Topics

• Hall Effect
• K-Factor
• Impulse Test
• High Current
• Radio Frequencies
• Shielding and Filtering

• Hall Effect “noise” is generated when magnetic materials are in a magnetic field and a current passes through the magnetic material simultaneously.
• Cimco's position: Hall-Effect noise, as related to temperature measurement errors, is negligible with Type E Thermocouples.
• Do not use Type K Thermocouples.

• Harmonics are generated by distortions in current or voltage wave-forms.
• These harmonics increase Hall Effect noise and temperature in transformer windings.
• Cimco's Position: K-Factor harmonics do not influence the accuracy of Type E.
• Thermocouples and the instrument will indicate actual temperature of the windings.

• K-Factor and Hall Effect noise are very high during impulse test and can create a false high temperature signal which could cause the trip relay to change state and "trip" the transformer.
• Cimco instruments, with Cimco's Type E thermocouples, will operate properly during impulse test.
• Actual tests were conducted.
• Contact Cimco Electronics, Inc. at cimco@cimcoelectronics.com for advice with electrical insulation on the thermocouples.

• Hall-Effects and Eddy-Losses increase as winding currents increase.
• Winding temperature will increase with increased losses caused by Hall-Effects and Eddy-Losses.
• Hall-Effect and Eddy Current influences on temperature are accurately sensed by the Type E thermocouples and displayed on Cimco's control panel.

• Radio frequencies can induce noise, which become signals, into sensors containing magnetic materials.
• False trip signals can de-energize the transformer.
• Noise signals from radio frequencies do not influence Cimco's instrument.
• Low-quality insulation on input power leads can cause malfunctions on electronic equipment.
• Actual tests were conducted.

• Well designed transformer coil shielding can limit noise to manageable levels.
• VERY HIGH COST!
• Shielding can create unexpected problems.
• Use shielded sensors with caution.
• Sensor leads in steel conduit are acceptable.
• Cimco offers "special" insulated thermocouples for unusual noise and voltage applications.
• Signal inputs are filtered to 75 dB.
• Model A21 uses two carbon steel boxes for very high-level protection against magnetic and high voltage fields.