PEM CWT Mini User manual

Powe
r
Electronic
Measurements
ROGOWSKI
CURRENT
WAVEFORM
TRANSDUCERS
INSTRUCTIONS
FOR
USE
CWT
Mini/MiniHF
POWER
ELECTRONIC
MEASUREMENTS
Ltd.
Tel:
+44
115
946
9657 •
Fax:
+44
115
946
8515
Email:
[e-mail] •
Web:
www.pemuk.com
www.pemuk.com
Nov
2017
(주)바이텍
www.buytek.co.kr
Mail : [email protected].kr
Tel : [phone]
ax : 043) 267-9601F

INTRODUCTION ............................................................................................. 3
TECHNICAL SPECIFICATION ........................................................................ 3
STANDARDS AND APPROVALS .................................................................. 5
OVERVIEW: CWT MINI/MINIHF ................................................................. 6
HANDLING INSTRUCTIONS ......................................................................... 7
SAFETY AND PRE-USE CHECKS ................................................................... 8
POWER OPTIONS ........................................................................................... 9
REPLACING THE BATTERY ............................................................................ 9
SWITCHING ON ............................................................................................ 10
OBTAINING THE BEST MEASUREMENT ................................................. 11
CLEANING AND DECONTAMINATION ................................................... 12
WARRANTY .................................................................................................... 12
RETURNING YOUR CWT FOR RECALIBRATION OR REPAIR ............. 12
2
Nov 2017
INTRODUCTION
The CWT Mini/MiniHF (CWT) Rogowski Current Waveform Transducer from PEM combines
high bandwidth performance with minimal disruption to the circuit under test. These
instructions must be followed whenever the unit is used. They are intended to help you
obtain the best and safest performance from the transducer.
Throughout these instructions there are a number of warnings which must be observed to
ensure safe operation of this unit. These warnings are identified by the following symbol:
A
The intended use is for the measurement of AC current. PEM accepts no responsibility for
any damage resulting from careless use, or failure to observe these instructions.
TECHNICAL SPECIFICATION
Peak Current Refer to ID Label
Peak Output Voltage
±6V (corresponding to ±Peak Current Rating)
Output Cable
0.5m BNC to BNC 50Q cable
In order to maintain safety, the BNC terminal must be connected to
equipment that is separated from hazardous voltages by at least
double insulation.
Output Load
> 100kQ (for rated accuracy - recommend DC1MQ on scope)
= 50Q (CWT can drive a 50Q load if necessary)
NB. A load of 50Q will reduce the CWT sensitivity by half its normal
value and limit the peak output voltage to ±2V.
Bandwidth (-3dB)
Refer to the datasheet
Operating Temp. Range
0°C to +40°C (Integrator electronics)
-40°C to +1 00°C (Mini Coil and cable)
-40°C to +125°C (MiniHF Coil and cable)
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Nov 2017

Accuracy (typ.)
(5% to 100% Peak Current)
Calibration
Nominally ±0.2% with the conductor central in the Rogowski loop.
See the calibration certificate for further details.
Positional Accuracy
±2% variation of accuracy with conductor position in the loop
(see 'Obtaining The Best Measurement')
Linearity
±0.05% of reading
Noise (Max)
Refer to datasheet
Coil Insulation
5kV peak (Black or Yellow Coils)
2kV peak (Green Coils)
Coil Bend Radius
14mm
Absolute di/dt Ratings
MiniHF 100kA/pis (peak) 11.2kA/pis (rms)
Mini 40kA/pis (peak) | 1 .OkA/pis (rms)
Environmental
Indoor use / Altitude up to 2000m
Installation Category III, Pollution Degree 2.
Max. Rel. Humidity: 80% up to 31 °C
Decreasing Linearly to 50% at 40°C
Overvoltage Transient Cat III 600V
Operation with External Adaptor
DC Supply Voltage 12Vdc (+/-10%)
DC Quiescent Current
60mA @12VDC - 'B ’ version standard alkali battery supplied CWT
130mA @ 12VDC - ‘ R ’ version NiMH Rechargeable battery CWT
DC Socket Type 1
.3mm Jack Socket - Centre Positive Tip
The unit should only be powered by the supplied mains adaptor.
Adaptor Supply Voltage 100-240VAC
Adaptor Supply Frequency
50 - 60Hz
Adaptor Supply Current
450mA Max @ 1 00VAC Input
Supply Voltage Fluctuation up to 10%
Operation with Battery
*B ’ version: 4x1 .5V AA alkaline
Battery Life: 25hrs typ.
Battery Supply
‘ R ’ version: 4 x 1.2V NiMH rechargeable batteries
Battery Life: 10hrs typ. (based on a 1400mAh cell)
Typical Recharge Time: 40 hrs
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Nov 2017
STANDARDS AND APPROVALS
EMC Approvals
EN61 326-1:2013
FCC Title 47 (CFR:2010, Part 15b)
Safety Approvals
EN61010-1:2010
EN61 010-2-032:2012
Quality System
IS09001:2015
C C { roh . s 1
노 I Compliant I
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Nov 2017

OVERVIEW: CWT MINI/MINIHF
1. Rogowski Coil (Probe)
2.
Probe Tree End 1
3. Ferrule
4.
Connecting Cable
5. DC Power Socket
6. DC Power Status LED
7.
Enclosure
8.
BNC Output Socket
9.
4 x AA batteries
10. Status Indicator LED
GREEN = ON
RED = Battery LOW
11. Power Button
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Nov 2017
HANDLING INSTRUCTIONS
To achieve such an extremely thin Rogowski coil the CWT Mini/MiniHF is necessarily delicate.
Every effort has been made to ensure that the CWT Mini/MiniHF is as robust as possible. To prolong
the life of the coil please observe the following handling instructions.
Releasing The Coil
The free end of the coil is
unclipped by applying gentle
pressure in the direction shown.
OPEN IN THIS
DIRECTION
Correct Coil Insertion
The coil is correctly positioned when the free
end of the coil is fully inserted into the ferrule.
When correctly inserted, the ferrule will grip
the coil and hold it securely.
Never force the free end of the coil into the ferrule.
This may damage the coil insulation.
Take care not to put any force onto the cable attached to the coil.
This may damage the coil.
When not in use return the CWT coil to its protective case.
The minimum bend radius of this coil is 14mm. This is the minimum radius that the coil
can be bent without risk of damaging the coil or shortening its life.
A
A
A
A
7
Nov 2017

SA FETY AND PRE-USE CHECKS
®
The CWT does not provide protection of the user from electric shock whilst
applying or removing the probe from HAZARDOUS LIVE conductors.
Additional protective means are necessary to avoid electric shock from
HAZARDOUS LIVE conductors which cannot be de-energised.
If HAZARDOUS LIVE voltages are present and accessible in the
installation appropriate protective equipment must be used.
The Rogowski coil must not be used if the coil is damaged or the probe
wear indicator is visible. The wear indicator is a layer of contrasting colour
under the outer surface of the coil.
If the CWT is used in a manner not specified by the manufacturer the
protection provided by the equipment may be impaired.
THE CWT MINI/MINIHF ROGOWSKI COIL
/分 、 The integrity of the insulation around the Rogowski coil itself must be VISUALLY
/•\ INSPECTED before use, and the unit must NOT BE USED if there are signs of
damage.
When bending the flexible coil around a conductor, avoid tight bends and sharp edges
/ 卜 、 that could damage the coil.
A
The voltage rating (safe PEAK working voltage) is clearly labelled on the coil. For the
CWT Mini this is either 2kV peak or 5kV peak. Never use at voltages greater than this
value.
A
Voltage ratings are only valid if the 'free-end* of the coil is fully inserted into the socket,
and remains fully inserted during use. The coil has a friction fit, the coil is fully inserted
when the user feels they can ease the coil free end into the ferrule no further.
A
The voltage ratings are appropriate for intermittent use of the CWT as a test
instrument and not for continuous use in a permanent installation.
The ratings are derived from the following standard test: Coils rated for 2kV peak are
flash tested for one minute at 3.8kVrms using a 50Hz sine-wave voltage - those rated
for 5kV peak are tested at 8kVrms.
For permanent installation the coil should be situated such that corona, which will
eventually damage the coil insulation, cannot occur. For information regarding
permanent installation of PEM's Rogowski coils on high voltage equipment please
consult PEM.
A The user must ensure that the absolute maximum rated di/dt is not exceeded
THE INTEGRATOR
/分 、 The CWT must only be used with oscilloscopes or monitoring equipment which have
their BNC INPUTS PROPERLY GROUNDED.
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Nov 2017
POWER OPTIONS
The CWT can be powered by an external DC source or by one of two battery options. The
battery option is displayed along with the model type on the unit serial number label and will
state either standard non-rechargeable batteries [B] or rechargeable option [R]
External Supply
The CWT can be powered by an external DC supply. The DC voltage must be 12V(±10%)
using a suitably sized, centre positive connector. When the DC supply is present a RED
indicating LED adjacent to the socket is illuminated.
Standard Alkaline Batteries
Four fully charged AA alkaline batteries provide approx. 25 hours operation. Healthy
batteries are indicated by the GREEN LED. If the LED is RED the batteries are depleted and
must be replaced.
When the DC voltage is present the batteries are inoperative.
Rechargeable Batteries
Four fully charged rechargeable AA cells provide approx. 10 hours operation. Healthy
batteries are indicated by the GREEN LED. If the LED is RED the batteries are depleted and
must be replaced or recharged.
When the DC supply is present the batteries are inoperative and the external DC voltage
powers the transducer. In addition, when the DC supply is present (regardless of whether the
transducer is ON or OFF) the rechargeable batteries are trickle-charged.
REPLACING THE BATTERY
Low battery is indicated by a red LED located near the power switch. To replace the battery,
switch off the unit, remove the battery cover and replace with appropriate batteries for your
unit type.
It is recommended that the circuit under test is de-energised or the probe is removed from
the test circuit before replacing the batteries.
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Nov 2017

SWITCHING ON
f 分 、 Before installing the CWT and taking a measurement refer to SAFETY AND
PRE-USE CHECKS and HANDLING INSTRUCTIONS to ensure safe
operation of your CWT.
卜 、 Your CWT must only be used with oscilloscopes or monitoring equipment
which have their BNC inputs properly grounded.
1. Connect the BNC output of the transducer to your grounded oscilloscope or current
monitoring equipment.
2. Having carried out the VISUAL INSPECTION of the Rogowski coil, unclip the coil and
wrap it around the de-energised conductor under test.
3. Insert the free end of the coil fully inside the ferrule.
4. Re-energise the conductor.
5. Use the push-button to switch ON by pressing and releasing the button, and to turn OFF
by depressing the button fully; the LED indicates that the transducer is ON when the LED
is GREEN.
6. After switch on the CWT may require a settling period of up to 2 minutes before providing
an accurate measurement. The settling period is dependent on warm-up time and the low
frequency bandwidth.
10
Nov 2017
OBTAINING THE BEST MEASUREMENT
The Rogowski coil should be positioned so that the conductor under test is encircled by the
coil but is not adjacent to the cable attachment (see picture below). Arrows near the ferrule
indicate the direction a positive current should flow through the coil loop in order to obtain a
positive output voltage. The CWT has been calibrated with the conductor near the centre
(position A), and this is the ideal position for accuracy.
For the best high frequency performance, the centre of the current should lie on the line
shown A to B, where B is half way around the circumference of the coil.
SENSITIVITY TO EXTERNAL CURRENTS AND VOLTAGES
The sensitivity of the CWT to currents that are outside the closed loop of the Rogowski coil is
very small, provided that the external currents are less than the current rating of the unit or
that such currents are relatively distant from the coil. In the vicinity of a multi-turn conductor
the effects are far stronger than from a single conductor carrying the same current, and such
positions should be avoided.
If there is a surface with a high voltage very close to the coil and the voltage is subject to
high rates of change (e.g. 1 kV/ps) or high frequency oscillations in the MHz range, then
measurement error can arise due to capacitive coupling to the coil. However in the case of
the CWTMiniHF the Rogowski coil is fitted with an electrostatic screen underneath the coil
insulation. This provides excellent immunity to fast transient voltages and greatly attenuates
any electrostatic interference.
To check for any unwanted response to adjacent fields, it is recommended to quantify the
output of the CWT when close to (but not encircling) the conductor under test. This will reveal
the magnitude of any unwanted responses to currents close to, but outside, the coil.
OUTPUT CABLES
Your CWT has been supplied with a 500mm BNC to BNC output. It is possible to use longer
cables and these should be of a 50ohm single screened co-axial cable type.
PEM does not consider the use of extension cables to be problematic from the noise
viewpoint but consideration should be given to the routing of very long cables.
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Nov 2017

CLEANING AND DECONTAMINATION
To prevent surface contamination the Rogowski coil and cable should be inspected regularly.
To clean the coil and cable use a mild detergent and water to remove any contamination,
wipe with clean water to remove the detergent and dry thoroughly with a clean cloth. The
CWT must be disconnected from any external circuit and turned OFF prior to cleaning.
PEM accepts no responsibility for the use of any other cleaning solvents or cleaning
methods.
WARRANTY
The coil is guaranteed to be free from defects due to materials and workmanship for 12
months and the integrator for 24 months from the date of despatch from Power Electronic
Measurements Ltd.
In the event of a defect where the transducer has not been misused the CWT should be
returned to PEM with all freight charges to be paid by the customer. Correction shall be in the
form of repair or replacement.
RETURNING YOUR CWT FOR RECALIBRATION OR REPAIR
To return the CWT to PEM for repair or recalibration please contact PEM in advance for
shipping instructions (refer to www.pemuk.com for contact details and our returns
procedure).
PEM shall not be liable for any consequential damages, losses, costs or expenses arising
from the use or misuse of this product however caused.
For technical updates and the latest product releases please consult
POWER ELECTRONIC MEASUREMENTS Ltd.
Gloucester House, Wellington Street, Long Eaton, Nottingham, NG10 4HS, U.K.
Tel: [phone] • Fax: [phone]
Email: [e-mail] • Web: www.pemuk.com
12
Nov 2017