Trane Starters, Electrical Components, Drives, CVHE, CVHF Engineering Bulletin

...

Engineering Bulletin

Starters, Drives, and Electrical Components for CenTraVac™ Chillers

Models: CVHE, CVHF, CVHG, CDHF, CDHG

Only qualified personnel should install and service the equipment. The installation, starting up, and servicing of heating, ventilating, and air-conditioning equipment can be hazardous and requires specific knowledge and training. Improperly installed, adjusted or altered equipment by an unqualified person could result in death or serious injury.When working on the equipment, observe all precautions in the literature and on the tags, stickers, and labels that are attached to the equipment.

December 2011 CTV-PRB004-EN

SAFETY WARNING

Warnings, Cautions and Notices

Warnings, Cautions and Notices. Note that warnings, cautions and notices appear at

appropriate intervals throughout this manual.Warnings are provided to alert installing contractors to potential hazards that could result in death or personal injury. Cautions are designed to alert personnel to hazardous situations that could result in personal injury, while notices indicate a situation that could result in equipment or property-damage-only accidents.

Your personal safety and the proper operation of this machine depend upon the strict observance

of these precautions.

Read this manual thoroughly before operating or servicing this unit.

ATTENTION: Warnings, Cautions and Notices appear at appropriate sections throughout this

literature. Read these carefully:

WARNING

CAUTIONs

NOTICE:

Indicates a potentially hazardous situation which, if not avoided, could result in death or serious injury.

Indicates a potentially hazardous situation which, if not avoided, could result in minor or moderate injury. It could also be used to alert against unsafe practices.

Indicates a situation that could result in equipment or property-damage only accidents.

Important Environmental Concerns!

Scientific research has shown that certain man-made chemicals can affect the earth’s naturally occurring stratospheric ozone layer when released to the atmosphere. In particular, several of the identified chemicals that may affect the ozone layer are refrigerants that contain Chlorine, Fluorine and Carbon (CFCs) and those containing Hydrogen, Chlorine, Fluorine and Carbon (HCFCs). Not all refrigerants containing these compounds have the same potential impact to the environment.

Trane advocates the responsible handling of all refrigerants-including industry replacements for

CFCs such as HCFCs and HFCs.

Responsible Refrigerant Practices!

Trane believes that responsible refrigerant practices are important to the environment, our

customers, and the air conditioning industry. All technicians who handle refrigerants must be certified.The Federal Clean Air Act (Section 608) sets forth the requirements for handling, reclaiming, recovering and recycling of certain refrigerants and the equipment that is used in these service procedures. In addition, some states or municipalities may have additional requirements that must also be adhered to for responsible management of refrigerants. Know the applicable laws and follow them.

Proper Field Wiring and Grounding Required!

All field wiring MUST be performed by qualified personnel. Improperly installed and grounded

field wiring poses FIRE and ELECTROCUTION hazards. To avoid these hazards, you MUST follow requirements for field wiring installation and grounding as described in NEC and your local/state electrical codes. Failure to follow code could result in death or serious injury.

WARNING

Warnings, Cautions and Notices

WARNING

Personal Protective Equipment (PPE) Required!

Installing/servicing this unit could result in exposure to electrical, mechanical and chemical hazards.

• Before installing/servicing this unit, technicians MUST put on all Personal Protective Equipment (PPE) recommended for the work being undertaken. ALWAYS refer to appropriate MSDS sheets and OSHA guidelines for proper PPE.

• When working with or around hazardous chemicals, ALWAYS refer to the appropriate MSDS sheets and OSHA guidelines for information on allowable personal exposure levels, proper respiratory protection and handling recommendations.

• If there is a risk of arc or flash, technicians MUST put on all Personal Protective Equipment (PPE) in accordance with NFPA 70E or other country-specific requirements for arc flash protection, PRIOR to servicing the unit.

Failure to follow recommendations could result in death or serious injury.

Trademarks

Adaptive Frequency, CenTraVac, Duplex,TOPSS,Tracer AdaptiView,Tracer Summit,Trane, and the

Trane logo are trademarks or registered trademarks ofTrane in the United States and other

countries.Trane is a business of Ingersoll Rand. All trademarks referenced in this document are the trademarks of their respective owners.

Cutler-Hammer is a registered trademark of Eaton Corporation.

CTV-PRB004-EN 3

Table of Contents

Introduction ............................................................ 6

About Starters .......................................................... 7

What a Starter Does ................................................ 7

Motor Types and Voltage Classes ........................................ 8

Voltage Classes .................................................... 8

Motors ........................................................... 8

Chiller Selection and Electrical Specification ............................. 10

Standard Components of Trane Starters ............................. 10

Chiller Selection Report ............................................ 10

Motor Protection ...................................................... 13

Low-Voltage Starter Types ............................................. 17

Low Voltage—Wye-Delta ........................................... 18

Low Voltage—Solid-State .......................................... 22

Low Voltage—Unit-Mounted Adaptive Frequency Drive ................ 25

Low Voltage—Remote-Mounted Adaptive Frequency Drive ............. 28

Wye-Delta Starters ........................................... 18

Solid-State Starters ........................................... 22

Medium-Voltage Starter Types (2,300–6,600 Volts) ....................... 31

Medium Voltage—Across-the-Line (2.3–6.6 kV) .......................32

Across-the-Line Starter (2,300–6,600 volts) ........................ 32

Medium Voltage—Primary Reactor (2.3–6.6 kV) ....................... 35

Primary Reactor Starter (2,300–6,600 volts) ....................... 35

Medium Voltage—Autotransformer (2.3–6.6 kV) ...................... 38

Autotransformer Starter (2,300–6,600 volts) .......................38

Unit-Mounted Starter Top Hat—NEC 2005 Code Requirement ........ 40

Medium Voltage—Remote-Mounted Adaptive Frequency Drive ......... 42

Chiller Unit Control Features for the AFD ......................... 43

Medium-Voltage Starter Types (10,000–13,800 Volts) .....................45

Medium Voltage—Across-the-Line (10–13.8 kV) ....................... 45

Across-the-Line Starter (10,000–13,800 volts) ...................... 45

Medium Voltage—Primary Reactor (10–13.8 kV) ...................... 47

Primary Reactor Starter (10,000–13,800 volts) ..................... 47

Medium Voltage—Autotransformer (10–13.8 kV) ...................... 48

Autotransformer Starter (10,000–13,800 volts) .....................48

Electrical System—Ratings ............................................. 49

Electrical System—Design Guidelines ................................... 52

4 CTV-PRB004-EN

Disconnect Means ............................................ 52

Short-Circuit Interruption ...................................... 53

Power Circuit Requirements ....................................54

Electrical System–Power Wire Sizing .................................... 56

Starter Options ........................................................ 61

Multiple Starter Lineups (2,300–6,600 volts) ....................... 61

Industrial-Grade Starters ...................................... 63

Glossary .............................................................. 73

CTV-PRB004-EN 5

Introduction

This document explains key electrical concepts and starter product information relating toTrane

water chillers.Topics include voltage classes, motors, motor protection, starter types, variablefrequency drives, wire sizing, power factor correction, and electrical term definitions.

Information in this document changes frequently.To make sure you are viewing the most recent version, be sure to download the latest copy available on e-Library.

Dimensional data

Job specific submittals are always the best source of dimensional data. General starter dimensions are shown with the descriptions of each starter type in this document.

Wiring information

The best source for additional information is the Installation, Operation, and Maintenance manual

shipped with the chiller. Field connection diagrams are also available on the website.

All unit-mounted starters are designed for top-entry line power only. Remote starters are typically designed for top-entry line power and a bottom exit for load wires.The medium-voltage starter submittals show conduit space for alternate wiring options. Additional wiring options may be available.

For your convenience, power wire sizing charts for various voltages and conduit combinations are provided.

Fuse and circuit breaker sizing

Proper sizing of fuses and circuit breakers upstream of the starter is the responsibility of the customer or the electrical engineer. Disconnects and circuit breakers are options that can be installed within theTrane or local code requirements for installation of overcurrent devices.

Important: Trane, in presenting electrical information and system design and application

concepts, assumes no responsibility for the performance or desirability of any resulting system design. Design of the HVAC and related electrical system is the prerogative and responsibility of the engineering professional.Trane has a policy of continuous product and product information improvement and reserves the right to changedesign and specifications without notice. Consult the chiller submittal for the most up-to-date information as applied to the specific chiller under consideration.

starters. WhatTrane would install may not necessarily satisfy UL, NEC,

6 CTV-PRB004-EN

About Starters

What a Starter Does

Electric, centrifugal, water-cooled chillers use relatively large induction motors to drive the compressors.These motors use a control device to connect to and disconnect from the electrical power source.These control devices are referred to as combination controllers or, most commonly, as motor starters. Variable-frequency drives or Adaptive Frequency™ Drives (AFDs) also serve as motor starters, but their capabilities extend beyond starting and stopping the motor.

There are three main functions of the motor starter.The first function is to serve as the link between

the chiller’s motor and the electrical distribution system. It is used during the starting and stopping sequence.

Starting an induction motor from standstill causes a large electrical current draw for a few seconds.

The extra current is used to develop the required torque to get the compressor motor running at

full speed.The initial rush of current decreases as the compressor motor ramps up to full speed, and is commonly referred to as inrush current.

The second function of the starter is to keep the initial current inrush below a specified level.Third,

the starter communicates with the unit controller to coordinate motor protection.

Starters can be as simple or as complex as necessary to meet various engineering specifications and/or customer needs. A variable-speed drive can provide starter functions, among other things (see “Low Voltage—Unit-Mounted Adaptive Frequency Drive,” p. 25 and “Medium Voltage—

Remote-Mounted Adaptive Frequency Drive,” p. 42). It will be classified as a starter type for the

purposes of this document.

Several voltage classes and starter types are available as indicated on the chart below. Each one is described in greater detail in this document.

Table 1. Trane CenTraVac chiller starter choices

Low Voltage (208–600 V) Medium Voltage (2,300–6,600 V)

Remote-Mounted Unit-Mounted Remote-Mounted Unit-Mounted Remote-Mounted

Wye-Delta

Up to 1,700 amps

Solid-State

(Up to 1,120 amps with disconnect or circuit breaker required)

Adaptive Frequency Drive

460/480/575/600 V Up to 1,360 amps (460/480 V) 1,120 amps (575/600 V)

Wye-Delta

Up to 1,316 amps (Up to 1,120 amps with disconnect/circuit breaker option)

Solid-State

(Up to 1,120 amps with disconnect or circuit breaker required)

Adaptive Frequency Drive

Up to 1,210 amps Circuit breaker standard 460–480 V

Across-the-Line

Up to 360 amps Isolation switch, power fuses standard

Primary Reactor

Up to 360 amps Isolation switch, power fuses standard

Autotransformer

Up to 360 amps Isolation switch, power fuses standard

Adaptive Frequency Drive

Up to 250 amps Isolation switch, power fuses standard

Across-the-Line

Up to 288 amps Isolation switch, power fuses standard

Primary Reactor

Up to 205 amps Isolation switch, power fuses standard

Autotransformer

Up to 205 amps Isolation switch, power fuses standard

Medium Voltage

(10–13.8 kV)

Across-the-Line

Up to 94 amps Isolation switch, power fuses standard

Primary Reactor

Up to 94 amps Isolation switch, power fuses standard

Autotransformer

Up to 94 amps Isolation switch, power fuses standard

CTV-PRB004-EN 7

MotorTypes and Voltage Classes

Voltage Classes

There are two primary voltage classes typically used in the water-cooled chiller industry: low and

medium. For centrifugal chillers this is generally restricted to three-phase power only.

Low voltage ranges from 208 to 600 volts. Starters and frequency drives in this voltage range include sizes up to 1,700 amps.

Medium voltage has two main voltage groups. One ranging from 2,300 to 6,600 volts and the other ranging from 10,000 to 13,800 volts. Starters in this class have sizes up to 360 amps and 94 amps respectively.

For a given power (kW), the higher the voltage the lower the amperage.The voltage is typically established prior to creating the job plans and specifications.

Motors

A centrifugal motor is a relatively simple motor. Specifically, it is referred to as a three-phase, squirrel-cage, 3,600-rpm, alternating-current induction motor with two-pole construction.

The squirrel-cage motor consists of a fixed frame, or stator, carrying the stator windings and a

rotating member called the rotor. Figure 1 shows a cutaway of a typical low-voltage motor.The rotor is built by rigidly mounting steel laminations to the motor shaft.The motor winding consists of aluminum bars that are die-cast into slots in the rotor.The aluminum bars are connected at each end by a continuous ring.This skeleton of rotor bars with end rings looks like a squirrel cage and gives the motor its name.

Figure 1. Low-voltage motor Figure 2. Medium-voltage motor

Stator

Squirrel-cage

Rotor shaft

Stator

In a three-phase motor, three windings on the stator connect to a motor terminal board, and ultimately to the power grid via the starter.When the polyphase alternating current flows through the stator winding it produces a rotating magnetic field.The resulting magnetic forces exerted on the rotor bars cause the rotor to spin in the direction of the stator field.The motor accelerates until a speed is reached corresponding to the slip necessary to overcome windage and friction losses.

This speed is referred to as the no-load speed.

Low-voltage motors typically have six motor terminals to electrically connect the motor in a wye (star) or delta configuration. Most low-voltage motors are random-wound motors, but larger amperage higher horsepower motors are form wound for better heat dissipation. Connecting links can be used to convert the six motor electrical connections to three connections.

Medium-voltage motors (2,300–6,600 V) have three motor terminals. Figure 2 shows a typical medium-voltage motor minus the rotor shaft.You can visually compare most low- and medium-

8 CTV-PRB004-EN

MotorTypes and Voltage Classes

voltage motors. Medium-voltage motors are always form wound and you can see that the insulation is thicker and the windings are more evenly spaced.

Figure 3. Ceramic insulators on medium-voltage motor (10-13.8 kV)

Medium-voltage motors (10–13.8 kV) have the same design and construction attributes as other medium-voltage motors with some externally visible differences. Ceramic insulators and larger spacing of the motor terminals are commonly found on typical 10–13. kV medium-voltage motors. Internally, these motors are form wound and structurally similar to other medium-voltage motors.

The ceramic insulators combined with the larger spacing between the motor terminals help

prevent electrical arcing.

Higher voltage motors and starters are being used in large chiller plants where incoming line power makes 10–13.8 kV accessible. In some cases, higher voltage chillers allow for the elimination of electrical components with their associated space requirements and energy losses. In particular, chiller installations with on-site or dedicated power generation, such as district cooling, higher education, hospitals, industrials, and airports have opportunities for electrical distribution system simplification and energy savings.

Benefits of 10,000–13,800 volts include:

• No need for step-down transformer

• No transformer losses

• Higher uncorrected power factor

• Reduced electrical design and labor

• Reduced mechanical room space

Note: Motors and starters at 10,000–13,800 volts typically cost more, and the motor efficiency is

lower than 2,300–6,600-volt motors.

Motors are available in specific power sizes, which are rated in kilowatts or horsepower.The

TOPSS™ computer software selection program selects the proper motor to meet the specific

cooling duty of the application.

CTV-PRB004-EN 9

Chiller Selection and Electrical Specification

Standard Components of Trane Starters

• A 4 kVA control-power transformer (CPT) supports all of the chiller auxiliary power needs— 3 kVA control-power transformer supplied with AFDs.

• Primary and secondary current transformers (CTs) support the overload and momentary power loss protection functions of the unit controller.This allows amps per phase and percent amps to be displayed at the unit controller.

• Potential transformers (PTs) support motor protection functions such as under/overvoltage within the unit controller.This allows voltage per phase, kilowatts, and power factor to be displayed at the unit controller.

• Grounding provisions are standard.

• A terminal block for line power connection is standard. Load-side lugs are standard for remote starters.The lug sizes and configuration are shown on the submittal drawing.TheTrane has a circuit breaker as standard. Medium-voltage starters have provisions for a bolted connection.

Chiller Selection Report

The following terms are found on a typicalTOPSS product report. Review the example selection

output report shown in Figure 4, p. 12.

Electrical information

Usually the primary RLA (incoming line), compressor motor RLA, and kW of the chiller are used as nameplate values. In this section, we will review the typical electrical data presented on the selection report.

AFD

A. Motor size (kW). The motor size is listed on the program report based on its output kW.The

output kW is the motor’s full, rated power capacity.There is an amperage draw associated with the motor size called full-load amps (FLA). FLA is the amperage the motor would draw if it were loaded to its full rated capacity, i.e. the motor size. The FLA is not available from the chiller selection program, but it can be obtained from motor data sheets upon request.

B. Primary power (kW). The primary power is the power the chiller uses at its design cooling

capacity.The primary power will always be less than or equal to the motor size.

C. Motor locked-rotor amps (LRA). There is a specific locked-rotor amperage value associated

with each specific motor.This is the current draw that would occur if the rotor shaft were instantaneously held stationary within a running motor. LRA is typically six to eight times the motor full-load amps (FLA). LRA is also used commonly in discussing different starter types and the inrush amperages associated with the motor start. For example, a wye-delta starter will typically draw approximately 33 percent of the motor LRA to start. A solid-state starter will draw approximately 45 percent of the motor LRA to start.

D. Primary rated-load amps (RLA [incoming line]). The RLA is also commonly referred to as

the selection RLA or unit RLA.This is the amperage that is drawn on the line side when the chiller is at full cooling capacity. Nameplate RLA (usually the same as primary RLA [incoming line]) is the key number used to size the starter, disconnects, and circuit breaker. Primary RLA (incoming line) is also the value used to determine the minimum circuit ampacity (MCA) for sizing conductors. Primary RLA (incoming line) is always less than or equal to the motor full-load amps (FLA).

E. Compressor motor RLA. This is the amperage between the motor and starter or AFD. If the

unit is a starter, the compressor motor RLA will be almost identical to the primary RLA (incoming line). If the unit is an AFD, typically, the compressor motor RLA will be larger.This value is used to size the AFD.The primary RLA (incoming line) is lower due to the improved power factor of the AFD.

10 CTV-PRB004-EN

Chiller Selection and Electrical Specification

F. Minimum circuit ampacity (MCA). This term appears on the chiller nameplate and is used

by the electrical engineer to determine the size and number of conductors needed to bring power to the starter.

MCA = 1.25 x (Primary RLA [incoming line])+

… with this number rounded up to the next whole number. Said another way, the MCA is 125 percent of the motor design primary RLA (incoming line) plus 100 percent of the amperage of other loads (sump heater, oil pump, purge, etc.).The MCA is listed on the chiller selection report. Power cable sizes and conduits are discussed in “Electrical System–PowerWire Sizing,” p. 56. If the AFD is a remote, free-standing AFD, the MCA will be based on the compressor motor RLA.

(

4000

volts

motor

)

G. Maximum overcurrent protection (MOP or MOCP). The MOP appears on the chiller

nameplate.The electrical engineer often wants to know the MOP when the chiller is selected for sizing fuses and upstream circuit breakers. Understand that the MOP is a maximum, NOT a recommended fuse size. Improperly sized circuit breakers or fuses can result in nuisance trips during the starting of the chiller or insufficient electrical protection. MOP is also NOT used to size incoming power wiring—the MCA is used for this purpose.

CTV-PRB004-EN 11

Chiller Selection and Electrical Specification

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12 CTV-PRB004-EN

Motor Protection

Historically, motor protection was provided in the starter by some type of monitoring system. Starter manufacturers usually provide a full range of optional equipment mounted on the starter. Eaton Cutler-Hammer

Today,Trane provides most of the key motor protection and metering functions (see Table 2, first

column) within the chiller microprocessor control panel as standard. Having the motor control and chiller control in one panel provides better integration and optimization of the two control systems. For example, the chiller controller can unload the chiller when approaching an overload “trip” point, so that the chiller stays online.

Table 2 and Table 3, p. 14 can be used to compare the standard electrical features of the chiller

controller with those of other common Eaton Cutler-Hammer Additional starter-mounted metering and motor protection may not be required and could be considered redundant.These devices are not available for AFDs.

Table 2. Protection and functions by motor packages

offers IQ metering and motor protection products for their starters.

starter-only-mounted devices.

Protection Functions

Communications Optional Optional Optional Optional Ground fault Optional Long acceleration Standard Standard N/A N/A Maximum number of starts Standard Standard N/A N/A Momentary power loss (distribution fault) Standard N/A N/A N/A Motor overload Standard Standard N/A N/A Motor winding temperature Standard Over temperature Standard N/A N/A N/A Overvoltage Standard Phase imbalance Standard Standard N/A Standard Phase loss Standard Standard N/A Standard Phase reversal Standard N/A N/A Standard Run timer Standard Standard N/A N/A Separate alarm levels Surge capacitor/lightning arrestor Optional N/A N/A N/A Undervoltage Standard

(a)The MP 3000 features Intel-I-Trip overload protection, enhanced custom trip curve development, UL 1053 ground fault, and advanced data logging and

diagnostics. (b)For low voltage, a Trane-supplied circuit breaker or non-fused disconnect is also required when ground fault is specified. (c) The chiller controller monitors the motor temperatures of all three phases with one resistance temperature detector (RTD) per phase (d)For this option, add one or two sets (three RTDs per set) of 100-ohm platinum RTDs to the motor. Contact La Crosse Field Sales Support. (e) Under/over phase-voltage sensors include volts per phase, kW, power factor, kWh, and under/overvoltage. A required pick on medium-voltage starters. (f) Three alarm levels are used: warning only, nonlatching (auto-reset), and latching (manual reset required).

(f)

Tracer AdaptiView MP 3000

(b)

(c)

(e)

Standard Standard N/A N/A

(e)

Standard N/A N/A

Optional

N/A N/A Standard

(d)

(a)

IQ 150 IQ DP 4130

N/A N/A

CTV-PRB004-EN 13

Motor Protection

Table 3. Starter ONLY: metering functions and accuracies

Metering Functions Tracer AdaptiView MP 3000

Ampere demand N/A N/A Standard (±0.25%) Standard (±0.3%) Current (%RLA) Standard (±3% to ±7%) Standard N/A N/A Current (3-phase) Standard (±3%) Standard Standard (±0.25%) Standard (±0.3%) Voltage (3-phase) Standard Frequency N/A N/A Standard Standard Harmonic distortion current N/A N/A N/A Standard (31 Harmonic distortion voltage N/A N/A N/A Standard (31 Kilowatt Standard Power factor Standard VA (volt-amperes) N/A N/A Standard (±0.5%) Standard (±0.6%) VA demand N/A N/A Standard (±0.5%) Standard (±0.6%) VA hours N/A N/A Standard (±0.5%) Standard VARs (volt-amperes reactive) N/A N/A Standard (±0.5%) Standard (±0.6%) VAR demand N/A N/A Standard (±0.5%) Standard (±0.6%) VAR-hours N/A N/A Standard (±0.5%) Standard Watt, see Kilowatt Standard Watt demand Standard N/A Standard (±0.5%) Standard (±0.6%) Watt-hours Standard N/A Standard (±0.5%) Standard

(a)The MP 3000 features Intel-I-Trip overload protection, enhanced custom trip curve development, UL 1053 ground fault, and advanced data logging and

diagnostics. (b)Under/over phase-voltage sensors include volts per phase, kW, power factor, kWh, and under/overvoltage. A required pick on medium-voltage starters.

(b)

(±2%) N/A Standard (±0.25%) Standard (±0.3%)

(b)

(±5%) N/A N/A N/A

(b)

(±5%) N/A Standard Standard

(b)

N/A Standard (±0.5%) Standard (±0.6%)

(a)

IQ 150 IQ DP 4130

)

Overload protection

Overload or overcurrent protection shields the motor from small levels of overcurrent ranging from 107 to 140 percent of the primary RLA of the chiller. In contrast, fuses and circuit breakers are used to protect against short-circuit currents which may range to well over 100,000 amps.

Inductive loads, such as a chiller motor, behave differently than resistive loads such as electric heaters.Their current draw is greatest at startup and corresponds to the existing load when running. In other words, a motor operating normally draws rated amps (RLA) at rated load, fewer amps at less-than-rated load and more amps at greater-than-rated load. It is the latter condition that requires overload protection.

Adding an overload protection device prevents the motor from drawing more than its rated amperage for an extended period. Basic overload devices simply open the circuit when current draw reaches the “trip” point. More sophisticated devices attempt to restore normal motor operating conditions by reducing the load, but will disconnect the motor if overloading persists.

As with most overload devices, the chiller controller determines the “trip time” by measuring the magnitude of the overload. It then compares the overload to the programmed RLA “time-to-trip” curve. At startup, the standard overload protection is bypassed for the starter’s acceleration time, or until the motor is up to speed. Refer to Figure 5, p. 15 for the chiller controller’s overload timeto-trip curve.

14 CTV-PRB004-EN

Figure 5. Tracer AdaptiView chiller controller overload time-to-trip curves

Overload Trip

Time (sec)

Motor Protection

Nominal

Minimum

Maximum

108

102

Overload situations, left unchecked by protection, can cause excessive motor heat, that can permanently damage the windings and lead to motor failure.The time until motor damage depends mainly on the magnitude of the overcurrent and has an inverse time versus current relationship.The greater the overcurrent, the less time it takes to cause motor damage.

Overcurrent can be the result of motor overload, low line voltage, unbalanced line voltage, blocked load (rotor cannot freely rotate), single phasing, bad connections, broken leads, or other causes. It can occur in any one winding, a set of windings, or in all the motor windings.

The threshold of overcurrent is generally the primary RLA, which may be raised for service factor

or lowered due to any derating factor, such as ambient temperature or line-voltage imbalance.

Overload protection is bypassed during a start due to the high currents associated with locked rotor and motor acceleration. Maximum allowed acceleration times per the AdaptiView unit controller are listed in Table 4.

Table 4. Long acceleration protection

Starting Method (starter type)

Wye-Delta 27 Solid-State 27 Variable-Frequency Drive 12 Across-the-Line 6 Primary Reactor 16 Autotransformer 16

Maximum Setting for the Acceleration Timer (sec)

114

120

126

132

% Run-Load Amps

138

144

150

Motor overheat protection

The unit controller monitors the motor winding temperatures in each phase and terminates chiller

operation when the temperature is excessive.This feature also prevents the chiller from starting if the motor temperature is too high.

Momentary power loss protection (distribution fault)

Momentary power losses longer than two or three line cycles will be detected and cause the chiller to shut down, typically within six cycles. The chiller can also shut down due to excessive or rapid voltage sags. Shutting down the chiller prevents power from being reapplied with different motor phasing.

CTV-PRB004-EN 15

Motor Protection

Phase failure/loss protection

The chiller will shut down if any of the three-phases of current feeding the motor drop below

10 percent RLA for 2.5 seconds.

Phase imbalance protection

Based on an average of the three phases of current, the ultimate phase-imbalance trip point is 30 percent.The RLA of the motor can be derated depending on the percent of this imbalance.The phase-imbalance trip point varies based on the motor load.

Phase reversal protection

Detects reverse-phase rotation and shuts the chiller down (backwards rotation).

Under/overvoltage protection

The chiller is shut down with an automatic reset due to excessive line voltage ±10 percent of the

design voltage.

Short cycling protection

Prevents excessive wear on the motor and starter due to heating from successive starts.The unit controller uses an algorithm based on a motor heating constant and a background timer (measuring the running time since the last start).

Supplemental motor protection

This is a set of optional motor protection features, offered as a option in addition to the Enhanced

Electrical Protection Package (see “SMP, Supplemental Motor Protection—Medium voltage only

(Enhanced Electrical Protection Package option),” p. 66).

16 CTV-PRB004-EN

Low-Voltage StarterTypes

Table 5 shows the most common low-voltage starter types available and lists their advantages and

disadvantages.Typical inrush acceleration profiles for these starters are shown in Figure 6, p. 18. It is very uncommon to see a full-voltage starter in a low-voltage application due to the high inrush current; however, it is represented on the chart to provide a frame of reference.

Which starter type is best?

The wye-delta starter has been around a long time and, except for an AFD, it draws the lowest

inrush current.Wye-delta starters are electromechanical and service technicians are typically more comfortable with them.The solid-state starter is a relatively newer design compared to the wyedelta, and has a slightly higher inrush current in chiller applications.The solid-state starter inrush can be set lower (the starter takes longer to get the motor up to speed), but it must be above the minimum inrush required to develop the proper starting torque.The solid-state starter is comparable in price to the wye-delta starter and has a smoother inrush curve without any current spikes.The wye-delta’s transition spike is not long enough to set utility demand ratchets or reduce the life of the motor.The starter type chosen ultimately depends on the application.

Table 5. Comparison of low-voltage starter types

Starter Type (closed-transition

Wye-Delta (Star-Delta)

Solid-State ~45 33 15%

Adaptive Frequency Drive (AFD)

Inrush Current % LRA

33 33 60%

<13 (<RLA)

Percent Rated Torque

varies 25%

How Often Used Advantages Disadvantages

Trane Adaptive Frequency Drives provide motor control, but they are much more than just starters. They also control the operating speed of the compressor-motor by regulating output voltage in

proportion to output frequency. Varying the speed of the compressor-motor can translate into significant energy savings.

Applications that favor the use of an AFD exhibit increased operating hours at reduced condenser water temperatures and high energy costs. However, it is important to recognize that all variablespeed drives, including theTraneAFD, require more energy near full-load design conditions, often coinciding with the peak electrical demand of the building.This may result in higher demand chargesand diminish the overall energy savings.An analysis of the full-year operation of the chiller plant using an hour-by-hour simulation program that does not use blended kW and kWh energy rates will help determine whether an AFD is appropriate for a specific application and location.

• Equal reduction of torque and inrush current

• Low cost

• Can be unit mounted

• Gradual inrush/ramp up

• No “spike” at transition

• Price comparable to the wyedelta

• Lowest inrush current

• Better chiller efficiency at reduced lift

• Only applicable up to 600 volts

• “Spike” at transition

• Higher level of service expertise than wye-delta

• Higher inrush current than wye-delta

• Starting harmonics may be an issue

• Most expensive

• Efficiency loss at full load

• Harmonics may be an issue

Typical Acceleration Time (seconds)

5–12

8–30

Unit or remote mounted?

Unit-mounted starters can save on installed cost and space, and they can be tested in the factory and shipped on the chiller in a NEMA 1 enclosure. Remote-mounted starters provide more options for multiple starter lineups, and may be chosen in order to implement some of the industrial starter options such as high-fault and NEMA 12/3R.

CTV-PRB004-EN 17

Low-Voltage StarterTypes

Figure 6. Comparison of low-voltage starting current

120

100

% LRA

Low Voltage—Wye-Delta

Wye-Delta Starters

One of the most common starters in the industry is the wye/star-delta. It is an electromechanical starter initially set up in a “wye” or “star” configuration, then it transitions to a “delta” configuration during the starting sequence.To illustrate a typical starting sequence using a generic (non-Trane) schematic, refer to Figure 7, p. 19 and its “Starting sequence,” p. 19.

X-Line

Solid-State

Wye-Delta

AFD

123456789

Time (seconds)

18 CTV-PRB004-EN

Figure 7. Simplified wye-delta wiring schematic

LINE

VOLTAGE

WYE-DELTA

STARTER WIRING

Low-Voltage StarterTypes

TRANSITION

MOTOR

CPT

START-

STOP

Starting sequence

1. The “start” signal from the CenTraVac controller energizes the pilot relay (PR).

2. The PR contacts close to energize the star contactor (S).

3. The S contacts close to connect the motor in the star configuration.

4. An S interlock closes to energize the start contactor (1M).

5. The 1M contacts close to connect the motor to the line.

6. A time delay relay or current monitoring device initiates transition by energizing the resistor contactor

. 1A contacts close to connect the resistors to the line in the star configuration and in parallel with

the compressor

8. A 1A interlock now opens to de-energize the S contactor.

9. The S contacts open to connect the resistors and motor windings in series in the delta configuration.

10. An S interlock closes to energize the run contactor (2M).

11. The 2M contacts close to bypass the resistors and connect the compressor motor directly to the line

(1A).

motor.

the delta configuration.

Dimensions

The typical unit-mounted wye-delta starter size is shown in Figure 9, p. 20. Typical remote-

mounted one-, two- and three-door starter sizes are shown in Figure 10, p. 20, Figure 11, p. 20, and

Figure 12, p. 21. Always consult the submittal drawings for as-built dimensions.

CTV-PRB004-EN 19

Low-Voltage StarterTypes

The one-door remote-mounted starter size is generally used for 155- to 606-amp starters with no

disconnect.The two-door size is used for 640- to 1,700-amp starters with no disconnect.The threedoor size is used for 1,385- to 1,700-amps when disconnects are included.

Figure 8. Unit-mounted WD Figure 9. Remote 1-door WD

Stator

Squirrel-cage

60”

84”

Rotor shaft

13.5”

38.5”

32”

Figure 10. Remote 2-door WD Figure 11. Remote 3-door WD

Stator

19.3”

Stator

Squirrel-cage

84”

Rotor shaft

Stator

84”

56”

20 CTV-PRB004-EN

19.3”

84”

Figure 12. Unit-mounted, wye-delta starter

Low-Voltage StarterTypes

1. Top-entry power only

2. 4 kVA control-power transformer

3. Circuit breaker (optional)

4. Transition resistors

Standard features

• Unit or floor mounted

• Control-power transformer

• Padlock tab for additional locking of the starter door

• Line-side connection terminal block/main lug only

• UL and CUL certified

• Environmental specification

• Designed, developed, and tested in accordance with UL 508

• NEMA 1 enclosure as standard

• Operation from sea level to 6,000 ft (1,829 m)

• Operating ambient temperature range 32°F to 104°F (0°C to 40°C)

• Relative humidity, non-condensing 5 percent to 95 percent

• Non-operating ambient temperature range -40°F to 158°F (-40°C to 70°C)

• Voltage utilization range ±10 percent

CTV-PRB004-EN 21

Low-Voltage StarterTypes

Low Voltage—Solid-State

Solid-State Starters

TheTrane®solid-state starter produces a soft start with a gradual inrush current and no transition

spikes. It controls the starting characteristics of a motor by controlling the voltage to the motor. It does so through the use of silicon controlled rectifiers (SCRs), which are solid-state switching devices, and an integral bypass contactor for power control. An SCR will conduct current in one direction only when a control signal (gate signal) is applied. Because solid-state starters use alternating current (AC), two SCRs per phase are connected in parallel, opposing each other so that current may flow in both directions. For three-phase loads, a full six-SCR configuration is used, as shown in Figure 13.

Figure 13. Six-SCR arrangement

Starting sequence

During starting, control of current or acceleration time is achieved by gating the SCRs “on” at different times within the half-cycle.The gate pulses are originally applied late in the half-cycle and then gradually applied sooner in the half-cycle. If the gate pulse is applied late in the cycle, only a small increment of the wave form is passed through, and the output is low. If the gate pulse is applied sooner in the cycle, a greater increment of the wave form is passed through, and the output is increased. By controlling the SCRs ’ output voltage, the motor’s acceleration characteristic and current inrush are controlled as illustrated in Figure 14.

Figure 14. Starting sequence wave forms

25% voltage 50% voltage full voltage

When the SCRs are fully “phased on,” the integral bypass contactors are energized.The current

flow is transferred from the power pole to the contactors.This reduces the energy loss associated with the power pole, and extends contactor life.When the starter is given the stop command, the SCRs are gated “full voltage” and the bypass contactor is de-energized.The current flow is transferred from the contactors back to the power poles. Less than one second later, the SCRs are turned off and the current flow stops.

22 CTV-PRB004-EN

Low-Voltage StarterTypes

Features

• Unit- and floor-mounted models are available

• Control-power transformer

• Starting current is factory set and field adjustable

• Starting torque is factory set and adjustable via a voltage “notch” setting

• Six-SCR power section

• Air-cooled design with bypass contactor eliminates need for a water-cooling circuit, pump, and heat exchanger

• Bypass contactor rated to carry 100 percent of the full-load motor phase current

• Protection from shorted SCRs and high starter heatsink temperature

• Protection from transient voltage through resistor-capacitor (RC) snubbers across SCRs and metal oxide varistors (MOVs)

• Padlock tab for additional locking of starter door

• Line-side connection terminal block/main lug only

• UL and CUL certified

Dimensions

Typical dimensions for unit- or remote-mounted solid-state starters are shown in Figure 15. Always

consult the submittal drawings for as-built dimensions.

Figure 15. Solid-state dimensions

38.5"

60"

13.5"

CTV-PRB004-EN 23

Low-Voltage StarterTypes

Figure 16. Unit-mounted, solid-state starter

1. Top-entry line power

2. Intelligent technology (IT) controller

3. Starter control board

4. Potential transformers

5. 4 kVA control-power transformer

Environmental specification

• Designed, developed, and tested in accordance with UL 508

• NEMA 1 enclosure as standard

• Operation from sea level to 6,000 ft (1,829 m)

• Operating ambient temperature range 32°F to 104°F (0°C to 40°C)

• Relative humidity, non-condensing 5% to 95%

• Non-operating ambient temperature range -40°F to 158°F (-40°C to 70°C)

• Voltage utilization range ±10%

24 CTV-PRB004-EN

Low-Voltage StarterTypes

Low Voltage—Unit-Mounted Adaptive Frequency Drive

TheTrane Adaptive Frequency Drive is a refrigerant-cooled, microprocessor controlled design.The

AFD is used in lieu of a constant-speed starter and is currently available for use with 460 or 480 volts only. Adaptive Frequency is a trademarked term for theTrane proprietary control logic and made toTrane specifications.

About the Trane AFD

The AFD is unit-mounted and ships completely assembled, wired, and tested from the factory.The

AFD controller is designed to interface with the chiller controller. It adapts to the operating ranges and specific characteristics of the chiller.The optimum chiller efficiency is created by coordinating the compressor-motor speed with the compressor inlet guide vanes.The chiller controller and the AFD controller work together to maintain the chilled-water setpoint and avoid surge. If surge is detected, the chiller controller’s surge-avoidance logic in the chiller controller makes the proper adjustments to move the operating point away from surge.

How it works

The frequency drive regulates output voltage in proportion to output frequency to maintain ideal

motor flux and constant torque-producing capability.Or put simply, a variable-speed drive controls load-side frequency and voltage to adjust the compressor motor speed.The AFD is a voltagesource, pulse-width modulated (PWM) design. It consists of three primary power sections as shown in Figure 17: the active rectifier, the DC bus, and the inverter.

variable-speed drive, using

Figure 17. AFD power sections

Rectifier DC Bus Inverter

Determines line-side harmonics Determines load-side harmonics

Rectifier (active). Takes incoming AC power, filters it with an LCL filter (not shown), and then

converts it to a fixed DC voltage. The insulated-gate bipolar transistor (IGBT) active rectifier significantly reduces the amount of line-side harmonic levels and the amount of ripple on the DC bus.The active rectifier also has some traditional post-generation filtering capabilities to further smooth out remaining line-side harmonics.

DC bus. Capacitors store the DC power provided by the rectifier until it is needed by the inverter.

Inverter. Converts the DC voltage into a synthesized AC output voltage.This synthesized output

controls both the voltage and the frequency.The synthesized output waveform consists of a series of pulses, hence the “pulse” in PWM.

Starting sequence

Trane AFDs are programmed to start the compressor motor using low frequency and low voltage,

thereby minimizing the inrush current.The motor is then brought up to speed by gradually increasing both frequency and voltage at the same time.Thus, current and torque are much lower during startup and motor acceleration than the high current, high torque associated with acrossthe-line or even reduced-voltage starters; refer to the inrush current vs. time graph (Figure 6, p. 18).

CTV-PRB004-EN 25

+ 57 hidden pages

Trane Starters, Electrical Components, Drives, CVHE, CVHF Engineering Bulletin

Specifications and Main Features

Frequently Asked Questions

User Manual