Selection Criteria for Thermometrics CL-Products

1.

by the acceptable life of the final products for which the thermistor becomes a component. The differential equation Pdt

rating of 80%, 100% load is calculated to be 125 watts. The maximum input current is calculated from the minimum

supply voltage. For a standard 120V supply, this could be rated as low at 110V. Therefore, input current would be

calculated by 125 watts/110 V = 1.14 Amps. Selection of the CL should have an I max rating of at least 1.14 Amps.

2.

The second step of selection of the CL is to understand the desired maximum inrush current allowable. This is generally

specificed by the components in line of the CL, such as the diode bridge. In the case of the diode bridge rated at 200 Amps,

one would should select a CL that would limit max surge current to 50% of the rating, therefore limit surge to a maximum

of 100 Amps. The listed maximum current flow is rated at 25°C, so derating is required if the ambient temperture is greater

than 25°C.

3.

The next selection of criteria for the CL is to understand the bulk Capacitance of the device to be protected. On power, the

bulk capacitance of the device appears as a short to the system. The designer needs to understand the bulk capacitance

at the RMS voltage rating of the system. Assuming the input capacitance is approximately 500 μFds, the selection of the

CL needs to be able to absorb input energy.

Using the above criteria, the selection of the CL provides multiple solutions. One would opt for the smallest size CL to achieve

the required protection. The selection criteria is as follows:

2. Max allowable Inrush current 100 Amps

3. Bulk Capacitance listed as 500 μfd

4. Choose smallest physical size that will allow protection for the device.

Criteria indicates that either the CL-150 or CL-160 would be suitable for the application. In the case of the CL-150 less heat is

dissipated allowing the operating resistance to drop but at a higher temperature. This increases efficiency of the system but

may lead to shorter component life.

AAS-920-325D-03/2014

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