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Measurements of efficiency for converters and motors in industry reality

Sinan Altındağ, R&D Manager - 07.10.2014 – Motor Summit’14 EMSA Workshop - Zurich

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GAMAK Turkey’s largest Electric Motor Manufacturer Total Closed Area 60.000 m2, field 330.000 m2 Approx. 1,2 million motor production capacity Mainly Squirrel Cage Motors from 5 W to 1 MW Approx. 200 CNC Machines Vertically integrated production, producing every part of motor in-house, including wire-enamelling All dies and molds are produced in our Die-Shop 900 employees

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GAMAK Motor Test Laboratory

Power Analyzer High accuracy 0.03%

Induction regulator – input 400 V, output up to 800 V

Torque transducer High accuracy 0.05%

Cage induction motor controlled by regenerative inverter

from 5 W to 900 kW from 110 V to 11 kV

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Fully Automatic Test System

Fully Automatic Test System controlled by PC – Labview-application software - Avoid Operator effect - Test reports - also prepared automatically

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Torque Measurement Moving average taken from original measurements

Torque fluctuation

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Efficiency Measurement on-site

Mains

Inverter

Motor LOAD

Input Power Measurement; - Current, Voltage, Power Choosing the right instrument; - Power Analyzer - Network Analyzer - Electricity Meter

Output Power Measurement; - Torque, Speed

Choosing the right instrument; - Torque transducer - Strain gauge

Transmission

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Input Power Measurement Comparison of difference between IE1 and IE3 motor efficiencies will be examined under both laboratory and on-site application conditions, for both mains and inverter supplied motors ; The main difference on test setup is the power analyzer ;

Power Analyzer High Accuracy; 0.03%

Network Analyzer Accuracy; Current&Voltage 0.5%, Active Power 1%

Electricity Meter Accuracy; 1%

A B C

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Comparison of Test Results for IE1 and IE3 motors – Under Laboratory Conditions

Motor Type

Rated Current

(A)

Rated Speed (rpm)

Copper Losses

(W)

Iron Losses

(W)

Rotor Losses

(W)

Friction Losses

(W)

Stray Load

Losses (W)

Total Losses

(W)

Full Load Efficiency

(%)

IE1 1.1 kW 4P 2.535 1408.0 152.6 49.1 73.6 4.5 20.2 299.9 78.59

IE3 1.1 kW 4P 2.357 1433.0 86.6 41.7 52.7 10.4 13.2 204.7 84.36

Efficiency is calculated according to indirect method where the additional load losses are determined from exact measurements at different load points – IEC 60034-2-1:2014

95.2 W difference in total losses

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Comparison of Analyzers

C

A

B

Motor Type

Rated Current

(A)

Rated Voltage

(V)

Power Factor

Total Losses

(W)

Full Load Efficiency

(%)

IE1 1.1 kW

4P

2.535 398.37 0.79 299.9 78.59

2.57 402.4 0.783 301 78.55

- - - 302 78.48

IE3

1.1 kW 4P

2.357 402.89 0.796 204.7 84.36

2.37 403.9 0.792 207 84.21

- - - 209 84.09

B

C

Analyzer Type

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Natural Load Tests – Fan Application Comparison of IE1 and IE3 motors on Fan Load. Measurements made by Network analyzer ;

Motor Type Load Current Speed (rpm) Input Power (W) Air Velocity (m/s)

IE1 – 1.1 kW 4P 2.5 1410 1379 24

IE3 – 1.1 kW 4P 2.38 1430 1342 24.4

Saving is less, but makes more work

Due to higher speed, IE3 motor is overloaded while the IE1 is underloaded

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Input Power Measurement for Inverter Duty

Mains

Inverter

Motor LOAD Transmission

Inverter Input - Even simple analyzers can be used to measure inverter input power

Inverter Output - Simple Analyzers

cannot be used - High bandwith

required (DC upto 100 kHz)

Cabling and grounding is important for test setup – Shielded cables should be used between motor and inverter

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Inverter Duty – Test Results

Mains Inverter Motor

Input Power (W) 1357 1360

System Efficiency (%) 81.29 81.18

Input Power (W) 1335 -

Motor Efficiency (%) 82.7 -

Analyzer A B

Analyzer A B

1.1 kW 4P IE3

LOAD

Output Power 1104 W

Losses increases by around 26 W when compare with mains supplied

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Natural Load Tests – Inverter Driven Fan Application Comparison of inverter driven IE1 and IE3 motors on fan load. Measurements at two different frequency points – 25 Hz and 50 Hz ;

Motor Type Load Current (A) Speed (rpm) Inverter Input Power (W)

Air Velocity (m/s)

IE1 – 1.1 kW 4P 2.52 1410 1400 24

0.714 710 272 12

IE3 – 1.1 kW 4P 2.45 1431 1384 24.4

0.655 718 244 12.2

Hz

50

25

50

25

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Output Power Measurement Testing output power on site; - Torque transducers are not applicable and practical to use on site - Strain gauges are practical more for bigger motors due to the need of a space on motor shaft to fix it.

- Accuracy of strain gauges is around 0.1%

Motor Transmission

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Comparison of Torque Transducer and Strain Gauge – 250kW 4P Motor Test

Strain Gauge (Nm)

Torque Transducer

(Nm) Deviation (%)

331 318 -4,088

650 640 -1,563

964 960 -0,417

1280 1275 -0,392

1590 1600 0,625

1917 1910 -0,366

2225 2240 0,6696

2550 2560 0,3906

2862 2880 0,625

Deviation = (Torque Transducer – Strain Gauge) / Torque Transducer

Rated Torque Measurement

Strain Gauges are fitted on the shaft, therefore shaft material data and diameter is needed to do calculations

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Testing Strain Gauge on a Ball Mill Application 710 kW 4 Pole Motor

Speed (rpm)

- Ball Mills are used to grind the raw material. Load is unbalanced - Mechanical Impact coming from load side - Not possible to make stable measurements due to nature of load

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Input Power Measurement On-Site - For a simple motor input power measurement, it is possible and practical to use low accuracy analyzers - Not possible to measure motor efficiency on-site for inverter duty running - It is possible to check input power of inverter with low accuracy analyzers

Output Power Measurement On-Site - The most practical way to measure output power is to use strain gauge, however it is more practical to use for big size

motors i.e. over IEC frame size 315 - There are some other measurement devices that only measure input power and then calculate the output, but it is important to input correct parameters which should be known beforehand

In case of using current transformers, be sure for the accuracy not worse than 1%

Its accuracy depends on how proper it is applied and nature of load