Test Tools and Troubleshooting Motors- Fluke

Test tools and troubleshooting electric motors Troubleshooting is the systematic elimination of various parts of a system, process, or piece of equipment to locate a malfunctioning part. To locate and correct a motor malfunction quickly, troubleshooting is best performed using the proper test tools. Different types of test tools are used depending on which part of the system is being tested and what information is required to isolate the fault. For example, when troubleshooting a motor and motor control circuit the following test tools can be used: • Non-contact voltage detector is used to determine if conductors or any non-grounded metal parts are energized before touching them. • Digital multimeter (DMM) is used to take basic resistance, voltage, and current measurements. • Clamp-on ammeter is used to take current measurements without opening the circuit. • Megohmmeter is used to detect insulation deterioration. • Non-contact thermometer is used to measure temperature in order to determine circuit overloading, poor connections, or undersized conductors. • Power quality analyzer is used to measure for harmonics on the line, transients, power interruptions and other circuit conditions that can cause component and system faults.

Application Note

Non-contact voltage detector

can be used to indicate if voltage is present in an insulated conductor, or that a non-insulated A non-contact voltage detector is metal part is energized (hot, live) a test tool that gives a visual by a hot conductor touching an indication when voltage is pres- improperly grounded system or ent in a conductor, or other metal part. Touching an energized parts. The tester glows red if metal part can cause an electrical voltage is present. The red glow shock.

ON

3Ø motor OFF

Flexible connection to motor using rubber or plastic covered conductors

Non-contact voltage detector used to check if conductors are energized

From the Fluke Digital Library @ www.fluke.com/library

Digital multimeter (DMM) A DMM is a test tool that measures several different electrical quantities, such as voltage, resistance, or current. Some

such as testing for power loss from blown fuses, excessive current levels from overloaded circuits, and improper resistance from damaged insulation or equipment.

models also include special features for taking minimum/maximum, and relative measurements and/or testing diodes and capacitors. A DMM is required when performing troubleshooting tasks

3 phase motor 480/277 V, Y connected – voltage measurement Phase to Phase L1 to L3

L1 to L2

L2 to L3

4 Measure L1 to L2, L1 to L3, and L2 to L3

AutoHOLD

FAST MN MX

HOLD

MIN MAX

LOGGING

SAVE

RANGE

SETUP

YES

REL

CANCEL

Hz % ms

NO

nS

F

mV ac+dc

AutoHOLD

FAST MN MX

HOLD

MIN MAX

A mA

V

ac+dc

A

V

A mA

dB

dB

L1 L2 L3

SAVE

A A mA

10A MAX FUSED

400mA FUSED

CAT 1000V

SAVE

NO

nS

F

C

A mA

V

ac+dc

A

mV dB

dB

A mA

V

dB

ac+dc

A

OFF

ac+dc

A

OFF

ac+dc

ac+dc

VIEW MEM

VIEW MEM

CLEAR MEM

TEMPERATURE

V

CLEAR MEM

TEMPERATURE

mA A

A 10A MAX FUSED

YES

REL

RANGE

mV ac+dc

A mA

V

ac+dc

V

LOGGING

CANCEL

Hz % ms SETUP

F

CLEAR MEM

COM

MIN MAX

dB

ac+dc

mA A

FAST MN MX

HOLD

C

mV

ac+dc

A

AutoHOLD

NO

nS

VIEW MEM

Set DMM for AC Voltage

YES

REL

RANGE

mV ac+dc

A

OFF

LOGGING

CANCEL

Hz % ms SETUP

C

mV

3

From Power Supply

TEMPERATURE

V

COM CAT 1000V

400mA FUSED

mA A

A 10A MAX FUSED

V

COM

400mA FUSED

5

CAT 1000V

Measure L1 to Ground, L2 to Ground, and L3 to Ground

Voltage jack Common jack

Phase to Ground L3 to Ground

L2 to Ground

L1 to Ground

On

7 Close Disconnect Cover

AutoHOLD

FAST MN MX

HOLD

MIN MAX

Off

YES

REL SAVE

RANGE

AutoHOLD

FAST MN MX

HOLD

MIN MAX

NO

SAVE

A mA

V

ac+dc

A

V

A mA

dB

A A mA

6

10A MAX FUSED

Verify Rating of Overcurrent Devices

400mA FUSED

CAT 1000V

RESET

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Test tools and troubleshooting electric motors

ac+dc

A

OFF

ac+dc

VIEW MEM CLEAR MEM

TEMPERATURE

10A MAX FUSED

V

400mA FUSED

CAT 1000V

Motor

Black Test Lead

A A mA

dB

CLEAR MEM

COM

2

Starter

A mA

V

VIEW MEM

mA A

A

Open Disconnect Cover

Red Test Lead

F

C

ac+dc

ac+dc

TEMPERATURE

V

NO

nS

V

ac+dc

CLEAR MEM

COM

SAVE

mV

A

OFF

VIEW MEM

mA A

A

YES

REL

RANGE

dB

dB

ac+dc

LOGGING

CANCEL

Hz % ms

mV ac+dc

A mA

V

ac+dc

V

ac+dc

MIN MAX

F

mV

A

OFF

FAST MN MX

HOLD

C

dB

dB

AutoHOLD

NO

SETUP

mV ac+dc

C

mV

YES

REL

RANGE

nS

F

mV ac+dc

LOGGING

CANCEL

Hz % ms SETUP

nS

1 Remove Lockout/ Tagout

LOGGING

CANCEL

Hz % ms SETUP

TEMPERATURE

mA A

A 10A MAX FUSED

V

COM

400mA FUSED

CAT 1000V

Clamp-on ammeter A clamp-on ammeter is a test tool that measures current in a circuit by measuring the strength of the magnetic field around a

conductor. Most clamp-on ammeters measure AC, others can measure both AC and DC. The clamp-on ammeter allows current measurements without opening a circuit. The jaws of a

clamp-on ammeter are opened and enclose the conductor under test. The measurement displayed indicates the amount of current drawn by loads connected to the conductor.

Motor running current From Power Supply L1 L2 L3 Disconnect On Motor On

Off To change direction of motor rotation, interchange any two load conductors (power off)

Clamp Meter reading Rated current of motor 20 A

Disconnect

L1

L2

3 Fluke Corporation

L3

L1

L2

L3

Test tools and troubleshooting electric motors

L1

L2

Motor underloaded 9.5 A

Motor fully loaded 20 A

Nameplate 0 % to 95 % of listed listed value value

95 % to 105 % of listed value

L3

Motor overloaded 22 A 105 % + of listed value

conditions. A megohmmeter detects insulation failure or potential failure of insulation caused by excessive moisture, dirt, heat, cold, corrosive vapors or solids, vibration, and aging.

Megohmmeter A megohmmeter is a test tool that detects insulation deterioration by measuring high resistance values under high voltage

L1 L2 L3 PE

Starter From Power Supply L1 L2 L3 Disconnect

ON

Lockout/Tagout Disconnect

T2 Position

T1 Position

RESET

OFF

T1

T2 T3

PE

1 Testing Starter and Cable

Conductors T1 T2 T3 Position

T3

Red Test Lead

Black Test Lead T1

2 Testing Motor

T1 Position

T2 T2 Position T3

T3 Position

Wye-connected low voltage 3Ø Motor

Recommeded Minimum Resistance* Motor Voltage Rating (from nameplate) Less than 208 208 – 240 240 – 600 600 – 1000 1000 – 2400 2400 – 5000

Minimum Acceptable Resistance 100,000 Ω 200,000 Ω 300,000 Ω 1 MΩ 2 MΩ 3 MΩ

* Values for motor windings at 40 °C

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Test tools and troubleshooting electric motors

Stator Windings

Non-contact thermometer Loose, corroded, or dirty electriA non-contact thermometer is a test tool that measures temperature at a single point. Temperature is measured when troubleshooting because the resistance of most materials change as the temperature of the material changes. An increase in temperature decreases the performance of electrical equipment and destroys insulation.

cal connections generate unwanted resistance and heat. The temperature rise at a connection depends on the current flowing through the connection and the resistance of the connection. A temperature rise of 85 °F above ambient temperature indicates a fault that requires routine maintenance. Routine maintenance is performed so that the problem is fixed before it

causes damage. A 100 °F increase requires immediate action. Immediate action involves immediate shutting down of a system and repairing the fault. Resistance in a normal circuit occurs at the load. Resistance in a circuit that has poor connections, corrosion, or other high resistance paths occurs at points other than the load. Infrared meter temperature measurements prevent problems by locating unwanted heat.

Take temperature reading of areas above ambient temperature

Finding Temperature Reading On

What is the temperature reading if the temperature of an area is 145 °F and the ambient temperature is 60 °F?

Off

1. T = Temperature reading – Ambient reading T = 145 – 60 T = 85 °F (Schedule routine maintenance)

Equipment Condition Temperature Difference* 45 60 85 100 * In ° F

Aim meter at area to be measured

Take ambient termperature reading for reference

61

INFR THER AR MO ED ME

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TER

Test tools and troubleshooting electric motors

Indication Light load on circuit Heavy load on circuit Possible problem. Schedule routine maintenance Dangerous problem.

Power quality analyzer A power quality analyzer is a test tool used to obtain and record more valuable troubleshooting data. They can take all the basic measurements that a DMM can take, and also measure harmonics, transients, power, and other electrical quantities and problems.

Power Quality Meter

Voltage or current harmonic selction

MANUFACTURER PE-21 PLUSTM

PREMIUM EFFICIENCY

ORD. NO. 1LA2864SE41

CLASS INSUL SH. END BRG.

MAG. 21.8 FRAME 286T SERVICE 30.00 1.0 3 PH FACTOR 77.5 VOLTS 230 1765 HERTZ 60 DATE CONT 40¡ AMB. CODE NEMA KVA NEMA H DESIGN B CODE G NOM, EFF. 93.6 OPP. END 50BC03JPP3 50BC03JPP3 BRG.

RGZESDI

51-770-642

TYPE HP AMPS RPM DUTY

Current AC Supply

Inverter Duty AC Induction Motor Made in U.S.A.

3Ø Motor

This article is based on material excerpted from Electric Motor Drive Installation and Troubleshooting, Troubleshooting Electric/Electronic Systems, 2nd Edition, Power Quality Measurement and Troubleshooting, and Electrical Motor Controls, 2nd Edition published by American Technical Publishers, Inc. To obtain information on related training products, visit the American Tech web site at www.go2atp.com.

Fluke. Keeping your world up and running. Fluke Corporation PO Box 9090, Everett, WA USA 98206 Fluke Europe B.V. PO Box 1186, 5602 BD Eindhoven, The Netherlands For more information call: In the U.S.A. (800) 443-5853 or Fax (425) 446-5116 In Europe/M-East/Africa (31 40) 2 675 200 or Fax (31 40) 2 675 222 In Canada (800) 36-FLUKE or Fax (905) 890-6866 From other countries +1 (425) 446-5500 or Fax +1 (425) 446-5116 Web access: http://www.fluke.com ©2003 Fluke Corporation. All rights reserved. Printed in U.S.A. 8/2003 2105286 A-ENG-N Rev A

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Test tools and troubleshooting electric motors