IEEE-IAS 2012.02.18 Presentation - Motor Starting Techniques

IEEE - IASMotor Parameters &

Starting

By: James S. Nasby -- Columbia Engineering

Topics to be CoveredI. Induction Motors –

General

II. Electrical Power Supply

III. Induction Motor Parameters

IV. 3Ø Motor Starting Types (8+1)

V. 3Ø Motor Running Types (3)

VI. Common Motor Wiring Types (14)

VII. Installation Considerations

I. Motors – GeneralMotor Types

Induction Motors Three Phase Non-Salient Pole Motors:

Usually Squirrel Cage Rotor Motors -but- can be Wound Rotor (Slip Ring) Induction Motors

Design Type: NEMA Design “B”Normal Starting TorqueNormal Starting Current (KVA)

Synchronous, Single Phase & D.C. Motors Not Covered

I. Induction Motors General Definitions

Motor Poles – Even Numbers (2, 4, 6, etc.) Full Load Speed – Synchronous Speed - Slip Starting Region – Basically Fixed

Impedance Running Region – Energy Converter Torques:

Stall = Locked = Zero Speed Torque

Pull-up Torque

Breakdown Torque

Rated Torque Starting Amps, KVA & Locked Rotor Code Motor Housings TEFC & ODP

Motor Starting Region – cont’dMotor Torque Curve

Motor Torque and Pump Torque Curves

II. Electrical Power Supplies

Power Sources - Mains

Types of Power Source– Three Phase A.C.

Power Source Characteristics

(Parameters)– Voltage (Utilization Voltage) -at- – Low voltage or Medium Voltage– Frequency – 50 Hz or 60 Hz– Starting Voltage Drop -vs- Starter

– Running Voltage Drop -vs- Motor

Power Supply Characteristics – cont’d

- Power Quality - Source Capacity - Weak or Stiff Source

– Starting Voltage Drop (15% of Controller Rated)

– Running Voltage Drop (5% of Motor Rated)– Method of Calculating - NEMA ICS-14– Gen-Sets - Frequency & Voltage

Voltage Balance (Amount of Imbalance)- Small Voltage "Unbalance" = Large Current

Imbalance. See NEMA MG-1, part 14.35.- Typical 6% to 10% Current Imbalance for each

1% Voltage Imbalance per MG 1-14.35.5. - This is due to the motor trying to bring up the

low voltage leg (acting as a generator).

Voltage Harmonics (Heats Windings)

Power Factors - Affected by Motor

III. Induction Motor ParametersGeneral Motor Characteristics Induction Motor Types

– Wound Rotor Motor

(Slip Ring Motor)E.g.: Rotary Transformer

– Squirrel Cage Motor = Ditto– But with Slip Rings Shorted

Frequency – 50 Hz -vs- 60 Hz NEMA Design Type “B” (MG-1)

(Normal Starting Torque, Starting Current, Breakdown Torque, and Slip)

NEMA Design Types

Standard Three Phase

Induction Motors are

NEMA Design “B”

( Rated Full Load Torque)

Rated | Speed (RPM)

Induction Motors - cont’d Motor Parameters - Electrical

Locked Rotor Code (KVA per Hp) Service Factors

– Typically 1.15 Maximum Allowed– Often Higher for Smaller Motors– Usually 1.0 Max. when used with VFD's and often with TEFC motors.

Service Factor (S.F.) -vs- Ideal Conditions– Max. Temperature (40 °C Max.) -and-– Max. Altitude (3,300 ft /1,000 m Max.) -and-

– Max. Voltage Imbalance (1% Max.)

Motor Parameters – cont’d Abbreviations & Acronyms Motor Currents

– FLA = Motor Full Load Amperes– FLC = Motor Full Load Current = FLA– LRC = LRA = Locked Rotor Current (Amps)– SFA = Service Factor Amps – Locked Rotor Code* – Codes F & G

Common

*May be Much Higher for Smaller Motors and for Energy Efficient Motors

Power Factor (PF) – Real -vs- ImaginaryStarting PF = 30% / 40% TypicallyRunning PF = 85% down to 8.0% from Full Load to No Load, Typically

Motor Parameters – cont’d Motor Current Curve

Motor Current -vs- RPM Curves

Rated Running Current = 100%

Induction MotorLocked Rotor Codes

Maximum Allowed Motor Locked Rotor Codes per NFPA-20:

Code "F" for 15 Hp & up -or-5.0 thru 5.59 KVA/Hp = approx. 540% FLA

Code "G" for for 15 Hp & up5.6 thru 6.3 KVA/Hp = approx. 600% FLA

Code "H" for 5 thru 10 Hp(up to 7.1 KVA/Hp = approx. 685% of FLA)

Code "J" for 5 Hp only(up to 8.0 KVA/Hp = approx. 772% of FLA)

Induction Motor Locked Rotor Codes

Table M-02 -- Motor Locked Rotor Code KVA Data and Allowed Horsepowers

"F" "G" "H" "J" Code Letter

Min. Max. Min. Max. Min. Max. Min. Max.

KVA per Hp 5.00 5.59 5.60 6.29 6.30 7.09 7.10 7.99 LRA/FLA 482% 540% 540% 608% 608% 685% 685% 772% Allowed Hp 15 Hp and up 15 Hp and up 5 thru 10 Hp 5 Hp only

Note: The LRA/FLA ratios shown are approximate for illustration only.

Table M-03 -- Maximum Motor Locked Rotor Currents

Motor Voltage - 60 Hz values Rated

Horsepower

Code

Letters 200 Vac 208 Vac 230 Vac 460 Vac 575 Vac

5 F - J 106 102 92 46 37 7.5 F - H 147 142 128 64 51 10 F - H 186 179 162 81 65 15 F - G 267 257 232 116 93 20 F - G 334 321 290 145 116 25 F - G 421 405 366 183 146 30 F - G 499 480 434 217 174 40 F - G 667 641 580 290 232 50 F - G 833 801 724 362 290 60 F - G 1,001 962 870 435 348 75 F - G 1,249 1,201 1,086 543 434 100 F - G 1,668 1,603 1,450 725 580 125 F - G 2,088 2,008 1,816 908 726 150 F - G 2,496 2,400 2,170 1,085 868 200 F - G 3,335 3,207 2,900 1,450 1,160 250 F - G 4,198 4,036 3,650 1,825 1,460 300 F - G 5,060 4,865 4,400 2,200 1,760 350 F - G 5,865 5,639 5,100 2,550 2,040 400 F - G 6,670 6,413 5,800 2,900 2,320 450 F - G 7,475 7,188 6,500 3,250 2,600 500 F - G 8,338 8,017 7,250 3,625 2,900

Note: The 460 Vac LRA values are from NFPA 20 Table 6-5.1.1. Others are calculated using voltage proportion.

Induction Motor Locked Rotor Currents

Motor Parameters – cont’d Motor Stalled (Locked Rotor) Power Factor = Approx 40%

Motor Parameters – cont’d Motor Theory and Formulae

Purpose – Electrical to Mechanical Energy Conversion

– Motor Starting Region (Rotary Solenoid)– Running Region (Energy Converter)

Motor Torque & Motor Current Draw -vs- Speed Curves A‑T‑L‑Starting

(Basic Motor Characteristics)– Power Factor & Phase Angles– Efficiencies

Motor Starting -vs- Motor Running Regions

Motor Starting -vs- Motor Running Regions

Motoring Region

Starting Region

Motor Parameters – cont’d Motor Torque Curve

Motor Torque and Pump Torque Curves


Motor Current -vs- RPM Curves



Motor Current -vs- RPM CurvesNote where 115% S.F. is on vertical axis.


Motoring RegionStarting Region

100% (FLA)

Motor Theory and Formulae

Motor Starting RegionFor a Motor at Stall, Motor Impedance

is Constant. So: I = E / Z (Ohm’s Law)

Current is Directly Proportional to Motor Voltage. I.E.:

Motor Current = Voltage / Impedance

Power Factor (P.F.) is Typically 30% to 40% at Stall and for most of the starting region. Important for starting voltage drop (115%) calculations.

Motor Theory and Formulae

Motor Starting Region – cont’d

In the Starting (Accelerating) Region:Torque is Proportional to the Square

of the Applied Motor Voltage T = K1 x V2 -or- Since Current is proportional to Voltage (see above): T = K2 x I2

Thus: Torque is also Proportional to the Square of the Motor Current Relevant for reduced starting torques

Motor Theory and FormulaeMotor Starting Region – cont’d

Example of Starting Torque Proportional to the Square of Applied Motor Voltage.

E.G. 50% Volts = 25% of Rated Stall Torque.

Motor Theory and Formulae Motor Running Region

Motor Running Region (Energy Converter):Mechanical Power is Torque x Speed:

Pm = K3 x Tq x RPMMotor Torque is Whatever the Load

RequiresElectrical Power Input is:

Pe = Pm + Motor Losses = Pm / EfficiencyBut, Electrical Power Input is also given as:

Pe = K4 x V x Ireal (Volts x Real Current)So: Ireal = K5 x Pe / VoltsThus Motor Current is Inversely Proportional

to Motor Voltage with a Running Motor

Motor Running -vs- Motor Starting Regions

Rated Torque (100%) times Rated Speed (E.g. 1750 RPM) yields Motor Rated Horsepower.

IV. Motor Starting General ‑ Overview – Types of

Reduction– Voltage Reduction: Wye–Delta, Soft Start,

and Autotransformer– Current Reduction: Primary Impedance

(Primary Resistor, Primary or Neutral Reactor)

– Motor Impedance (Wound Rotor) Two Specialty Types

– Medium Voltage – Four Common Types: A-T-L, Primary Reactor, Neutral Reactor -and- Autotransformer

– Low Voltage - Wound Rotor (Not U.L. Listed)

Motor Starting - cont’d

Eight (+1) Common Low Voltage Starting Types:

Across‑the‑Line (A‑T‑L or Direct‑On‑Line) Part Winding (Half Winding) Start Primary Resistor Start Primary (or Neutral) Reactor Start Wye‑Delta (Star‑Delta) ‑ Open Transition Wye‑Delta (Star‑Delta) ‑ Closed Transition Soft Start / Soft Stop (SCR Phase

Modulation) Autotransformer VFD Ramp-up (and Ramp-down on some)

Motor Starting – cont’dAcross-the-Line (Direct On Line)

Note absence of Motor Overload (O/L) relay.

FullVoltageStart ------------Across-the-Line

Motor Starting – cont’dAcross-the-Line (Direct On Line)

Motor Starting – cont’dPart Winding Start

Note: The Motor Must be Wound Specifically for Part Winding Starting.

Part Winding Start

Motor Starting – cont’d

Part Winding Start

Motor Starting – cont’dPrimary Resistor Start

Note: Starting KW higher than ATL starting.

Motor Starting – cont’dPrimary Resistor Start

Note: 65% Resistor Impedance is

1.24 - 0.40 = 0.84 pu

Motor Starting – cont’dPrimary Reactor Start

Primary Reactor Start

Motor Starting – cont’dPrimary (or Neutral) Reactor Start

Note: 65% Reactor Impedance is

1.54 – 1.00 = 0.54 pu

Motor Starting Torque Comparison

Curves B, C & D are at 65% Motor Starting Voltage(Reference Source Credit on Next Slide)

“0”“0”

Motor Torque Comparison – cont’dA=ATL, B=A.T., C=Pri. Res., D=Reactor

Gerhart W. Heumann (G.E.), “MagneticControls of Industrial Motors”, Wiley & Sons.

Motor Starting – cont’dPrimary (or Neutral) Reactor Start

Wye-Delta Open Transition

Motor Starting – cont’dWye-Delta Open Transition

LPM Module = Leading Phase Monitor®

First Half Cycle Offset Waveforms

2.83 x LRA = 6 x 2.83 x FLA = 17.0 x FLA Maximum Theortical This curve shows starting a motor

which still has BACK EMF (voltage) present.

Motor Starting – cont’dWye-Delta Open Transition

Motor Starting – cont’dWye-Delta Transition Hazard

ClosedLeading

Lagging

Motor Starting – cont’dWye-Delta Closed Transition

Wye-Delta Closed Transition

Motor Starting – cont’dWye-Delta (Open or Closed Xtn.)

Wye-Delta Starting; Truths and Myths

Page 1 of 4


Page 2 of 4


Page 3 of 4


Page 4 of 4

Motor Starting - cont’dSoft (Solid State - SCR) Start

Soft Start (Solid State - SCR)

Motor Starting - cont’dSoft (Solid State - SCR) Start

Motor Starting - cont’dAutotransformer Start

Autotransformer Start

Motor Starting - cont’dAutotransformer Start

Motor Starting Characteristics

Parameter Chart Fire Pump Starting Type Characteristics - for - Electric Fire Pump Motors and Controllers

Starting Characteristics (at Stall) -- Typical Values -for- Fully Load Pump (1) Starting Starting Starting Accelerate Motor Motor Amps Amps Starting Power Starting Full Load Type Contactors Closed & KVA & KVA Power % F.L. Torque to Starting Type Note Note (3) Transition % LRA % FLA Factor Note (4) % ATL Full Speed Notes Across-the-Line Any 1 N/A 100% 600% 40% 240% 100% Yes (a)

Part Winding Special (2) 2 Yes 65 390 40 156 48 Usually (b) Primary Resistor Any 2 Yes 65 390 80 314 42 Yes (c)

Primary Reactor Any 2 Yes 65 390 28 111 42 Yes (c) Neutral Reactor 6/12 Lead 2 Yes 65 390 28 111 42 Yes (c)

Wye-Delta Open 6/12 Lead 3 No 33/100 200/600 40 80/240 33 No (d) Wye-Delta Closed 6/12 Lead 4 Yes 33/100 200/600 40 80/240 33 No (d)(e)

Soft Start/Stop Any 1/2 Yes 40/67 240/400 Varies Ramps 16/44 Yes (f) Autotransformer Any 3 Yes 46 276 40 110 42 Yes (c)(g)

See File: Motor-Start-Char.doc

Motor Starting Characteristics Chart Notes (1) Refer to Factory details. (2) Part Winding Motors must be wound specifically for this service. Some motors may not

accelerate to full speed in the starting mode. See Note (b). (3) Units with two or more contactors have two basic steps (Accelerate & Run) with steps three

and four being for transitions. (4) Starting KW Power as a percent of motor full load power requirement. (a) Also called "A-T-L" or Direct-On-Line. Motor Power Factor taken as 40%. Other values

shown are due to the effects of the controller. (b) Part Winding Parameters vary with the motor. Starting Amps & KVA vary from around

60% to 70%, Starting Torque from around 45% to 50%. The motor can start a fully loaded pump if it has no large torque dip or cusp. See the text discussion on Part Winding Starting for details.

(c) Figures are for tap set at 65% which yields a motor voltage of 65% of line (mains) voltage. (d) The Dual Figures are for Starting and Transition. The transition values are to finish

accelerating a fully loaded pump. Examples include deluge or open systems, re-starting a fully loaded pump after a power failure or interruption, and failure of another pump feeding the same system.

(e) Ignores the momentary transition resistor loads. (f) Varies with pump load and particular Soft Starter used. Values shown are initial and

maximum for a typical fully loaded pump. MCS uses the second (Start) contactor for isolation. Others use only the Bypass contactor.

(g) The 46% Starting Amps & KVA figures include the Autotransformer exciting current.

Motor Starting Characteristics

Parameter Notes to Chart

V. Motor Running TypesConstant Speed Running Full Voltage Running

- Synchronous Speeds (3,600 RPM & etc.)- Slip Frequencies - Running (Rated)

Speeds Motor Lead Wire Running Currents

- Three Lead = Full Motor Current- Six Lead Parallel Run (Part Winding

Start)= 50% of FLC per set

- Six Lead (Wye-Delta Start)= 58% (57.7%) of FLC per set

Motor Running - cont’d

Variable Speed Running Wound Rotor Control

- Changes Motor Secondary Impedance -and-

- Motor Torque Curve Variable Frequency - Variable Speed

Control (VFDs)- Changes Motor Torque and Current

Curves

- Changes Motor Synchronous Speed –and-

- Changes Motor Running (Loaded) Speed

Wound Rotor Speed-Torque Curves

(Reference Source Credit on Next Slide)

Wound Rotor Speed-Torque Curves

- Flipped and Rotated -

Gerhart W. Heumann (G.E.), “Magnetic

Controls of Industrial Motors”, Wiley & Sons.

VFD = Motor Running Only (No Motor Starting Region)

Starting Region

(Reference Only)

Variable Speed ControllersPower Circuit Schematic

. .* Was Optional

Variable Speed Control

VI.Motor Wiring – Motor Lead Configurations (Fourteen)

Three Lead – Three Coil

(Single Voltage) (T1‑T3) Six Lead – Three Coil

– Wye Running (T1‑T3 & T4‑T6)– Delta Running (T1‑T3 & T4‑T6)

Parallel Run (Six Lead - Six Coil)– T1‑T3 and T7‑T8 - or -– Both Sets Labeled T1‑T3

Motor Lead Configurations3 Lead – 3 Coil - Wye Running

Motor Lead Configurations3 Lead – 3 Coil - Delta Running

Motor Lead Configurations6 Lead - 3 Coil - Wye Running

Motor Lead Configurations6 Lead – 3 Coil - Delta Running

6 Lead – 6 Coil - Wye RunningParallel Running

6 Lead – 6 Coil - Delta Running Parallel Running

Motor Wiring – cont’d

Nine Lead (Dual Voltage) (T1‑T9)– Wye Wound– Delta Wound– Suitable for Part Winding Start ?

Twelve Lead (T1‑T12)– Dual Voltage– Single Voltage (Parallel Run)

9 Lead - 6 Coil - Wye RunningSeries Running

9 Lead - 6 Coil - Wye RunningParallel Running

9 Lead - 6 Coil - Delta RunningSeries Running

9 Lead - 6 Coil - Delta RunningParallel Running

12 Lead - 6 Coil - Wye RunningSeries Running

12 Lead - 6 Coil - Wye RunningParallel Running

12 Lead - 6 Coil - Delta RunningSeries Running

12 Lead - 6 Coil - Delta RunningParallel Running

Typical 12 Lead Motor Wiring Diagram

Courtesy of Marathon Electric

Starting Methods -vs- Motor Types

Table M-04 - Motor and Starting Types

Starting Type Motor Type Starting Type Motor Type

Full voltage Standard/Any Primary Reactor Standard/Any

Part Winding Part Winding Primary Resistor Standard/Any

Wye Delta - Closed Delta Run Autotransformer Standard/Any

Wye Delta - Open Delta Run Soft Start (SCR) Standard/Any

Neutral Reactor Wye Running Wound Rotor Wound rotor

Motor Description (a) Starting Method(b)

Run Type Number of Leads Part Winding

Wye (Star) Delta(c)

Neutral Reactor

"Other 5" Figure

Wye Run Three Lead No No No Yes 7-4

Delta Run Three Lead No No No Yes 7-5

Wye Run Six Lead, Single Coil No No Yes Yes 7-6

Delta Run Six Lead, Single Coil No Yes No Yes 7-7

Wye Run Six Lead Parallel Some(d) No No Yes 7-8

Delta Run Six Lead Parallel Some(d) No No Yes 7-9

Wye Run Nine Lead Series No No Yes Yes 7-10

Wye Run Nine Lead Parallel Some(d) No No Yes 7-11

Delta Run Nine Lead Series No No No Yes 7-12

Delta Run Nine Lead Parallel No(e) No No Yes 7-13

Wye Run Twelve Lead Series No No Yes Yes 7-14

Wye Run Twelve Lead Parallel Some(d) No Yes Yes 7-15

Delta Run Twelve Lead Series No Yes No Yes 7-16

Delta Run Twelve Lead Parallel Some(d) Yes No Yes 7-17

Notes: (a) The Motor "Type" (Wye or Delta) is the Running configuration, regardless of how the motor is started. Wound Rotor Motors are not covered in this chart. (b) "Other 5" are: Full voltage (A-T-L), Primary Resistor, Primary Reactor, Soft Start and Autotransformer. (c) Either Open or Closed Transition Wye-Delta (Star-Delta). (d) "Some" = May be used only of the motor is labeled as suitable for Part Winding Starting. (e) The 9 lead "Double Delta" method has unequal currents and is not suitable for standard Part Winding controllers.

Table M-06 -- Motor Suitability

Motor Types -vs- Starting Types

VII. Induction Motors --Installation Considerations Physical

– Location ‑ Ideally Within Site of Controller– Motor Protection: Fire, Security, Other

Hazards– ODP -vs- TEFC– Conduit & Hubs– Environmental

Access – All Sides & Conduit Access Electrical N.E.C. (NFPA 70) ‑ §430 (& §

695)– Conductor Sizing – Incoming & Motor Circuit– Voltage Drops: Start & Run– Cable Impedances and Run Lengths (See NEMA ICS-14)

Motor Installation – cont’d

Environmental Open Drip Proof (ODP) Totally Enclosed Fan Cooled (TEFC) Outdoor Hazardous Locations, Explosion

Proof:– Motor, Controller, Wiring

Other– Salt Air– Wind Blown Sand or Dust– Temperatures– Altitude

Motor Installation – cont’d

Start-up (Commissioning)

Current Measurements Voltage Measurements Estimating Motor Load

– FLA -vs- Voltage– SFA (115%) - Max. Allowed Under

Any Conditions (Temperature, Altitude, Voltage Imbalance) on ANY Phase

Note: NFPA-20 Governs Startup Testing and Procedures

Questions ?

Jim Nasby

Columbia Engineering

847-677-3468

[email protected]

IEEE-IAS 2012.02.18 Presentation - Motor Starting Techniques

Technology

Transcript of IEEE-IAS 2012.02.18 Presentation - Motor Starting Techniques