How to use a
SKiiP - Tester
Application note
Bild 1:
Bedienungsanleitung
Application Note - how to use
type:
version:
document:
date:
L23005
1.1_eng
1.1
30.08.2013
 Ing. Büro M.Billmann 08/2013
Lerchensteige 10 • D - 91448 Emskirchen
Telefon +49-(0)9104-8235-88 • Fax +49-(0)9104-8235-89
email: [email protected]
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 30.08.2013; M.Billmann; 1/16
ING. BÜRO M.BILLMANN
Semikron SKiiP Tester Manual Control Unit
E: secondary side celvin measurement
F: 41/2 digit voltmeter, ext
G: primary side
SKiiP interface,
wired or optical
A: 24VDC
supply input
B: SKiiP I / II / III
supply select
+24V; +15V; ±15V
H: digital I/O status, LED
2
1
3
C: V CE up to 170V
V F at 1.3A DC
K: pri/sek monitor
5
4
D: PWM signal
generation
I: pri analog signal monitor
6
7
10
8
9
11
L: PWM input
signal matrix
technical details may change without notice!
sketch: front panel elements
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 30.08.2013; M.Billmann; 2/16
Functional description
Front side elements and connectors
A:
Supply input for auxiliary power supply 24VDC
B:
Selector for SKiiP supply
C:
Selector for VCE (IGBT) VF (Diode) measurement
D:
PWM signal generator, ≈ 10 kHz or permanent (CW) signal
E:
Interface for SKiiP secondary side power terminals
F:
Connector for external DVM
G:
primary side SKiiP interface GB/GH/GD,
wired or optical
H:
Digital I/O status PWM SKiiP input signals
I:
Selector for monitoring analog primary side SKiiP signals
K:
Selector monitoring primary / secondary signal monitoring
L:
PWM signal matrix 2 PWM into 6 SKiiP inputs
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 3/16
Contens
1.
About this document
2.
Used symbols and shortcuts
3.
How to prepare a SKiiP tester
4.
How to use
5.
Test setup – SkiiPs with DC link attached
6.
How to proceed on site to test a SKiiP
7.
Primary side standby current consumption
8.
Status LEDs
9.
Primary side 10kHz PWM current consumption
10. Primary side steady ON current consumption
11. Primary side analog signals
12. Summary - Primary side monitoring
13. Secondary side monitoring - SKiiP as standalone unit
14. Summary - Secondary side monitoring
15. Additional hints - Calibration
16. Service
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 4/16
1.
About this document
This application note describes
- a practical example
- how to use the SKiiP Tester
- how to identify weak SKiiPs
with the SKiiP Tester L23005
This document is targeting at the following persons:
- Professionals in power electronics
- Electronic field engineers involved in finding and replacing
SKiiPs on site.
2.
Used symbols and shortcuts
note
Notes will highlight advantages of certain operation modes to
bring out the maximum efficiency of the unit.
warning
Warning notes: Read them carefully and follow those
instructions.
Warning notes shall prevent danger and will help to prevent
damage of the unit or the device under test.
3.
How to prepare a SKiiP tester
There are many different types of SKiiPs in the field, worldwide. Wired
signal, fiber optical signal, 14-/20/26-pin DIN 41651 primary interface, DSUB interface and customized units. Therefore the standard delivery of a
SKiiP tester is completely functional, including a power supply, but without
the connection cable from tester to SKiiP primary side. A separate voltmeter
has to be attached as well.
note
Service personal needs to assemble an adapter cable from
the SKiiP tester to the SKiiP variants used in their
applications.
The SKiiP tester provides DIN41651 pinout for flat cable in 14pin, 20-pin, and 26pin referring to the SKiiP datasheets.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 5/16
4.
How to use
The SKiiP Tester L23005 is a manually operated, handheld unit designed for
electrical implementation between a power supply, a digital voltmeter and a
SKiiPpack to be tested. It enables fast and easy access to monitor the SKiiP
behaviour under various conditions applied.
The SKiiP tester can be operated at two levels of inspection severity:
4.1 SKiiP with DC Link and AC attached [SKiiP to be tested is not
removed from the system and still part of the inverter]
 No access to power terminals, only monitoring of primary side is
possible.
From our experience this provides an 85% chance to detect a SKiiP
malfunction in very fast time. No removal from the inverter is needed.
Just disconnect the primary side interface towards the inverter and
connect the primary side cable from the SKiiP Tester.
warning
4.2
Never connect a SKiiP Tester to a SKiiP while DC link voltage
is present!
Never connect a SKiiP Tester to an inverter system that is not
completely shut down, disabled and discharged!
Remove the AC power terminal connection!
Use qualified personnel only!
SKiiP as standalone unit [SKiiP is removed from inverter and access
to all, even power terminals, is possible].
 Monitoring of primary side and power terminals possible.
From our experience this provides a >95% chance to detect a SKiiP
malfunction in reasonable time. After removal from the inverter many
companies collect their possibly faulty SKiiPs in repair centres.
In addition to the fast test of the primary interface described above
now the secondary power silicon can be tested for parameters as:
- Breakdown voltage (per IGBT and freewheeling diode)
- IGBT ON Switching (by pressing the “permanent ON A or B” buttons.
- Vce_ON (IGBT) at roughly 1.5Adc
- Vf at roughly 1.5Adc (diode conduction)
From our experience even slightly damaged breakdown voltage curves
of silicon chips can be detected with the internal source of 170V/50µA.
Once the voltage drops below 150Vdc there probably is a problem
inside the SKiiP.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 6/16
Note
Some SKiiP sections have the “U-option” with DC-link voltage
measurement (mostly located parallel to the DC power
terminals of HB2 of a SKiiP). As this is an additional load to
the tester´s internal 50µA source some 5-10 volts lower are
expected. Those sections are non-faulty, please double check
a possible DC-link measurement option before thinking of this
SKiiP as faulty.
If the SKiiP to be tested is standalone just connect the primary side
interface with cable from the SKiiP Tester and attach DC & AC power
terminals with the cables that are inside the standard Tester delivery.
Repeat secondary side tests with every SKiiP section (2-/3-/4-fold
SKiiP BG, GD, GH).
5.
Test setup – SkiiPs with DC link attached
Much time is needed to replace a suspicious SKiiP with a new one on site.
If the original unit is not faulty lot of time is wasted and unnecessary rejects
towards the SKiiP supplier are the consequence.
warning
Never connect a SKiiP Tester to a SKiiP while DC link voltage
is present!
Never connect a SKiiP Tester to an inverter system that is not
completely shut down, disabled and discharged!
Remove the AC power terminal connection!
Use qualified personnel only!
Note
First of all - always perform a visual inspection of the
suspicious SKiiP. If mechanical damage, debris, or traces of
explosion are visible an electrical check is not needed to
identify the SKiiP as broken.
6.
How to proceed on site to test a SKiiP
1.) Make sure the inverter is completely powered down, discharged and
accessible safe (same procedure as if you wish to change a SKiiP).
2.) Unplug the primary side wiring from the d.u.t. SKiiP (device under test)
3.) Power up the SKiiP Tester with its power supply (or with any 24Vdc
supply that is current limited to <3A)
4.) Connect a digital voltmeter in auto range voltage mode (200.0mV to
200.0 V should be within the auto range option)
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 7/16
Note
Spare cables are standard computer LAN cables. Spare parts
can be found everywhere in the world. Cable length is a minor
issue, due to Kelvin measurement.
Note
The position of the cables towards the SKiiP tester is not
relevant. Any 8-pin cable will operate in any of the three
positions in the SKiiP Tester. The functions DC terminal, AC
terminal or voltmeter output is chosen automatically.
Note
The SKiiP tester will work with any 24V DC supply of 1.2A or
more, center pin positive. If a SKiiP is in primary side short
circuit, the 24V supply will feed this short circuit through the
SKiiP tester. The tester´s internal 100mOhm shunt will be
damaged if your 24Vdc supply exceeds 3Adc.
7.
Primary side standby current consumption
All knob / button numbers in the following parts refer to the sketch
“front panel elements” on page 2.
5.) Turn the supply knob [1] towards the SKiiP in OFF position (left turn
knob in upper row facing downwards).
6.) Power up your digital multimeter, (set to voltage auto range mode)
7.) Connect the primary side cable from the SKiiP Tester to the d.u.t.
SKiiP, use a type of cable & fiber optics that meets your SKiiP version
Note
Some SKiiPs use a D-SUB connector instead of a DIN41651
14-pin or 26-pin connector. You may get an easy adaption by
using a press-fit D-SUB connector and attach it on the flat
cable.
8.) Turn the right turn knob of the lower row [5] into position “primary
signals”.
note
Always start with the primary side power consumption in
standby and under input signals ON & 10kHz. There is a
chance of > 80% to detect a fault. If a fault is identified there is
no need to complete the test matrix and additional time is
saved.
9.) Turn the middle turn knob of the upper row [2] in position “24V path”
10.) Turn the turn knob of the upper row [3] into position “I_supply”.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 8/16
Now the tester is ready to monitor SKiiP current consumption under various
input command conditions.
11.) Power up the d.u.t. SKiiP by turning the left turn knob [1] of the upper
row into position “24V”.
Now you see the power consumption of the SKiiP under test at 24Vdc
supply in standby condition. No PWM signals are applied; all IGBTs are in
OFF status. If the value indicates “good” or “bad” must be decided by a
reference value from a “good” sample, or in comparism to a neighbour
SKiiP´s value.
The internal shunt has a value of 100mOhm. Thus a current consumption of
e.g. 187.3 mA will display in 18.73mV. Allow a settling time of some seconds
and expect a little change in consumption due to the circuit heating up.
Note
There are many variants of SKiiP in the field. Their power
consumption varies from some possible minor changes within
date-code, component variance and mostly ambient
temperature. Please note that it is not possible to hand out a
cross reference list with all expected SKiiP currents. A relative
measurement and decision will always be much more
accurate, faster and less confusing.
All SKiiPs allow feeding 15Vdc into 24V. Modern SKiiP-III will take more
current at 15V due to lower input voltage. Elder SKiiP –II will go into under
voltage error and display this by the HB1 error LED. Those have an internal
shut down below 18V, the 24V supply is disabled.
12.) Turn the supply knob into position “15V into 24V” and observe error
LEDs and supply consumption.
Does your SKiiP only take 15Vdc supply (former versions of SKiiP)? Or does
your SKiiP use +/-15V supply (some special types)? Just supply accordingly
and monitor supply current in standby state.
Note
If your SKiiP is powered through the 15V supply please put
the knob [2] into the “monitor supply path 15V” position. There
is another, similar 100mOhm shunt and the voltmeter will
measure the voltage drop due to current consumption in the
15V path.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 9/16
8.
Status LEDs
13.) Monitor the ERROR LED indicators. Not all LEDs are relevant for all
types of SKiiP. A SKiiP GB has only one half bridge inside, thus the
status of the HB2 and HB3 LEDs must stay red.
Do all relevant LEDs turn green or stay red? In case of testing a SKiiP
GD all three HB errors should turn to green.
Check the temperature error LED status. A functional cold SKiiP must
show temp_error as green.
For fibre optical linked SKiiPs refer to the LED at the fibre optical input.
Green refers to “no error. “No light”, or “red light” are suspicious.
9.
Primary side 10kHz PWM current consumption
As mentioned above roughly 80% of faulty SKiiPs are identified by the
standby current consumption and status of error LEDs.
The SKiiP tester L23005 provides pulse patterns and steady ON commands
for a more detailed primary side examination. The chance to identify more
“hidden” problems will increase from roughly 80% to >85% by performing
the following additional functional tests of SKiiP Power Modules.
Supply the SKiiP to be tested in a convenient way and apply standby
condition. Start with the IGBT selection matrix switches [10] and [11] all in
upper positions (=default).
Note
For SKiiP GB only the HB1 switches are relevant, the SKiiP
interface of GB types does not use HB2 or HB3.
14.) Push the supply knob [6] and apply 10kHz of 50% duty cycle PWM
commands to all TOP IGBT switches inside the SKiiP. Monitor and
write down the current consumption.
15.) Push the supply knob [7] and apply 10kHz of 50% duty cycle PWM
commands to all BOT IGBT switches inside the SKiiP. Monitor and
write down the current consumption.
Note
Both values should be close together, one side tends to
always need a little more. The delta in current consumption
BOT=ON compared to TOP=ON is never identical; it always
shows a slight mismatch of a few mA.
16.) Push the supply knob [6] AND [7] simultaneously. Apply 10kHz of 50%
duty cycle alternating PWM commands to all IGBT switches inside the
SKiiP. Monitor and note down current consumption.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 10/16
Note
If your SKiiP does not tolerate 10kHz (part of self-protection of
some big modern SKiiPs) refer to the next test step, only. If
you insist on this measurement contact us to modify your
SKiiP tester to lower frequencies (e.g. 5kHz).
We refuse to generally do this change on all our testers,
because the signal ratio will decrease linear and a fast
identification needs time and more accuracy on the voltmeter.
10. Primary side steady ON current consumption
The last test procedure described above will only work on SKiiPs that
tolerate 10kHz. In addition it will deliver an indication of the average current
consumption. For a SKiiP with slacked joints a test procedure with steady
signals instead of PWM commands provides more stable fault identification.
To identify the exact position of the weak IGBT-driver channel use the knobs
[7] and [9] in combination with the position of the switching matrix [10], [11],
HB1,HB2, HB3. Always bring only one of the possible 6 IGBT channels into
a steady ON condition.
Allow a little settling time and write down the current consumption.
Note
Some SKiiPs GD have only one IGBT driver path broken. By
using the selection matrix you may identify the exact channel
and write it down. Compare the relative change in current
through all TOP and through all BOT switches. A notable
change in current consumption (e.g. from HB2 TOP to HB3
TOP) indicates a SKiiP problem.
11. Primary side analog signals
If the suspicious SKiiP passed all primary side tests so far return into
standby consumption. The position of knob [3] will give the output voltages
of the analog pins of the SKiiP interface.
17.) I_HB 1, HB2, HB3 will show the offset of the SKiiP internal current
sensor. It should be within several mV positive or negative.
Note
From our experience faulty current sensors deliver 25% to
50% of the maximum output rail as offset. This should lead to
much higher steady state amplitudes than +/- 50mV to locate
the fault. The steady state current consumption can already
identify, but not exactly locate the problem.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 11/16
Note
A SKiiP GB only connects I_HB1. Any measurements on HB2
or HB3 will just collect noise due to open end cables in the mV
range.
18.) The U_dc analog output should display zero with an offset of several
mVs. As your DC-link must be fully discharged due to safety
instructions, please double check the DC-link voltage (some SKiiPs
recharge even big capacitor banks due to Vce desaturation monitoring
up to 30Vdc).
19.) The Temp_analog signal gives the heatsink temperature according to
the SKiiP datasheet curve. At moderate (cold) temperatures most
SKiiPs display 0.3V …0.9V.
Note
If the SKiiP is still warm/hot from operation values up to
several volts can be monitored and the SKiiP is not weak
here. A broken sensor or a slack joint brings a voltage of
>8Vdc.
There are special types of SKiiP in the field that can
accurately measure & display very low temperatures. Please
refer to their characteristic curve in their datasheet.
12. Summary - Primary side monitoring
If the SKiiP under test has successfully passed all tests mentioned above
and is still considered to be faulty, it must be removed from the inverter to
check power terminal behaviour.
Note
From our experience we recommend to double check all other
components first. As mentioned, the chance that it is not this
SKiiP causing trouble is better than 85% after successful
passing all tests described above.
13. Secondary side monitoring - SKiiP as standalone unit
After the SKiiP has been removed from the application, access to the power
terminals for measurements is possible.
The SKiiP tester has a built-in, current-limited voltage source that provides
roughly 170Vdc with >100kOhm impedance. Decoupled from this high
voltage and connected in parallel is a 15V source limited to roughly 1.5A.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 12/16
This source provides power silicon measurements at higher voltage level as
well as forward voltage measurements of silicon devices in ON state at low
currents (1.5A).
Note
We are aware that 170V and 1.5 A do not test the limits of the
SKiiP silicon power capabilities. But from our experience a
damaged characteristic semiconductor curve can be detected
in most cases with this kind of source.
If the removed SKiiP arrives from the field as a standalone unit we
recommend performing the primary side tests in the new location.
Note
The SKiiP tester provides best results by comparing relative
readings.
Deciding the status of a SKiiP by its absolute readings always
needs the consideration of possible deviation from the test
setup. Deviation from test setups on site and in a in a repair
centre may occur from:
- different ambient temperature
- testing time (heating up of SKiiP circuit during measurement)
- power supply tolerance
- cable length and condition (supply voltage drop)
- shunt tolerance inside SKiiP tester
- voltage/current source tolerance inside SKiiP tester
- PWM frequency tolerance
- voltmeter calibration and accuracy
The SKiiP tester is designed as a lower cost device and
usually is profitable by reduced maintenance and shut down
time the first few usages.
We do not intend to narrow the tester-internal tolerances. This
would increase cost and still cannot provide much better
measurement accuracy, as some external test conditions still
can neither be considered, nor covered.
20.) Perform primary side measurements as described in the chapters
above.
21.) Fill out or complete the test protocol.
Note
Find a suggestion of a test protocol at the end of this
application note. Always prefer your company´s guidelines for
reports.
Consider that most faulty SKiiPs are returned to the supplier.
If your test protocol contains the relevant data that led to the
decision this device is faulty, you safe a lot of time & money at
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 13/16
the suppliers incoming inspection. So your company will
additionally benefit from this records.
22.) Turn the SKiiP supply knob [1] into OFF position.
23.) Attach the AC and DC cables to the first section of the SKiiP under
test. Some SKiiP testers need a cross tip screw driver, modern
editions use hand operated knurled screws. The orientation of the
cable-PCBs is failsafe.
24.) Turn knob [5] from “primary signal” into TOP position to monitor the
upper silicon of the attached halfbridge.
25.) Re-power the primary side of the SKiiP with knob [1] in standby state.
26.) Turn the knob [4] from “off” into “Vce(IGBT)”.
27.) Monitor the OFF state voltage drop of the TOP IGBT and its freewheeling diode in section one of the SKiiP. It should be around 170V,
not below 150V.If in doubt, compare to other sections of the same
SKiiP or to other SKiiPs.
28.) Push and hold button [7] with switch [10] in upper (=default) position.
Monitor and write down forward voltage drop of IGBT silicon at roughly
1.5A. It should read <600mV and be in the same range of all other
sections in ON mode.
29.) By releasing button [7] the readout must return to the 170V level.
30.) Turn knob [4] into Vf (diode) position.
31.) Monitor and note the forward voltage drop of the free-wheeling diode.
It should be in the same range as the ON state IGBT (<600mV) but
usually is different from the IGBT curve.
32.) Switch knob [4] into “off” postion.
33.) Switch knob [5] into position “BOT”.
34.) Repeat the measurements performed in position “TOP” now focusing
the BOT section.
35.) Write down the results.
Note
The use of the PWM generator knob [6] or [8] is not
recommended while testing power terminals. We do not
expect comparable results, the test setup starts to act as a
tiny buck or boost converter and the displayed values are not
stable. The use of PWM signals does not make sense here.
36.) Power down the SKiiP supply with knob [1] into “OFF” position.
37.) Remove AC and DC cables from the section that has been tested.
38.) Attach AC and DC cables to the next remaining section of the SKiiP
under test. 2-fold, 3-fold, or 4-fold SKiiPs need repetition accordingly.
39.) Repeat the measurements for TOP and BOT in steady ON and OFF
state of the IGBT.
40.) Repeat the forward voltage of the free-wheeling diode.
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 14/16
Note
As mentioned above some sections of some SKiiP types have
DC-link measurement installed. These sections bring out an
additional load [10 MegOhm range] to the tester´s internal
170V source. Double check for such types and consider such
section as non-faulty, even if the 170V voltage drops lower
than in the other sections of such SKiiP types.
For example a normal readout for a 3-fold Udc SKiiP can be:
open -HB1-HB2-HB3 : 172V-163V-150V-162V.
With DC-Link option on position HB2 this readout is not
suspicious. Without the DC-Link option HB2 it is suspicious.
14. Summary - Secondary side monitoring
If the SKiiP under test has successfully passed all tests – primary and
secondary side (=power terminals) there is a >95% chance that this SKiiP
does not have a problem and is worth to be tested/used in a high power
application.
Note
From our experience many SKiiPs are returned without having
internal trouble. This creates more down time because the
real reason for malfunction is not identified.
15. Additional hints - Calibration
For further details refer to the manual of the SKiiP tester.
Do only operate the unit in dry areas.
Intended usage:
- Saving time while troubleshooting in applications
- Decision assistant for „SKiiP is definitely faulty“ or „probably well“
- Test cycle time < 5min including test setup time
- No dismounting of SKiiP into subcomponents
- Less unsubstantiated rejects to Semikron
What is NOT covered?
- NO 100% substitute for inhouse Semikron functional test
- NO breakdown voltage measurement (only 170Vmax)
- NO gate leakage current measurement
- NO Rth-measurement,
- NO measurement with rated current (only 1,3A DC,max) , ...
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 15/16
Calibration
As the SKiiP tester is optimized for relative measurements the readouts of
the absolute values are less important. We do not recommend a scheduled
return to our company for calibration. In some countries shipping twice
exceeds the cost for a new tester.
A qualified operator can easily check the SKiiP tester for internal
malfunction:
- Mechanical damage (drop from wind turbine is a popular issue)
- Mechanically overstressed switches
- Current values not as expected from experience:
• Measure current consumption of SKiiP under test with a calibrated
meter
• Compare to the SKiiP tester´s readout.
• If readout is faulty, return for repair to replace the 100mOhm shunt.
- Voltage values Vce and Vf not as expected from experience:
• Measure 170V and no SKiiP attached with a calibrated meter (but
with the AC and DC cables mounted)
• Measure short circuit current in the 170V position (should be in the
range of 1.2 … 2A)
• If considered faulty, return for repair of the internal source.
- Broken power supply; replace with any 24V supply in the suitable range
- Overstressed cables; replace with LAN cable from any computer store
16. Service
Never carry out repair on your own, please contact:
Ing.-Büro M.Billmann
Lerchensteige 10
D-91448 Emskirchen
Phone:
+49-(0)9104-8235-88
Fax:
+49-(0)9104-8235-89
Email:
M.Billmann@ ib-billmann.de
L23005_SKiiP-Tester_Appnote_HTU_ENG_v1.1.doc; 19.05.2004; M.Billmann; 16/16