Pump Motors Johnson

7/30/2019 Pump Motors Johnson

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1. Understanding pump motors 2

2. Who should know about pump motors? 33. AC electric motor design 44. Typical motor terms 65. Motor cooling and protection 86. What makes an energy-efficient motor? 10

7. Motors for hazardous environments 128. How to select the correct motor 149. How to start and control a motor 1610. Motor maintenance and troubleshooting 18

Glossary 20Other handbooks in the series 22

Contents

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Pump motors


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Understanding the various aspects of pump motors makes it easier to selectand handle motors and pumps correctly and to more efficiently optimizeprocess/system performance.

1. Understanding pump motors

A sanitary pump is always driven by a motor, most commonly an ACelectric motor.

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Examples of pump motors

1. Most motors have the same basic design.2. The most common motor type has an externally mounted fan located on

the back of the motor to cool it during operation.

3. A rotary lobe pump is normally driven by a geared motor due to theneed for low speed.4. Frequency control is the most common way to control a pump motor.

Fig.1.2. Motor cooling (principle)

Fig.1.3. Geared motor (principle) Fig.1.4. Motor/pump control(principle)

Geared motor

Rotary lobepump

Fig.1.1. Motor design (principle)


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Knowing the basic motor terms, various motor types and how to selectbetween them for given pumps, as well as how to install, operate andservice motors ensures that pumps and processes are optimised and thaterrors, damages and personal injuries are avoided. The target groups mayinclude:

2. Who should know about pump motors?

All people in touch with flow equipment during its life cycle shouldknow about pump motors.

1. Process designers, who should know what motor types to select so thatthe pump and process are optimized related to quality and costs.

2. Sales and sales support people, who should know the possibilities andlimitations of pump motors related to given pumps/processes.

3. Field operators, who should know the possible causes of motormalfunction and know how to solve them.

4. Beginners in the flow industry, who should have a basic understandingto work efficiently.

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General design: Typically a Totally Enclosed Fan Ventilated (TEFV) squirrel-cage three-

phase motor.

Normally complies with international directives and standards, e.g. IEC,CENELEC, DIN etc.

A motor is typically fitted directly to a centrifugal pump. A rotary lobe pump normally uses a geared motor due to the need for

low speed.

Design parts:

Motor part Description

Stator housing Includes stator and iron core.Ball bearings Fixed in stator housing.

Carry rotor and motor shaft.Fan Fixed to motor shaft on back of motor.

Cools motor during rotation/operation.

Protected by a fan cap.

Electricalconnection

Connection of voltage supply.

Located on stator housing.

Iron core Located in stator housing.

Consists of thin iron sheets.

3-phase windings located in grooves of iron core.

Motor principle: The stator and the 3-phase windings are designed to produce a

magnetic field in pairs of poles.

The stator is connected to a 3-phase voltage supply.

The magnetic fields of individual phase windings form a symmetricallyrotating magnetic field, called a rotational field.

The speed of the rotational field is called synchronous speed.

3. AC electric motor design

There are many types and brands of AC electric motors available forsanitary pumps. Most motors have the same basic design.

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Fig.3.1. Motor design (principle)

Fig.3.2. Motor for centrifugalpump (principle)

Fig.3.3. Geared motor for rotarylobe pump (principle)

Centrifugalpump

MotorGeared motor

Rotary lobepump

1. Stator housing2. Iron core3. Stator4. Ball bearing5. Motor shaft

6. Fan7. Fan cap8. Cover9. Electrical connection

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Typical motor terms

Term Description

Voltage supply/frequency

Voltage to which the motor should be connectedto produce the rated speed and output power.

Typically 230-690 V, depending on site/location.Affects wiring of motor (star or delta).

Frequency 50 Hz or 60 Hz, depending onlocation.

Output power What the motor develops when connecetd to therated voltage, frequency and phases.

Lower than rated power due to losses in motor.

The motor is a slave of a pump. The pump pullsout the power needed for the duty in question.

Current Current drawn by the motor at the rated power,voltage and frequency.

Motor is OVERLOADED if the actual measuredcurrent is higher than the rated nameplate value.

Rated speed The actual motor speed at full load.

Always lower than synchronous speed due to slip.Cooling Specified by the letters IC according to standards.

Most common is externally mounted fan (TEFV),specified as IC411.

Protection class Specified by the letters IP according to standards.

Two digits specify the degree of protectionagainst dust and water.

The most common are IP54 and IP55.Insulation class Specifies the allowable temperature rise based on

the insulation system.

The most common are class B and class F.

Frame size Physical size of motor as well as certain design

features such as shaft and mounting dimensions.Pole 2-pole (3000/3600 rpm at 50/60 Hz).

4-pole (1500/1800 rpm at 50/60 Hz).

4. Typical motor terms

It is important to know the typical motor terms to ensure correcthandling of AC electric motors.

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Fig.4.1. Voltage supply/frequency (principle)

Fig.4.2. Output power(principle)

Fig.4.3. Rated speed(principle)

230-690 V50/60 Hz

Ratedpower

Outputpower>

Motor losses!

Synchronousspeed

Ratedspeed>

Slip!

Fig.4.4. Insulation class(principle)

Fig.4.5. Frame size(principle)

Motor dimensions!

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Cooling: A motor is heated up during operation, so cooling is required to prevent

damage to the motor.

Cooling is specified by the letters IC (International Cooling) according tostandards.

Cooling codes/methods:

Code Cooling method / description

IC411 Totally Enclosed Fan Ventilated (TEFV).

Cooling by an externally mounted fan.

Most common cooling method.IC410 Totally Enclosed Non Ventilated (TENV).

Self-cooling, no externally mounted fan.IC418 Totally Enclosed Air Over Motor (TEAOM).

Motor cooled by airstream.IC416 Totally Enclosed Forced Cooled (TEFC).

Motor cooled by an independent fan.

Protection: A standard motor is designed to be protected against dust and water.

The degree of protection is specified by the letters IP (International

Protection) and two digits according to standards. First digit specifies the degree of protection against dust and other

particles.

Second digit specifies the degree of protection against water.

The most common protection classes are IP54 and IP55.

Special tropic-proof motors are available for operation in tropicalclimates.

A motor fitted with an anti-condensation heater is recommended for usein long-term damp conditions.

Thermistors are used to protect motor windings from overload due tohigh temperature. Normally used for frequency converter duty.

5. Motor cooling and protection

There are different cooling methods and protection classesavailable for AC electric motors.

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Fig.5.1. Cooling (principle)

Fig.5.2. Protection (principle)

Designation 1st digit 2nd digit

Protection against contactand ingress of foreignobjects.

Protection against water.

IP 54 Water splash does not harmmotor.

IP 55

Protection against partsinside enclosure.Sufficient protection againstdust to ensure satisfactorymotor operation.

Water from nozzle does notharm motor.

Independent/integrated/no

cooling fan!

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General design: An energy-efficient motor produces the same output power but uses less

electrical input power than a standard motor.

The greater efficiency is thanks to higher quality and thinner laminations

in the stator to reduce core loss. The greater efficiency is also thanks to more copper in the slots to

reduce current and resistance losses.

Motor range: Three efficiency classes: EFF1, EFF2, EFF3.

For TEFV, 2- and 4-pole, squirrel-cage induction motors.

For power range 1.1 kW to 90 kW, 400 V and 50 Hz.

EFF3-class motors can be used for intermittent usage.

EFF1 and EFF2 motors are for continuous usage.

6. What makes an energy-efficient motor?

A process with many pumps/motors uses lots of energy.An energy-efficient motor is an effective way to save energy andreduce running costs.

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Fig.6. Energy efficient 2-pole motors (example/principle)

Efficiency (%)Output power

(kW) EFF1

Equal to or above

EFF2

Equal to or above

EFF3

below1.1 82.8 76.2 76.2

1.5 84.1 78.5 78.5

2.2 85.6 81.0 81.0

3 86.7 82.6 82.6

4 87.6 84.2 84.2

5.5 88.6 85.7 85.7

7.5 89.5 87.0 87.0

11 90.5 88.4 88.4

15 91.3 89.4 89.4

18.5 91.8 90.0 90.0

22 92.2 90.5 90.5

30 92.9 91.4 91.4

37 93.3 92.0 92.0

45 93.7 92.5 92.5

55 94.0 93.0 93.0

75 94.6 93.6 93.6

90 95.0 93.9 93.9


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Hazardous areas: Classified into three zones: 0, 1 and 2.

Zone 0: Permanent presence of explosive gas-air mixture, no motorsmust be used.

Zone 1: Incidental presence of explosive gas-air mixture.

Zone 2: Accidental presence of explosive gas-air mixture. Areas not classified as Zone 0, 1 or 2 are safe areas.

Temperature class: Six temperature classes: T1, T2, T3, T4, T5, T6.

The motor temperature class must be compared with the max. gasignition temperature before usage.

The temperature class is specified on the motor nameplate.

Gas group: Motors are certified and classified according to their gas group.

Group I: For coal mines, with the risk of methane gas.

Group II: For explosive atmospheres other than mines.

Group IIA, IIB, IIC: IIC is highest rating (a higher rating can be used in alower category).

The gas group is specified on the motor nameplate.

Motor types: Non-sparking: Ex nA, EEx nA.

Increased safety: EEx e.

Flameproof enclosure: EEx d, EEx de.

Dust Ignition Protection (DIP).

7. Motors for hazardous environments

A motor for hazardous environments has a special design that isidentified on the motor nameplate and by test reports.

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Fig.7.1. Temperature class (principle)

Fig.7.2. Classification summary (principle)

Temperatureclass

T1 T2 T3 T4 T5 T6

Max. gas ignitiontemperature C

450 300 200 135 100 85

Max. temperaturerise of motorsurface K

155 155 155 90 55 40

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General: Most motors will do fine on a centrifugal pump thanks to affinity laws.

Motors are typically fitted directly to centrifugal pumps.

A positive displacement (PD) pump requires caution. It is important to

follow certain steps to successfully select the correct motor. A positive displacement pump normally requires a geared motor.

Special considerations regarding PD pumps: What is the max. required pump speed and power required at that speed?

What is the min. required speed and power required at that speed?

If the ratio is higher than approx. 7:1 (may vary for different motor brands),it is recommended to select a special converter duty that can handle therequired speed range or over-speed to increase the effective speed range.

How is the atmosphere that the motor is to be located in?

What is the duty cycle (how many hours per day will the motor beoperating)?

Selection criteria: Select a suitable motor configuration based on the guidelines below and on

the recommendations of motor/pump suppliers.

Brand name, if any preferences.

Voltage supply and frequency, special combination of the two. Required max./min power.

2- or 4-pole (3000/3600 rpm or 1500/1800 rpm).

Max./min. speed of geared motor for PD pump.

Frame type (IEC metric or US Nema C) and frame size.

Flanged- and/or foot-based motor.

Cooling type, protection class and insulation class.

Special motor (high inlet pressure, energy efficient, flameproof, stainlesssteel etc).

Motor for frequency converter duty.

8. How to select the correct motor

As there are different motor demands for different pump types,it is important to have all necessary pump and process data toensure correct motor selection.

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Fig.8. Motor selection process(guidelines only)

Selection/

specification:

Get all motorinformation

andsite/runningconditions

3.

- Standard motor- Larger standard

motor- Rewound motor(All motors withrevised nameplate)

Get pressureconditions:

2.

- Supply voltage- Frequency- Max./min. power- Max./min. speed- Speed ratio for

geared motor- 2- or 4-pole

Special combination ofvoltage/frequency?

Special motorbearings

Select according toreccomendations ofpump/motor suppliers

- Brand type/name- Frame type/size- Flanged- and/or foot-

based- Cooling, protectionand insulation class

- Energy-efficient- For hazardous duty- Converter duty- Duty cycle- Options- Other

1. Select pumptype/size:

High inlet pressure?

Electrical data


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Direct starting: Simple starting method.

The motor is connected directly to the mains supply.

Results in high starting current, often up to 8 times higher than ratedcurrent.

Normally used for motors fitted on centrifugal pumps and liquid-ringpumps where the starting time with high current normally is short.

Star/delta starting: Star and delta are two ways of connecting a 3-phase single-speed

motor.

The starting current is reduced by starting the motor in star connectionand then changing to delta connection.

Often used for high viscous pumps like rotary lobe pumps where thestarting time is longer.

Soft starting: Device which provides smooth start with limited starting current.

Automatically adapts motor voltage to requirement in question.

Can be done with a frequency converter.

Often used as both soft starting and soft stopping to avoid pressureshocks.

Motor speed control: Multi-speed: Normally 2-speed, e.g. a 3000/1500 rpm motor.

Variable voltage control: Normally a 4-pole motor with special design.

Frequency control: For most motors, most common method, externalunit or integrated in motor.

9. How to start and control a motor

There are different ways to start and control AC electric motors,depending on the motor type, motor size and process conditions.

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Fig.9.1. Direct starting ofcentrifugal pump(principle)

Fig.9.2. Star/Delta starting ofa rotary lobe pump(principle)

Fig.9.3. Soft starting withfrequency converter(principle)

Direct starting!

Fig.9.4. Motor with integraredfrequency converter(principle)

Fig.9.5. Two-speed motor(principle)

Avoid pressureshocks!Frequency

converter

3000 rpm/1500 rpm

Frequencyconverter


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General maintenance: Regular inspection of free ventilation airflow, condition of shaft seals and

bearings, condition of connections and mounting.

Manual or automatic lubrication of motors with regreasing nipples

according to instructions. Special caution/lubrication intervals for frequency converter duty.

Most common motor failures:

Failure Possible cause/remedyMotor does notstart

Blown fuse, incorrect supply, overloading.

Replace fuse, connect correctly, reduce load.Noise and

vibration

Worn parts, misalignment, out of balance.

Check/replace parts, realign, rebalance motor.Overheating Overload, incorrect ventilation, worn parts.

Reduce load, check ventilation, replace parts.Incorrect rotation Incorrect sequence of phases.

Reverse connections at motor or switchboard.Motor stalls Open phase/circuit, low voltage, overload.

Check lines/circuit, connect correctly, reduce load.Insufficient speed Low voltage, high starting load, broken/loose rotor.

Connect correctly, check motor load at start,replace rotor.

Motor draws highcurrent

High load, low voltage during start, worn rotor.

Reduce load, check resistance/wire correctly,replace rotor.

Hot bearings Worn shaft, misalignment, insufficient lubrication,overloaded bearing.

Replace shaft, align correctly, lubricate correctly.

10. Motor maintenance and troubleshooting

A motor should be serviced and repaired as instructed. Motor failureshould be solved by having all necessary information to do efficienttroubleshooting.

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Fig.10.1. Noise and vibration(principle)

Fig.10.2. Overheating(principle)

Fig.10.3. Incorrect rotation(principle)

Fig.10.4. Insufficient speed(principle)

Replace parts!Realign/rebalance!

Reduce load!Check ventilation!

Replace parts!

Reverse connections!

Connect correctly!Check motor load!Replace rotor!

n

Fig.10.5. Hot bearings (principle)

Replace shaft!Allign correctly!

Lubricate correctly!


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Centrifugal pump Rotodynamic pump type. The most common pumptype thanks to relatively low purchase cost and manytypes. Typically used for non-viscous fluids.

CIP Cleaning In Place (cleaning without dismantlingequipment first).

Diaphragm pump Positive displacement pump type operated by airpressure.

Flow equipment Equipment used in flow systems. Examples are heatexchangers, pumps, valves, tubing, fittings and tankparts.

Fluid Liquids/media (non-solid and non-gas) processed inflow systems.

Frequency converter Electronic device to regulate speed of an electric

motor. Common and economical way to controlpump performance.

Geared motor Motor fitted with a reduction gear to the motor shaftto reduce the output speed at the gear shaft.Normally used for positive displacement pumps.

Liquid-ring pump Rotodynamic pump type. Similar to a centrifugalpump but with a special impeller/casing design so

that it can pump aerated fluids, such as CIP return.

Output power Power developed by the motor when connecetd torated voltage, frequency and phases.

Piston pump Positive displacement pump type operated by airpressure.

Pressure Force per unit area.

Glossary

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Pressure shock Result of change in fluid velocity.

Rotary lobe pump Positive displacement pump type with two counter-rotating rotors, normally driven by an electric motor.

Rated speed Actual motor speed at full load.

Rotor Mechanical part in a pump that is fitted on apump/motor shaft. Transfers fluid and builds up fluidpressure during rotation.

Screw pump Positive displacement pump type driven by anelectric motor.

Stator housing Stationary part (housing) of a motor. Forms arotational magnetic field which rotates the rotor.

Viscosity Indicates how thick or thin a fluid is.

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22

Other handbooks in this series

1. Pressures in flow systems2. Cavitation

3. Fluid properties4. Pumps for sanitary processes

5. Centrifugal pumps

6. Sizing centrifugal pumps

7. Rotary-lobe pumps

8. Sizing rotary-lobe pumps

9. Pump motors

10. Pump-shaft seals

11. Troubleshooting pumps

12. Flow control

13. Materials for flow equipment

14. Valves for sanitary processes

15. Single-seat valves16. Mix-proof valves

17. Regulating valves

18. Troubleshooting valves

19. Valve automation

20. Standards and regulations


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