The CWT Ultra mini (CWTUM) has the smallest cross section, clip-around, Rogowski coil on the market. Combined with its wide-bandwidth the CWT ultra mini is a versatile tool for many applications particularly power electronics development work.
Switching Waveforms in Power Electronic Circuits
The CWT ultra mini can be used for a wide variety of electronic measurements such as switching loss in power semiconductors, current sharing in parallel devices or checking that in-circuit inductance is not over stressing an IGBT or MOSFET.
The CWTUM is non-intrusive injecting only a few pH into the primary circuit, wide-bandwidth 30MHz, has a predictable known measurement delay, and is thin and clip-around making it easy to insert into even difficult to reach parts of the circuit.
The CWT ultra mini is small enough to measure the current in...
- Power device bond wires
- Load sharing in parallel TO-220 / TO-47 MOSFET devices
- Current distribution across a semiconductor wafer
- The connection between laminate power planes and IGBT MOSFET power modules
- Inductor and capacitor terminals in SMPS cct’s and power converters
...making it a very useful diagnostic tool as the density of power circuits increase!
Measuring Small AC Currents in the Presence of Large DC Currents (e.g. capacitor ripple)
Rogowski current transducers do not measure the DC component of a current. However unlike a CT or hall effect device they contain no magnetic materials so are unaffected by the DC current. Therefore it is possible to use a small, flexible, Rogowski coil to measure a small AC current in the presence of a large DC current whereas a sensor based on a magnetic principle would be expensive and bulky to prevent saturation effects. One such common application is measuring the ripple current in capacitors where the main current is DC or slow time varying.
Performance
| Peak current | 30A peak to 6kA peak |
| Output | ±6.0V peak |
| High Frequency Bandwidth (-3dB) | 30MHz |
| Low Frequency Bandwidth (-3dB) | Varies with model type (refer to datasheet) |
| Accuracy (typ.) | Calibrated to ±0.2% with conductor central in the Rogowski loop |
|
| Typical variation with conductor position ±2.0% of reading |
| Operating temperature range | 0℃ to +40℃ (Integrator electronics) |
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| –40℃ to +125℃ (Coil and cable) |
| Coil Lengths | 80mm (custom lengths available) |
| Coil thickness | 1.7mm max. |
| Peak coil insulation | 1.2kV peak |
| Cable Length (coil to integrator) | 1m (custom lengths available) |
| Power Supply | ‘B’ Battery 4 x AA (1.5V standard alkali batteries) ‘R’ Battery 4 x AA (1.2V NiMH batteries) |
