Corpus sync: neutrality remakes, note hygiene, datasheet relocation, transformer-split cross-refs
---
title: Low-Voltage Variable Frequency Drives
category: Electrical
toc_depth: 3
description: >
− When to use: Individually mounted, enclosed pulse-width-modulated (PWM)
− variable frequency drives rated 600 V and below, specified under Division 26
− for speed control of three-phase AC induction and permanent-magnet motors in
− non-HVAC applications — process pumps and fans, compressors, conveyors,
− mixers, water and wastewater treatment, and general industrial, institutional,
− and municipal motor loads. Covers fractional through 500 HP, wall- and
− floor-mount construction, NEMA 1 through 4X enclosures, indoor and outdoor
− service, variable- and constant-torque duty, input protection, harmonic
− mitigation, bypass, network communication, output filtering, and acceptance
− testing.
− Not intended for: HVAC fan and pump drives specified under Division 23 (see
− [[sync/hvac-variable-frequency-drives]]); VFD units furnished as plug-in
− bucket contents in a motor control center assembly (see
− [[sync/motor-control-centers]]); medium-voltage drives above 600 V; drives
− integral to factory-packaged process equipment governed by their equipment
− specification; motor-circuit and output conductors (see
− [[sync/conductors-and-cables]]); and the feeder or branch-circuit panelboard
− upstream of the drive (see [[sync/low-voltage-panelboards]]).
+ When to use: Individually mounted, enclosed pulse-width-modulated (PWM) variable frequency drives rated 600 V and below, specified under the electrical division for speed control of three-phase AC induction and permanent-magnet motors in non-HVAC applications — process pumps and fans, compressors, conveyors, mixers, water and wastewater treatment, and general industrial, institutional, and municipal motor loads. Covers fractional through 500 HP, wall- and floor-mount construction, NEMA 1 through 4X enclosures, indoor and outdoor service, variable- and constant-torque duty, input protection, harmonic mitigation, bypass, network communication, output filtering, and acceptance testing.
+ Not intended for: HVAC fan and pump drives specified under the mechanical division (see [[sync/hvac-variable-frequency-drives]]); VFD units furnished as plug-in bucket contents in a motor control center assembly (see [[sync/motor-control-centers]]); medium-voltage drives above 600 V; drives integral to factory-packaged process equipment governed by their equipment specification; motor-circuit and output conductors (see [[sync/conductors-and-cables]]); and the feeder or branch-circuit panelboard upstream of the drive (see [[sync/panelboards]]).
---
…20 unchanged lines
## Conductors and cables between the drive output and the motor terminals are excluded; their sizing, insulation class, and shielding are governed by [[sync/conductors-and-cables]]. {note}
−## Feeder and branch-circuit panelboard distribution upstream of the drive is excluded and is governed by [[sync/low-voltage-panelboards]]. {note}
+## Feeder and branch-circuit panelboard distribution upstream of the drive is excluded and is governed by [[sync/panelboards]]. {note}
# Referenced Standards {toc}
…6 unchanged lines
|----------|-------|
| UL 61800-5-1 | Adjustable Speed Electrical Power Drive Systems — Electrical, Thermal and Energy Safety Requirements |
−| NEMA ICS 7-2020 | Adjustable-Speed Drives |
−| NEMA 250-2020 | Enclosures for Electrical Equipment (1000 Volts Maximum) |
−| IEEE 519-2022 | Standard for Harmonic Control in Electric Power Systems |
−| NFPA 70 (NEC) 2023 | National Electrical Code (Articles 409 and 430) |
−| NEMA MG 1-2021 | Motors and Generators (Part 31) |
+| UL 508A | Industrial Control Panels |
+| NFPA 70 | National Electrical Code (Articles 409 and 430) |
+| NEMA ICS 7 | Adjustable-Speed Drives |
+| NEMA 250 | Enclosures for Electrical Equipment (1000 Volts Maximum) |
+| NEMA MG 1 | Motors and Generators (Part 31 — Definite-Purpose Inverter-Fed Motors) |
+| IEEE 519 | Standard for Harmonic Control in Electric Power Systems |
| IEC 61800-3 | Adjustable Speed Electrical Power Drive Systems — EMC Requirements and Test Methods |
−| IEC 61800-9-2 | Adjustable Speed Electrical Power Drive Systems — Energy Efficiency Indicators for Power Drive Systems |
| IEC 61800-5-2 | Adjustable Speed Electrical Power Drive Systems — Functional Safety Requirements |
−| NETA ATS-2021 | Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems |
−| ASHRAE 90.1-2022 | Energy Standard for Buildings Except Low-Rise Residential Buildings |
−| ASCE 7-22 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
+| IEC 61800-9-2 | Adjustable Speed Electrical Power Drive Systems — Energy Efficiency Indicators for Power Drive Systems |
+| NETA ATS | Standard for Acceptance Testing Specifications for Electrical Power Equipment and Systems |
+| ASHRAE 90.1 | Energy Standard for Buildings Except Low-Rise Residential Buildings |
+| ASCE 7 | Minimum Design Loads and Associated Criteria for Buildings and Other Structures |
−## UL 508C, the historical listing standard for power conversion equipment, was withdrawn and superseded by UL 61800-5-1 effective February 28, 2020; specifications and submittals shall reference UL 61800-5-1 and shall not cite UL 508C. {note}
+## UL 508C, the historical listing standard for power conversion equipment, was withdrawn and superseded by UL 61800-5-1 effective February 28, 2020. {note}
+## Specifications and submittals shall reference UL 61800-5-1 and shall not cite UL 508C.
+
+## The three IEC 61800 parts referenced above have no ANSI or UL equivalent for EMC categories, functional-safety integrity levels, or power drive system efficiency classes, and US drive manufacturers publish these designations in their North American catalog data; they are cited here for that reason. {note}
+
# Submittals {toc}
…6 unchanged lines
- Wiring and interconnection diagrams showing power, control, and network terminations.
- Drive schedule correlating each tag to motor nameplate data, duty type, enclosure type, and mitigation and bypass options.
−- IEEE 519-2022 harmonic analysis demonstrating compliance at the designated point of common coupling.
+- IEEE 519 harmonic analysis demonstrating compliance at the designated point of common coupling.
- Short-circuit current rating (SCCR) documentation for each enclosed drive assembly.
- Seismic anchorage calculations and certification for floor-mounted enclosures where required by the seismic design category.
…7 unchanged lines
- Wiring and interconnection diagrams
- Drive schedule (motor data, duty, enclosure)
− - IEEE 519-2022 harmonic analysis
+ - IEEE 519 harmonic analysis
- SCCR documentation
- Seismic anchorage calculations and certification
…3 unchanged lines
- Wiring and interconnection diagrams
- Drive schedule (motor data, duty, enclosure)
− - IEEE 519-2022 harmonic analysis
+ - IEEE 519 harmonic analysis
- SCCR documentation
```
−### Action submittals shall be coordinated with the building automation or process control submittal so that the network protocol matches the controlling system before the drives are released. {note}
−
## Informational Submittals {toc}
…23 unchanged lines
### The Contractor shall submit the following closeout submittals before final acceptance:
−- Field acceptance test reports per NETA ATS-2021, including insulation resistance and functional verification.
+- Field acceptance test reports per NETA ATS, including insulation resistance and functional verification.
- As-left parameter records for each drive, listing every adjusted setting.
- Operation and maintenance manuals, including troubleshooting and fault-code references.
…17 unchanged lines
# Quality Assurance {toc}
−## Each drive shall be listed by a Nationally Recognized Testing Laboratory to UL 61800-5-1 and shall bear the listing mark. {note}
+## Each drive shall be listed by a Nationally Recognized Testing Laboratory to UL 61800-5-1.
+## Each drive shall bear the listing mark of the Nationally Recognized Testing Laboratory that listed it.
+
## The manufacturer shall regularly produce adjustable-speed drives of the type and rating specified, with a documented production history of not less than five years.
−## The complete enclosed drive assembly, including integral disconnect, fusing, reactors, and bypass where furnished, shall carry a marked short-circuit current rating equal to or greater than the available fault current at the point of installation.
−
## The drive shall be designed and rated in accordance with NEMA ICS 7 for adjustable-speed drives.
−## Where the drive is furnished as an enclosed industrial control panel, the assembly shall comply with the applicable construction and marking requirements of NEC Article 409. {note}
+## Where the drive is furnished as an enclosed industrial control panel, the assembly shall comply with the applicable construction and marking requirements of NEC Article 409 and UL 508A.
−## Field test personnel shall be qualified to perform acceptance testing in accordance with NETA ATS-2021.
+## Field test personnel shall be qualified to perform acceptance testing in accordance with NETA ATS.
# Ratings and Performance {toc}
## Voltage and Horsepower {toc}
−### The drive system voltage and horsepower or kW rating shall match the connected motor nameplate, accounting for service factor where the motor is operated continuously above nameplate. {note}
+### The drive system voltage and horsepower or kW rating shall match the connected motor nameplate, accounting for service factor where the motor is operated continuously above nameplate.
### Each drive shall be rated for continuous operation at the connected motor full-load current at the installed ambient and altitude.
+### The drive system voltage shall be as indicated in the datasheet.
+
```datasheet
label: System voltage
−type: radio
+type: range
unit: V
+drawing_ref: "one-line diagram"
options:
− - "208"
− - "240"
− - "480"
− - "600"
−default: "480"
+ min: 208
+ max: 600
+ setpoints: [208, 240, 480, 600]
+default: deferred
```
+### The drive continuous output rating shall be as indicated in the datasheet.
+
```datasheet
label: Drive continuous output rating
type: range
unit: HP
−min: 0.5
−max: 500
−step: 0.5
−default: 25
+drawing_ref: "motor and drive schedule"
+options:
+ min: 0.5
+ max: 500
+ step: 0.5
+default: deferred
```
+### The maximum rated output frequency shall be as indicated in the datasheet.
+
```datasheet
−label: Rated output frequency range
+label: Maximum rated output frequency
type: range
unit: Hz
−min: 0
−max: 120
−step: 1
−setpoints: [0, 60, 120]
+options:
+ min: 30
+ max: 400
+ setpoints: [30, 50, 60, 90, 120, 200, 400]
default: 60
```
+### 60 Hz is the North American norm for a motor operated at its nameplate base speed and is the datasheet default; 50 Hz base-speed motors and over-speed applications running above base frequency are both real selections, and a drive operated above base frequency delivers constant horsepower with falling torque. {note}
+
## Duty Type and Overload {toc}
−### The drive overload rating shall match the load torque characteristic. Variable-torque loads (centrifugal pumps and fans) require only modest overload; constant-torque and high-starting-torque loads (conveyors, positive-displacement pumps, compressors, mixers) demand sustained and instantaneous overload margin. {note}
+### The drive overload rating shall match the load torque characteristic. Variable-torque loads (centrifugal pumps and fans) require only modest overload; constant-torque and high-starting-torque loads (conveyors, positive-displacement pumps, compressors, mixers) demand sustained and instantaneous overload margin.
−### Applying a variable-torque-rated drive to a constant-torque load causes nuisance overload trips or drive damage under high starting torque; the duty type shall be confirmed against the actual load before the drive is sized. {note}
+### Applying a variable-torque-rated drive to a constant-torque load causes nuisance overload trips or drive damage under high starting torque. {note}
+### The duty type shall be confirmed against the actual load torque characteristic before the drive is sized.
+
### A drive serving a variable-torque load shall provide not less than 110% of rated output current for 60 seconds.
…2 unchanged lines
### A drive serving a high-starting-torque load shall provide not less than 150% of rated output current for 60 seconds and 175% instantaneous current.
+### The duty type shall be as indicated in the datasheet.
+
```datasheet
label: Duty type
…3 unchanged lines
- Constant torque (150% for 60 s)
- Heavy duty / high starting torque (150% for 60 s, 175% instantaneous)
−default: Constant torque (150% for 60 s)
```
+### The duty type is a property of the driven machine rather than of the drive, and this Standard covers centrifugal and positive-displacement loads in comparable numbers, so the field carries no default. {note}
+
## Efficiency {toc}
−### The complete power drive system (motor plus drive) shall meet the efficiency provisions applicable to the project under ASHRAE 90.1, and variable-speed control thresholds for pumps and fans shall be documented in the submittal. {note}
+### The complete power drive system (motor plus drive) shall meet the efficiency provisions applicable to the project under ASHRAE 90.1.
−### The drive shall meet not less than the IE2 efficiency class for power drive systems defined in IEC 61800-9-2.
+### The variable-speed control thresholds applied to pumps and fans under ASHRAE 90.1 shall be documented in the action submittal.
+### The drive shall meet not less than the IEC 61800-9-2 power drive system efficiency class indicated in the datasheet.
+
```datasheet
label: Minimum power drive system efficiency class (IEC 61800-9-2)
…5 unchanged lines
```
+### IE2 is the datasheet default because it is the class the current generation of general-purpose drives reaches without a cost premium; IE1 remains available for retrofit and replacement-in-kind work where an existing drive family must be matched. {note}
+
# Environmental and Service Conditions {toc}
## Enclosure Type {toc}
−### The enclosure type shall be selected for the actual installed environment per NEMA 250; enclosure cost, size, and cooling capacity differ substantially between types, so over- and under-specification both carry consequences. {note}
+### The drive enclosure type shall be selected for the actual installed environment per NEMA 250.
−### Specifying a NEMA 1 drive where the environment exposes it to water spray, washdown, dust, or condensation causes premature failure and warranty dispute; the enclosure rating shall reflect the worst-case service condition at the device location. {note}
+### Enclosure cost, size, and cooling capacity differ substantially between types, so over- and under-specification both carry consequences. Specifying a NEMA 1 drive where the environment exposes it to water spray, washdown, dust, or condensation causes premature failure and warranty dispute. {note}
−### The drive enclosure shall be of the type listed below and shall maintain its rating with all field-installed conduit entries and accessories in place.
+### The enclosure rating shall reflect the worst-case service condition at the device location.
+### The drive enclosure shall be as indicated in the datasheet and shall maintain its rating with all field-installed conduit entries and accessories in place.
+
```datasheet
label: Enclosure type (NEMA 250)
…5 unchanged lines
- NEMA 4 (washdown, hose-directed water)
- NEMA 4X (corrosive, stainless or nonmetallic)
−default: NEMA 1 (indoor, clean)
```
+### This Standard covers clean indoor electrical rooms, process areas subject to washdown, and outdoor installations in comparable numbers, so no enclosure type is correct for every project and the field carries no default. {note}
+
+### The mounting configuration shall be as indicated in the datasheet.
+
```datasheet
label: Mounting configuration
type: radio
+drawing_ref: "electrical plan"
options:
- Wall mount
- Floor mount (freestanding)
−default: Wall mount
+default: deferred
```
…4 unchanged lines
### Above 3300 ft a typical drive loses approximately 1% of rated current per 330 ft of additional elevation; high-altitude sites are frequently overlooked and require derating or cooling accessories. {note}
−### The drive shall be rated for the maximum ambient temperature at its installed location without exceeding its current rating; where the ambient exceeds the standard rating, the drive shall be upsized or provided with supplemental cooling.
+### The drive shall be rated for the maximum design ambient temperature indicated in the datasheet without exceeding its current rating.
−### The drive shall be derated or otherwise compensated for installations above 3300 ft so that it delivers full motor full-load current at the site elevation.
+### Where the ambient exceeds the drive's standard rating, the drive shall be upsized or provided with supplemental cooling.
```datasheet
label: Maximum design ambient temperature
type: range
unit: °C
−min: 0
−max: 55
−step: 5
−setpoints: [40, 45, 50]
+options:
+ min: 0
+ max: 55
+ step: 5
+ setpoints: [40, 45, 50, 55]
default: 40
```
+### 40°C is the standard rating reference for enclosed drives and is the datasheet default; it is a rating basis rather than a measured room temperature, and it is raised only where the installed location is known to run hotter. {note}
+
+### The drive shall be derated or otherwise compensated for the installation altitude indicated in the datasheet so that it delivers full motor full-load current at the site elevation.
+
```datasheet
label: Installation altitude
type: range
unit: ft
−min: 0
−max: 12000
−step: 100
−setpoints: [3300, 6600, 10000]
−default: 3300
+options:
+ min: 0
+ max: 12000
+ step: 100
+ setpoints: [3300, 6600, 10000, 12000]
```
+### Site elevation is a project fact rather than a specification choice, and a wrong assumed elevation silently undersizes the drive, so the field carries no default. {note}
+
# Input Power and Protection {toc}
…2 unchanged lines
### Adjustable-speed drives are governed by NEC Article 430 Part X; the supply conductors are sized at not less than 125% of the rated drive input current, which differs from a standard motor branch circuit sized on motor full-load current. {note}
−### Drive input overcurrent protection sized on the drive input current rather than the motor full-load current per NEC 430.52 is a common error that leaves the drive either over-fused or under-fused; the protective device shall be coordinated to the rule that applies to the installation. {note}
+### Drive input overcurrent protection sized on the drive input current rather than the motor full-load current per NEC 430.52 is a common error that leaves the drive either over-fused or under-fused. {note}
+### The branch-circuit protective device ahead of the drive shall be coordinated to the sizing rule of NEC Article 430 that applies to the installation.
+
### Branch-circuit short-circuit and ground-fault protection ahead of the drive shall be selected and sized in accordance with NEC Article 430.
### A disconnecting means shall be provided for the drive in accordance with NEC Article 430, located within sight of the drive or provided with a lockable disconnect.
−### The marked short-circuit current rating of the enclosed drive assembly shall equal or exceed the available fault current at the point of installation.
+### The integral input disconnect arrangement shall be as indicated in the datasheet.
```datasheet
label: Integral input disconnect
type: radio
+drawing_ref: "one-line diagram"
options:
- None (external disconnect by others)
- Non-fusible disconnect switch
- Fusible disconnect switch
- Molded-case circuit breaker
−default: Fusible disconnect switch
+default: deferred
```
+### The marked short-circuit current rating of the enclosed drive assembly, including integral disconnect, fusing, reactors, and bypass where furnished, shall equal or exceed the available fault current at the point of installation.
+
```datasheet
label: Minimum assembly short-circuit current rating (SCCR)
−type: radio
+type: range
unit: kA
options:
− - "5"
− - "10"
− - "14"
− - "18"
− - "22"
− - "42"
− - "65"
− - "100"
−default: "65"
+ min: 5
+ max: 200
+ setpoints: [5, 10, 14, 18, 22, 25, 30, 35, 42, 50, 65, 100, 200]
```
+### The required rating is the first standard interrupting rating at or above the available fault current at the drive, which is an output of the project's short-circuit study, so the field carries no default. {note}
+
## Input Power Quality Accessories {toc}
### Input accessories protect the drive from supply transients and reduce conducted disturbances back onto the source; the complement is selected from the supply impedance and the sensitivity of co-located equipment. {note}
−### Each drive shall be provided with the input power-quality accessories listed below, coordinated with the harmonic mitigation strategy so that protective devices are not duplicated.
+### Each drive shall be provided with the input power-quality accessories indicated in the datasheet, coordinated with the harmonic mitigation method so that reactors and chokes are not duplicated.
```datasheet
…13 unchanged lines
## The drive rectifier draws nonsinusoidal current that injects harmonic distortion onto the supply; without a study and a specified mitigation method, the contractor quotes the cheapest (no mitigation) option, risking utility non-compliance and interference with neighboring loads. {note}
−## Harmonic mitigation shall be engineer-specified based on an IEEE 519-2022 analysis at the point of common coupling; it shall not be left to the contractor to determine in the field. {note}
+## The harmonic mitigation method shall be specified by the Engineer of Record and shall not be left to the Contractor to determine in the field.
−## An IEEE 519-2022 harmonic analysis shall be performed for the installation and shall demonstrate that current and voltage distortion at the designated point of common coupling are within the limits of the standard.
+## An IEEE 519 harmonic analysis shall be performed for the installation and shall demonstrate that current and voltage distortion at the designated point of common coupling are within the limits of the standard.
−## The harmonic mitigation method selected shall achieve the IEEE 519-2022 distortion limits at the point of common coupling under the project's worst-case operating condition.
+## The harmonic mitigation method selected shall achieve the IEEE 519 distortion limits at the point of common coupling under the project's worst-case operating condition.
−## The point of common coupling for the analysis shall be the location designated on the drawings: [[drawing: PCC location on one-line]].
+## The point of common coupling for the analysis shall be [[drawing: as indicated on the one-line diagram]].
+## The harmonic mitigation method shall be as indicated in the datasheet.
+
```datasheet
label: Harmonic mitigation method
…9 unchanged lines
- 18-pulse drive topology
- Active front end (regenerative)
−default: 5% AC line reactor
```
+## The mitigation method is an output of the project's IEEE 519 study, and a small drive on a stiff service may legitimately need none while a drive farm on a generator-backed bus may need an active front end, so the field carries no default. {note}
+
+## Current distortion at the point of common coupling shall not exceed the total demand distortion limit given by IEEE 519 for the short-circuit ratio at that point, and shall not exceed the limit indicated in the datasheet where a more stringent limit is required.
+
```datasheet
label: Maximum total demand distortion (current) at PCC
type: range
unit: "%"
−min: 5
−max: 20
−step: 1
−setpoints: [5, 8, 12, 15, 20]
−default: 8
+options:
+ min: 5
+ max: 20
+ step: 1
+ setpoints: [5, 8, 12, 15, 20]
```
+## Voltage distortion at the point of common coupling shall not exceed the total harmonic distortion limit given by IEEE 519 for the voltage level at that point, and shall not exceed the limit indicated in the datasheet where a more stringent limit is required.
+
```datasheet
label: Maximum total harmonic voltage distortion at PCC
type: range
unit: "%"
−min: 3
−max: 8
−step: 1
−setpoints: [3, 5, 8]
−default: 5
+options:
+ min: 1.5
+ max: 8
+ setpoints: [1.5, 2.5, 3, 5, 8]
```
+## Both distortion limits are read from the IEEE 519 tables for the actual short-circuit ratio and system voltage at the point of common coupling, so neither field carries a default; the datasheet entry records the value the study establishes or a stricter owner limit. {note}
+
# Output and Motor Compatibility {toc}
…2 unchanged lines
### A PWM drive produces fast-rising voltage pulses; on long motor cables these pulses reflect at the motor terminals and can double, producing peak voltages that stress the motor insulation. {note}
−### NEMA MG 1 Part 31 inverter-duty motors withstand up to 1600 V peak, but non-inverter-duty motors may not; the threshold cable length depends on the drive switching frequency, so the maximum cable length and required output filter shall be established from the actual installation rather than omitted. {note}
+### NEMA MG 1 Part 31 inverter-duty motors withstand up to 1600 V peak, but non-inverter-duty motors may not, and the threshold cable length depends on the drive switching frequency. {note}
### Failing to specify a motor cable length limit or output filter is a frequent omission; the resulting reflected-wave overvoltage can exceed the motor insulation rating and cause early winding failure. {note}
…3 unchanged lines
### Where the connected motor is not rated for inverter duty, output filtering shall be provided to limit the terminal peak voltage and rate of voltage rise to within the motor insulation withstand.
−### The output filter type shall be selected to suit the cable length and motor rating per the table below.
+### The output filter shall be as indicated in the datasheet.
```datasheet
…5 unchanged lines
- Output line reactor
- Sine-wave filter
−default: None (bare cable, short run)
```
+### The filter follows from the compatibility analysis — cable length, carrier frequency, and whether the motor is inverter-duty rated — so no filter selection is correct for every project and the field carries no default. {note}
+
+### The maximum unfiltered motor cable length shall be as indicated in the datasheet.
+
```datasheet
label: Maximum motor cable length (unfiltered)
type: range
unit: ft
−min: 25
−max: 1000
−step: 25
−setpoints: [50, 100, 200, 400]
−default: 100
+options:
+ min: 25
+ max: 1000
+ step: 25
+ setpoints: [25, 50, 100, 200, 400, 600, 1000]
```
+### The cable length limit is a property of the installed run and of the drive and motor pair, so the field carries no default and is filled from the compatibility analysis. {note}
+
+### The drive carrier frequency shall be as indicated in the datasheet.
+
```datasheet
label: Drive carrier (switching) frequency
type: range
unit: kHz
−min: 1
−max: 16
−step: 1
−setpoints: [2, 4, 8]
−default: 4
+options:
+ min: 1
+ max: 16
+ step: 1
+ setpoints: [1, 2, 4, 8, 12, 16]
```
+### The manufacturer's standard carrier frequency for the drive rating is acceptable; a higher carrier reduces audible motor noise but shortens the permissible cable length and derates the drive, and a lower carrier does the reverse. The as-left carrier frequency shall be recorded in the parameter record submitted at closeout.
+
## Motor Protection {toc}
…6 unchanged lines
## A bypass connects the motor directly across the line when the drive is unavailable, preserving operation of life-safety and process-critical loads; it is selected from the criticality of the load. {note}
−## In bypass mode the motor runs across the line at full speed, so motor running overload protection must be provided in the bypass path separately from the drive's electronic overload; many specifications omit this and the omission surfaces at startup. {note}
+## In bypass mode the motor runs across the line at full speed, so the drive's electronic overload is out of the circuit — an omission that commonly surfaces at startup. {note}
−## Where bypass is specified, the bypass arrangement shall be provided as listed below.
+## The bypass arrangement shall be as indicated in the datasheet.
−## Where bypass is provided, a motor running overload relay shall be furnished in the bypass path to protect the motor when it is operated across the line.
−
−## Where automatic bypass is provided, an output contactor and transfer logic shall be furnished to transfer the motor between drive and line operation.
−
```datasheet
label: Bypass configuration
…6 unchanged lines
```
+## Most process drives are not bypassed, because bypass operation runs the load at full speed and defeats the reason the drive was installed; bypass is reserved for loads whose continued operation matters more than speed control, so the field defaults to none. {note}
+
+## Where bypass is provided, a motor running overload relay shall be furnished in the bypass path to protect the motor when it is operated across the line.
+
+## Where automatic bypass is provided, an output contactor and transfer logic shall be furnished to transfer the motor between drive and line operation.
+
# Control and Communication {toc}
…2 unchanged lines
### The drive shall provide a control terminal strip for speed reference, start and stop, and fault signaling.
−### The drive shall accept an analog speed reference signal of the type listed below.
−
### The drive shall provide an operator keypad with local and remote control selection and fault display.
+### The drive shall accept the analog speed reference signal indicated in the datasheet.
+
```datasheet
label: Analog speed reference input
…2 unchanged lines
- 0-10 VDC
- 4-20 mA
+ - 0-20 mA
+ - ±10 VDC (bidirectional)
+ - None — speed commanded over the network
default: 4-20 mA
```
+### A 4-20 mA current loop is the default because it is immune to the voltage drop and induced noise that corrupt a voltage reference over the cable lengths typical of process installations. {note}
+
+### The drive shall be furnished with not less than the discrete input and relay output complement indicated in the datasheet.
+
```datasheet
label: Discrete (digital) input count
type: range
unit: inputs
−min: 2
−max: 12
−step: 1
−default: 6
+options:
+ min: 2
+ max: 12
+ step: 1
```
…2 unchanged lines
type: range
unit: outputs
−min: 1
−max: 6
−step: 1
−default: 2
+options:
+ min: 1
+ max: 6
+ step: 1
```
+### The manufacturer's standard onboard input and output complement is acceptable for a drive under simple start/stop and speed-reference control; an explicit count is entered only where the sequence of operations needs more points than the base drive provides. {note}
+
## Network Communication {toc}
−### The fieldbus protocol shall match the building automation system or SCADA system; specifying a protocol the control system does not speak forces field rewiring or protocol converters after installation. {note}
+### The fieldbus protocol shall match the building automation system or SCADA system; specifying a protocol the control system does not speak forces field rewiring or protocol converters after installation.
−### The network protocol shall be coordinated with the building automation or process control contractor before the drives are released for fabrication. {note}
+### The network protocol shall be coordinated with the building automation or process control contractor before the drives are released for fabrication.
−### The drive shall be furnished with the network communication interface listed below, with all addressing and configuration coordinated with the controlling system.
+### The drive shall be furnished with the network communication interface indicated in the datasheet, with all addressing and configuration coordinated with the controlling system.
```datasheet
…7 unchanged lines
- BACnet/IP
- PROFIBUS
− - EtherNet/IP
- PROFINET
−default: BACnet/IP
+ - EtherNet/IP
+ - DeviceNet
+ - EtherCAT
```
+### The protocol is fixed by the controlling system rather than by the drive — BACnet dominates building automation, EtherNet/IP and PROFINET dominate industrial control, and Modbus persists across both — so the field carries no default. {note}
+
## Functional Safety {toc}
−### Machinery applications increasingly require a SIL-rated Safe Torque Off function under machinery safety standards and lockout/tagout practice; retrofitting STO after equipment selection is costly, so the requirement shall be established at specification. {note}
+### Machinery applications increasingly require a SIL-rated Safe Torque Off function under machinery safety standards and lockout/tagout practice, and retrofitting STO after equipment selection is costly. {note}
−### Where Safe Torque Off is specified, the drive shall provide a Safe Torque Off function listed to IEC 61800-5-2 at the safety integrity level required for the application.
+### The Safe Torque Off requirement shall be established at specification rather than deferred to the drive submittal.
+### Where Safe Torque Off is specified, the drive shall provide a Safe Torque Off function listed to IEC 61800-5-2 at the safety integrity level indicated in the datasheet.
+
```datasheet
label: Safe Torque Off (STO) per IEC 61800-5-2
…3 unchanged lines
- STO, SIL 2 / PLd
- STO, SIL 3 / PLe
−default: Not required
```
+### The required integrity level comes from the machinery risk assessment for the driven equipment, and STO is now standard rather than optional on much of the drive market, so the field carries no default. {note}
+
## Electromagnetic Compatibility {toc}
### The drive installation shall meet the EMC immunity and emission requirements of IEC 61800-3 for the category appropriate to the installation environment.
−### The drive shall meet not less than IEC 61800-3 Category C2 emission limits, which is the minimum acceptable for most commercial and industrial installations.
+### The drive shall meet not less than the IEC 61800-3 emission category indicated in the datasheet.
```datasheet
…4 unchanged lines
- C2 (first environment, restricted)
- C3 (second environment, industrial)
+ - C4 (second environment, high power or IT network)
default: C2 (first environment, restricted)
```
+### C2 is the datasheet default because it is the practical minimum wherever the drive shares a service with commercial or institutional loads; C3 and C4 apply to dedicated industrial supplies where no sensitive equipment shares the source, and C1 to the rare drive on a residential service. {note}
+
# Source Quality Control {toc}
## Each drive shall be factory tested before shipment, including a functional power-on test of the control, protection, and communication features.
−## Drives furnished as factory-assembled combination packages — input reactor, output filter, and bypass in one enclosure — shall be assembled and wired at the factory and shipped as a tested unit. {note}
+## Drives furnished as factory-assembled combination packages — input reactor, output filter, and bypass in one enclosure — shall be assembled and wired at the factory and shipped as a tested unit.
# Installation {toc}
…5 unchanged lines
## Floor-mounted drive enclosures in applicable seismic design categories shall be anchored and braced in accordance with ASCE 7 and the project structural requirements.
−## Anchorage layout and conduit entry locations shall follow the arrangement shown on the drawings: [[drawing: VFD plan location and conduit entry]].
+## Drive locations shall be [[drawing: as indicated on the electrical plans]].
+## Conduit entry locations shall be [[drawing: as indicated on the approved shop drawings]].
+
## Input, output, and control conductors shall be terminated to the manufacturer's torque values, and shielded motor cable shall be terminated to maintain shield continuity.
−## On generator-backed projects, simultaneous starting of multiple drives shall be coordinated with the generator kVA rating so that drive inrush does not exceed the generator capacity; this is a frequent commissioning-discovered issue and shall be addressed in the sequence of operation. {note}
+## On generator-backed projects, simultaneous starting of multiple drives can exceed the generator kVA rating; this is a frequent commissioning-discovered issue. {note}
## The drive starting sequence on standby generator power shall be coordinated with the transfer and generator system so that connected drives start within the generator's capability.
# Testing {toc}
−## Field acceptance testing shall be performed in accordance with NETA ATS-2021 for adjustable-speed drives.
+## Field acceptance testing shall be performed in accordance with NETA ATS for adjustable-speed drives.
## Insulation resistance of the motor and motor circuit shall be measured and recorded before energizing the drive.
## Each drive shall be functionally verified for speed reference response, start and stop, fault and bypass operation, and network communication.
−## Where an IEEE 519-2022 compliance threshold is specified, harmonic current and voltage distortion shall be measured at the point of common coupling and recorded.
+## Where an IEEE 519 compliance threshold is specified, harmonic current and voltage distortion shall be measured at the point of common coupling and recorded.
## All adjusted parameters shall be recorded as as-left settings and submitted with the test report.
+## The field acceptance tests to be performed shall be as indicated in the datasheet.
+
```datasheet
label: Field acceptance tests required
…15 unchanged lines
# Identification {toc}
−## Each drive enclosure shall be provided with an engraved nameplate identifying the drive tag, the served motor, voltage, and horsepower.
+## Each drive enclosure shall be provided with an engraved nameplate carrying the content indicated in the datasheet.
−## Each drive shall bear a permanent warning label identifying the stored-energy hazard and the discharge time before the enclosure may be opened.
−
```datasheet
label: Nameplate engraving content
…10 unchanged lines
```
+## Each drive shall bear a permanent warning label identifying the stored-energy hazard and the discharge time before the enclosure may be opened.
+
# Delivery, Storage, and Handling {toc}
…2 unchanged lines
## Drives shall be stored indoors in a clean, dry, temperature-controlled space within the manufacturer's storage temperature range until installed.
−## Drives containing electrolytic DC-link capacitors that have been stored longer than the manufacturer's shelf limit shall be reformed in accordance with the manufacturer's instructions before energizing. {note}
+## Drives containing electrolytic DC-link capacitors that have been stored longer than the manufacturer's shelf limit shall be reformed in accordance with the manufacturer's instructions before energizing.
# Warranty {toc}
−## The manufacturer shall warrant each drive against defects in materials and workmanship for not less than the period specified below from the date of substantial completion.
+## The manufacturer shall warrant each drive against defects in materials and workmanship for not less than the period indicated in the datasheet, measured from the date of substantial completion.
```datasheet
label: Manufacturer warranty period
−type: radio
+type: range
unit: months
options:
− - "12"
− - "18"
− - "24"
− - "36"
− - "60"
−default: "24"
+ min: 12
+ max: 60
+ setpoints: [12, 18, 24, 36, 60]
+default: 24
```
# Spare Parts {toc}
−## The Contractor shall furnish the spare parts listed below, packaged and labeled for the served drives.
+## The Contractor shall furnish the spare parts indicated in the datasheet, packaged and labeled for the served drives:
- Spare control and cooling fans of each type used.
…12 unchanged lines
- Input fuses (each rating)
```