery from a single network break on supported EtherNet/IP devices.
A panel door up close: a red mushroom emergency stop, a keyed mode selector and a guarded switch, the paint worn thin where hands go.

PLC Operating Modes, Safety, and Diagnostics

Phase 6 · 15 terms

Run, program and fault: what a controller does when something goes wrong, and the safety functions that decide how much that costs.

  1. 98 Run Mode Controller state in which the enabled user program executes and outputs are controlled according to the project.
  2. 99 Program / Stop Mode Controller state used for editing or maintenance in which normal user logic and outputs are stopped or inhibited accordi...
  3. 100 Remote Mode Key-switch or controller state that permits operating-mode changes from programming software.
  4. 101 Major Fault Serious controller or program fault that can stop task execution or place the controller in a faulted state.
  5. 102 Minor Fault / Warning Diagnostic condition recorded by the controller that may allow logic execution to continue.
  6. 103 Alarm Reported abnormal condition that requires operator or maintenance attention but does not necessarily stop control.
  7. 104 Diagnostic Buffer / Fault Log Time-ordered record of controller, module, and network events used for troubleshooting.
  8. 105 Firmware Vendor-supplied embedded software that defines controller or module behavior and compatibility.
  9. 106 Safety PLC Controller designed and certified to execute safety-related logic within specified SIL or PL limits.
  10. 107 SIL Safety Integrity Level, a discrete integrity target for safety functions under IEC 61508 and related sector standards.
  11. 108 PL Performance Level, a safety-related control-system capability rating under ISO 13849-1.
  12. 109 Safety Task Protected and monitored controller task used to execute certified safety logic.
  13. 110 Dual-Channel Input Safety input arrangement using two monitored signal paths to improve fault detection.
  14. 111 Discrepancy Time Maximum allowed time difference between the expected state changes of paired safety channels.
  15. 112 Redundancy / Hot Standby Architecture using a synchronized backup controller or component that can assume control after a primary failure.
A plant floor seen down a line of machines, an operator panel on its pedestal in front and conveyors receding into the hall.

PLC Related Automation Systems

Phase 7 · 6 terms

The neighbours a PLC lives beside on a plant floor, from operator panels and SCADA up to the motion and batch systems it hands work to.

  1. 113 PAC Programmable Automation Controller, an industry term for a PLC-class controller with broad integration, motion, networki...
  2. 114 Soft PLC PLC runtime hosted on an industrial computer or virtualized platform instead of dedicated controller hardware.
  3. 115 HMI Human-Machine Interface used by operators to view status, enter commands, acknowledge alarms, and adjust setpoints.
  4. 116 SCADA Supervisory Control and Data Acquisition system that monitors and supervises distributed controllers and process equipme...
  5. 117 RTU Remote Terminal Unit designed to collect field data and control remote assets over telemetry networks.
  6. 118 DCS Distributed Control System that coordinates process control across networked controllers, operator stations, and enginee...
A variable frequency drive opened on a bench, bus capacitors and heatsink exposed, the fins carrying the dust of real service.

VFD Drive Hardware and Power Path

Phase 8 · 13 terms

Inside the drive: rectifier, DC bus and inverter, the three stages every variable frequency drive uses to rebuild the waveform a motor sees.

  1. 119 VFD Variable Frequency Drive, an electronic motor controller that varies output frequency and voltage to control AC motor op...
  2. 120 Converter / Rectifier Input power stage that converts incoming AC to DC, commonly with diodes, thyristors, or active semiconductor switches.
  3. 121 DC Bus / DC Link Intermediate DC power section between the rectifier and inverter that stores and smooths energy.
  4. 122 DC Bus Capacitor Capacitor bank that reduces DC-link ripple and supplies short-term energy to the inverter.
  5. 123 Precharge Circuit Resistor and bypass circuit that limits inrush current while the DC bus capacitors charge at power-up.
  6. 124 Inverter Output power stage that switches DC into variable-frequency, variable-voltage AC for the motor.
  7. 125 IGBT Insulated-Gate Bipolar Transistor commonly used as a high-speed power switch in a VFD inverter.
  8. 126 Braking Chopper Electronic switch that connects a braking resistor to the DC bus when bus voltage rises during deceleration.
  9. 127 Heat Sink / Cooling Fan Thermal components that remove heat from the drive power electronics.
  10. 128 Control Board Low-voltage electronics that process commands, feedback, protection, communication, and motor-control algorithms.
  11. 129 Keypad / HIM Local operator interface used to view status, edit parameters, issue commands, and read faults.
  12. 130 Control Terminals Low-voltage terminals for digital inputs, analog signals, references, relays, and auxiliary power.
  13. 131 Communication Option Card Plug-in interface that adds an industrial network or other communication protocol to the drive.
A three phase motor on a workshop pallet, a clamp meter hooked over one lead and a hand steadying the fan cowl.

VFD Ratings, Sizing, and Motor Data

Phase 9 · 16 terms

Nameplate arithmetic, where the currents, voltages and duty ratings decide whether a drive can actually run the motor you bolted it to.

  1. 132 Input Voltage / Phase AC supply voltage and phase configuration for which the drive is designed.
  2. 133 Output Current Rating Maximum continuous motor current the drive can supply under stated overload and environmental conditions.
  3. 134 Horsepower / Kilowatt Rating Nominal motor-power class for the drive, secondary to verifying motor current, duty, voltage, and overload requirements.
  4. 135 Motor Nameplate Voltage Rated motor terminal voltage entered during commissioning so the drive can establish the proper voltage and flux limits.
  5. 136 Motor Nameplate Current / FLA Rated full-load motor current used by the drive for control, overload modeling, and protection.
  6. 137 Motor Base Frequency Nameplate frequency at which the motor reaches rated voltage and normally transitions from constant-torque to field-weak...
  7. 138 Motor Nameplate Speed Rated loaded shaft speed used to estimate slip and improve motor-control accuracy.
  8. 139 Motor Power Factor Ratio related to real and apparent motor power that may be entered for motor identification or control calculations.
  9. 140 Motor Efficiency Ratio of mechanical output power to electrical input power at a stated operating point.
  10. 141 Constant Torque Rating Drive duty rating intended for loads requiring substantial torque across the speed range, commonly with a higher overloa...
  11. 142 Variable Torque Rating Drive duty rating intended mainly for centrifugal fan and pump loads whose torque demand falls rapidly with speed.
  12. 143 Overload Rating Permitted output current above the continuous rating for a stated magnitude, duration, and duty cycle.
  13. 144 SCCR Short-Circuit Current Rating, the maximum prospective fault current an assembly can safely withstand when applied as spe...
  14. 145 Enclosure Rating NEMA Type or IP code describing the environmental protection provided by the drive enclosure.
  15. 146 Ambient Temperature Surrounding air-temperature limit used to determine allowable drive loading and cooling requirements.
  16. 147 Derating Required reduction in drive output capability for conditions such as high temperature, altitude, switching frequency, or...
An oscilloscope glowing in a darkened lab, a clean waveform on its screen and probe leads clipped into the motor terminal box behind.

VFD Electrical and Motor Fundamentals

Phase 10 · 14 terms

The physics under the parameters: slip, torque, flux, and the relationship between frequency and voltage that every drive is really controlling.

  1. 148 V/Hz Ratio Volts-per-hertz relationship used below base speed to maintain suitable motor magnetic flux.
  2. 149 PWM Pulse-Width Modulation, an inverter switching method that controls effective motor voltage and frequency by varying puls...
  3. 150 Carrier Frequency Rate at which inverter power devices switch, affecting audible noise, motor heating, cable effects, drive losses, and po...
  4. 151 Output Frequency Electrical frequency commanded by the drive and applied to the motor.
  5. 152 Synchronous Speed Rotating magnetic-field speed determined by applied frequency and motor pole count, equal to 120 times hertz divided by...
  6. 153 Slip Difference between an induction motor's synchronous speed and actual rotor speed.
  7. 154 Base Speed Approximate motor speed at rated voltage and base frequency.
  8. 155 Field Weakening Operation above base frequency where voltage cannot rise proportionally, reducing available torque as speed increases.
  9. 156 Constant Torque Region Operating range, usually at or below base speed, in which rated motor flux allows approximately constant torque.
  10. 157 Constant Horsepower Region Operating range above base speed where available torque falls approximately as speed rises while power remains roughly c...
  11. 158 DC Bus Voltage Voltage on the DC link, typically near 1.35 to 1.41 times the AC line-to-line RMS voltage depending on rectifier topolog...
  12. 159 RMS Root-mean-square value used to express the heating-equivalent magnitude of an AC voltage or current.
  13. 160 Regeneration Power flow from the rotating motor and load back into the drive DC bus during overhauling or decelerating conditions.
  14. 161 Four-Quadrant Operation Capability to produce motoring and braking torque in both forward and reverse directions.
Hands adjust a small potentiometer on a drive control board laid out on an anti static mat under a bench lamp.

VFD Control Modes and Tuning

Phase 11 · 15 terms

How a drive decides what to send the motor, from plain volts per hertz up to closed loop vector control, and how each mode is tuned.

  1. 162 Open-Loop Control Motor control without direct shaft-speed or position feedback from an encoder.
  2. 163 Closed-Loop Control Motor control that uses encoder or resolver feedback to regulate shaft speed, torque, or position.
  3. 164 Scalar / V/Hz Control Control method that commands motor voltage mainly as a function of output frequency without independently regulating flu...
  4. 165 Sensorless Vector Control Control method that estimates motor flux, speed, or torque from electrical measurements and a motor model without an enc...
  5. 166 Flux Vector Control Vector method that independently regulates torque-producing and flux-producing current components for improved dynamic a...
  6. 167 Torque Control Operating mode in which motor torque is the primary commanded variable or regulated limit.
  7. 168 Speed Control Operating mode in which motor speed or frequency is the primary regulated variable.
  8. 169 Autotune / Motor Identification Commissioning routine that measures or estimates motor parameters used by the drive's control model.
  9. 170 Slip Compensation Automatic frequency adjustment that reduces induction-motor speed change as load torque changes.
  10. 171 Torque Boost Additional low-frequency voltage used to compensate stator resistance and improve starting or low-speed torque.
  11. 172 Current Limit Control function that restricts motor current and may reduce acceleration or output frequency to avoid an overcurrent tr...
  12. 173 Stall Prevention Drive response that modifies acceleration, deceleration, or speed to keep current or DC-bus voltage within limits.
  13. 174 Flying Start / Catch on the Fly Function that detects the speed and direction of a spinning motor before smoothly taking control.
  14. 175 Skip Frequency Configured speed band the drive avoids during steady operation to reduce mechanical resonance.
  15. 176 Internal PID Drive-based proportional-integral-derivative controller that adjusts motor speed to regulate process feedback.
A pendant control station beside a machine, green and red pushbuttons worn smooth and its cable curling down out of frame.

VFD Commands, References, and Stopping

Phase 12 · 18 terms

Starting, referencing and stopping, including the several very different things a drive can mean by the word stop.

  1. 177 Run Command Signal or network command that requests the drive to operate when all enables and permissives are satisfied.
  2. 178 Run Enable Hardware or logic condition that must be present before the drive will accept a run command.
  3. 179 Forward / Reverse Direction command that selects the sign of motor rotation subject to configuration and interlocks.
  4. 180 Speed Reference Commanded speed or frequency value received from the keypad, analog input, preset, PID, or network.
  5. 181 Minimum / Maximum Frequency Configured lower and upper limits applied to the commanded drive output frequency.
  6. 182 Acceleration Time Configured time for the drive to ramp between defined low and high frequency reference points.
  7. 183 Deceleration Time Configured time for the drive to ramp between defined high and low frequency reference points.
  8. 184 S-Curve Ramp profile that rounds acceleration changes to reduce mechanical shock and jerk.
  9. 185 Jog Temporary command that runs the motor at a dedicated low speed for setup or positioning.
  10. 186 Ramp Stop Stop method that reduces commanded frequency along a programmed deceleration ramp.
  11. 187 Coast Stop Stop method that disables inverter output and lets the motor slow according to load inertia and friction.
  12. 188 DC Injection Braking Stopping or holding method that applies DC current to the motor stator to create braking torque without regeneration.
  13. 189 Dynamic Braking Method that dissipates regenerated motor energy in a resistor connected to the DC bus through a braking chopper.
  14. 190 Braking Resistor Resistor sized to absorb regenerated energy and limit DC-bus voltage during dynamic braking.
  15. 191 Two-Wire Control Maintained-contact control scheme in which the run input remains asserted while operation is requested.
  16. 192 Three-Wire Control Momentary start and stop control scheme with drive logic that seals in the run state.
  17. 193 Local / Remote Selection between commands and references from the drive interface and those from external terminals or communications.
  18. 194 Preset Speed Stored frequency or speed reference selected by digital inputs or network commands.
A shielded motor cable enters a drive through a metal gland, its braid fanned out and clamped to the grounding bar.

VFD Power Quality, Wiring, and Motor Protection

Phase 13 · 18 terms

Harmonics, reflected waves, shielded cable and bearing currents: the side effects a drive inflicts on everything around it.

  1. 195 Harmonics Current or voltage components at integer multiples of the fundamental frequency that distort the supply waveform.
  2. 196 THD Total Harmonic Distortion, a ratio that summarizes harmonic content relative to the fundamental component.
  3. 197 Six-Pulse Rectifier Common three-phase diode bridge with six switching pulses per line cycle and characteristic input-current harmonics.
  4. 198 Twelve-Pulse / Eighteen-Pulse Drive Multipulse rectifier arrangement using phase-shifted transformer windings to reduce selected line harmonics.
  5. 199 Active Front End (AFE) Controlled rectifier that can regulate the DC bus, reduce line-current distortion, and often return regenerated power to...
  6. 200 Line Reactor Series input inductor that reduces current peaks, line disturbances, and some harmonic current while adding impedance.
  7. 201 DC Link Choke Inductor in the DC link used to smooth current and reduce stress and line harmonics.
  8. 202 Load Reactor Series output inductor that reduces motor current rise, voltage stress, and some long-cable effects.
  9. 203 DV/dt Filter Output filter that reduces the rate of voltage change and peak motor-terminal voltage from PWM switching.
  10. 204 Sine-Wave Filter Output filter that converts the PWM waveform toward a sinusoidal motor voltage.
  11. 205 Reflected Wave Cable-transmission effect that can produce high motor-terminal voltage peaks when PWM pulses reflect on long leads.
  12. 206 Common-Mode Voltage Voltage shared by motor phases relative to ground that can drive leakage and bearing currents.
  13. 207 Bearing Current Unwanted current through motor bearings caused by common-mode voltage, shaft voltage, or grounding paths.
  14. 208 Shaft Grounding Ring Conductive device that provides a low-impedance path from the motor shaft to frame to reduce bearing discharge damage.
  15. 209 Shielded VFD Cable Motor cable designed with suitable insulation and a continuous low-impedance shield or armor for PWM drive service.
  16. 210 Bonding Low-impedance connection of drive, enclosure, cable shield, and motor frame to control fault and high-frequency currents...
  17. 211 Output Contactor Contactor between drive and motor that must be applied and sequenced only as permitted by the drive manufacturer.
  18. 212 Bypass Power and control arrangement that allows a motor to operate across the line when the drive is isolated or unavailable.
A single red indicator burns on a drive front panel in a darkened cabinet, a torch beam raking low across the heatsink fins beside it.

VFD Safety, Faults, and Diagnostics

Phase 14 · 14 terms

What a drive does when it trips, what the fault codes are telling you, and how safe torque off stops the motor without killing the panel.

  1. 213 STO Safe Torque Off, a certified drive safety function that prevents torque-producing energy without serving as electrical i...
  2. 214 Motor Electronic Overload Drive thermal model that estimates motor heating from current, speed, time, and configured motor data.
  3. 215 Overcurrent Fault Trip caused when output current exceeds the drive's instantaneous protection threshold.
  4. 216 DC Bus Overvoltage Trip caused when DC-link voltage rises above its safe limit, often during rapid deceleration or high line voltage.
  5. 217 DC Bus Undervoltage Trip or warning caused when DC-link voltage falls below the level needed for reliable operation.
  6. 218 Ground Fault Detected unintended current path from a drive output or motor circuit to ground.
  7. 219 Input Phase Loss Loss or severe imbalance of an incoming AC phase that increases rectifier and DC-bus stress.
  8. 220 Output Phase Loss Detected open motor phase or severe output-current imbalance between phases.
  9. 221 Overtemperature Trip caused when measured drive, heat-sink, or motor temperature exceeds a configured safe limit.
  10. 222 Motor Thermistor / PTC Temperature-sensitive device embedded in a motor and connected to the drive or protection relay.
  11. 223 Fault Protective condition that normally stops or inhibits drive output and requires the cause to clear before reset.
  12. 224 Alarm / Warning Abnormal condition reported by the drive that may allow continued operation for a limited or indefinite time.
  13. 225 Fault History Stored record of recent trips and operating data used to identify recurring causes.
  14. 226 Auto Restart Configured function that attempts to resume operation after selected faults and must be evaluated for machine safety.
A communications card slides into a drive's expansion slot, its edge connector and a fieldbus plug steady in the other hand.

VFD Parameters and Communications

Phase 15 · 6 terms

The parameter set itself, and the network words a controller uses to read and write it while the machine is running.

  1. 227 Parameter Stored drive setting that defines ratings, control behavior, I/O functions, limits, or communications.
  2. 228 Parameter Group Vendor-defined category used to organize related drive settings.
  3. 229 Application Macro Preset group of parameter assignments for a common control arrangement or machine application.
  4. 230 Control Word / Status Word Bit-mapped network command and feedback data used to control and monitor a drive.
  5. 231 Reference / Feedback Word Network data values used to send a speed or torque command and return actual operating feedback.
  6. 232 Modbus RTU / Modbus TCP Register-based serial or Ethernet protocols commonly used to command, monitor, and configure drives.
A workshop shelf lined with drive units side by side, a soft starter, a compact drive and a servo amplifier, each with its own fins and connectors.

VFD Related Drive Terms

Phase 16 · 8 terms

The drive family's wider vocabulary, from soft starters and servo drives to the regenerative units people also call a drive.

  1. 233 VSD Variable Speed Drive, a broad term for equipment that controls prime-mover or motor speed.
  2. 234 ASD Adjustable Speed Drive, another broad term for a motor-speed control system.
  3. 235 VVVF Variable Voltage Variable Frequency, a descriptive term for a common AC drive output method.
  4. 236 AC Drive Common industry name for an electronic drive that controls an AC motor.
  5. 237 Soft Starter Solid-state starter that limits motor starting voltage and current but does not provide continuous variable-frequency sp...
  6. 238 Inverter-Duty Motor Motor designed or rated to tolerate specified PWM voltage stress, thermal conditions, and operating-speed range.
  7. 239 Regenerative Drive Drive capable of returning braking energy from the DC bus to the AC supply.
  8. 240 Common DC Bus Architecture in which multiple drive sections share one DC link so energy can be exchanged between axes or supplied by a...