FLC (Full Load Current) Settings - TeSys T User Guides

FLC Definition

The Full Load Current (FLC) represents the actual full-load current of the motor being protected by the LTMR controller. The FLC is a motor characteristic and can be found on the motor plate.

Many protection parameters are set as a multiple of FLC.

The FLC can be set from FLCmin to FLCmax.

Examples of FLC settings are detailed below.

Other Definitions

Load CT ratio = Load CT primary / (Load CT secondary * Passes)

Current sensor max = Current range max * Load CT ratio

Current range max is determined by the LTMR controller commercial reference. It is stored in units of 0.1 A and has one of the following values: 8.0, 27.0, or 100.0 A.

Contactor rating is stored in units of 0.1 A and is set by the user between 1.0 and 1000.0 A.

FLCmax is defined as the lower of the Current sensor max and the Contactor rating values.

FLCmin = Current sensor max / 20 (rounded to the nearest 0.01 A.). FLCmin is stored internally in units of 0.01 A.

NOTE:

The modification of the Contactor rating and/or Load CT ratio modifies the value of the FLC.
Do not set the FLC below the FLCmin.

Conversion of Amperes to FLC Settings

FLC values are stored as a percentage of FLCmax

FLC (in %) = FLC (in A) / FLCmax

NOTE: FLC values must be expressed as a percentage of FLCmax (resolution of 1 %). If you enter an unauthorized value, the LTMR will round it up to the nearest authorized value. For example, on a 0.4-8 A unit, the step between FLCs is 0.08 A. If you try to set an FLC of 0.43 A, the LTMR will round it up to 0.4 A.

Example 1 (No External CTs)

Data:

FLC (in A) = 0.43 A
Current range max = 8.0 A
Load CT primary = 1
Load CT secondary = 1
Passes = 1
Contactor rating = 810.0 A

Calculated parameters with one pass:

Load CT ratio = Load CT primary / (Load CT secondary * passes) = 1 / (1 * 1) = 1.0
Current sensor max = Current range max * Load CT ratio = 8.0 * 1.0 = 8.0 A
FLCmax = min (Current sensor max, Contactor rating) = min (8.0, 810.0) = 8.0 A
FLCmin = Current sensor max / 20 = 8.0 / 20 = 0.40 A
FLC (in %) = FLC (in A) / FLCmax = 0.43 / 8.0 = 5 %

Example 2 (No External CTs, Multiple Passes)

Data:

FLC (in A) = 0.43 A
Current range max = 8.0 A
Load CT primary = 1
Load CT secondary = 1
Passes = 5
Contactor rating = 810.0 A

Calculated parameters with five passes:

Load CT ratio = Load CT primary / (Load CT secondary * passes) = 1 / (1 * 5) = 0.2
Current sensor max = Current range max * Load CT ratio = 8.0 * 0.2 = 1.6 A
FLCmax = min (Current sensor max, Contactor rating) = min (1.6, 810.0) = 1.6 A
FLCmin = Current sensor max / 20 = 1.6 / 20 = 0.08 A
FLC (in %) = FLC (in A) / FLCmax = 0.43 / 1.6 = 27 %

Example 3 (External CTs, Reduced Contactor Rating)

Data:

FLC (in A) = 135 A
Current range max = 8.0 A
Load CT primary = 200
Load CT secondary = 1
Passes = 1
Contactor rating = 150.0 A

Calculated parameters with one pass:

Load CT ratio = Load CT primary / (Load CT secondary * passes) = 200 / (1 * 1) = 200.0
Current sensor max = Current range max * Load CT ratio = 8.0 * 200.0 = 1600.0 A
FLCmax = min (Current sensor max, Contactor rating) = min (1600.0, 150.0) = 150.0 A
FLCmin = Current sensor max / 20 = 1600.0 / 20 = 80.0 A
FLC (in %) = FLC (in A) / FLCmax = 135 / 150.0 = 90 %