Download DYNAMIC LOAD RESPONSE

DYNAMIC LOAD RESPONSE:
As a result of the impressed inverter
output wave form.
Presenter: Dr Gawie van der Merwe
Introduction
 Single frequency inverters used for power
conversion of 12 or 24V DC to 220V AC
 Output waveform varies between
– Sine wave, Square wave, Modified Sine wave
 Various loads respond differently due to the
voltage supply:
– Examples: Single phase motors, fluorescent lights,
computers, Microwave ovens, etc
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
Experimental setup
 Sine wave supply was generated using
an Escom supply line.
 A H-Bridge inverter, with a varying DC
link was used- to simulate square wave,
and modified sinewave (refer sketch on
next slide)
 Loads tested:
VARIABLE
DCLINK
– Fluorescent lights with
electronic ballast
– 700W Drill
– Single phase induction
motor
– Microwave oven
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
OUTPUT
Test circuit and supply voltages
400
300
200
100
0
-100
-200
-300
-400
Sine
230V
250V
275V
310V
THD CONTENT OF QS SIGNAL
230
PERCENTAGE OF MAIN HARMONIC
1
0.8
230
0.6
250
275
0.4
310
0.2
0
Copyright:
Dr Gawie
van der
Merwe7 www.planmypower.co.za
1
3
5
9
11
HARMONIC
13
15
700W Drill
Square Startup Current Running Current
Peak (RMS)
THD
Sine
100ms
20
1.75A
% Value
QS 220V
80ms
11.2A
1.3
% Value
QS 250V
60ms
18A
1.65
% Value
QS 275V
60ms
19
1.7A
% Value
20A
1.7A
% Value
QS 310V 140ms
 Result: Difference between QS with Peak in
area
of 275V approx the same as sinewaveCopyright: Dr Gawie van der Merwe www.planmypower.co.za
– Higher peak at 310V slower response notable
Electronic Ballast
Sine wave
Copyright: Dr Gawie van der Merwe
Current Harmonic Content
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Current waveform with 220V
Current Harmonic Content
Electronic Ballast
250V
Copyright: Dr Gawie van der Merwe
310V
Current Harmonic content
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Current Harmonic Content
Electronic Ballast
 Electronic Ballast load represents, most
non linear loads, such as DC to DC
converter, computers, etc
 An increase in THD of the current is
noticeable
 QS inverter reduce
lifetime of electronic
ballast fluorescent
lights
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
Electronic Ballast
 Lifetime reduction up to 60%
 Current peak of QS and Sine more or less
the same
 Higher Harmonic content reduce
capacitor lifetime
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
Single Phase Induction motor
 Very applicable application for fridges,
borehole pumps etc.
Start up time
Current
Sinewave
240 ms
9A
220V DC link
580 ms
peak 3,9A
250V DC link
630 ms
peak 6,5A
275V DC link
440 ms
peak 9A
310V DC link
2sec
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
peak 10,5A
Result
Single phase motor warm up when
run by QS
With same load, power consumption
varies
Higher current peak
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
VOLTAGE AND CURRENT
220V DC LINK (MOTOR)
400
6
4
2
0
0
-2
CURRENT (A)
VOLTAGE (V)
200
CURRENT
VOLTAGE
-200
-4
-400
-6
-40
7.2
54.4
101.6
148.8
TIME (10MS/DIV)
VOLTAGE AND CURRENT
600
3
400
2
200
1
0
0
-200
-1
-400
-2
-600
-50
Copyright:
50
Dr 0Gawie van der
Merwe
100
150
www.planmypower.co.za
TIME (10MS/DIV)
-3
200
CURRENT (A)
VOLTAGE (V)
275V DC LINK (MOTOR)
CURRENT
VOLTAGE
Comparative current harmonic
content
Sine
Copyright: Dr Gawie van der Merwe
250V
220V
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275 V
Magnetic Ballast Fluorescent
Lights
Sinewave supply runs lights
When power factor correcting
capacitor is installed, no QS inverter
will run lights
 To run fluorescent light, PF capacitor
must be removed - non standard
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
Microwave Oven
Typical requirement for farmers and
mobile industry.
– Water boiling test
– 1 Liter water
60
1500
40
1000
20
500
0
POWER (WATT)
TEMP VARIATION (K)
TEMPERATURE DIFFERANCE
0
SINE
230V
250V
275V
310
VARIATION IN SUPPLY VOLTAGE
Copyright: Dr Gawie van der Merwe
1 LIT ER WAT ER
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60 SECONDS
300 SECONDS
POWER CONSUMED
Microwave Oven Results
Microwave Oven requires high
voltage peak
Energy transfer of sinewave supply
up to 15% more effective
Low QS wave form has no effect on
working of microwave oven
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
Results & Conclusion
 A wide variation in dynamic response is
visible
 Pure Sine wave is the best overall
 Fluorescent lights & Microwave ovens
prefer higher voltage peak
 Motor warm up due to 3rd and 5th
harmonic is visible
 Delayed single phase motor startup due
to higher harmonics
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za
Summary and future work
The paper presented some load
responses due to the impressed
voltage wave form.
It is clear that the applied wave form
has a influence on the load.
Lifetime reduction test are still
being done.
Copyright: Dr Gawie van der Merwe
www.planmypower.co.za