How should the dial be set on an LR*D* overload relay?

Issue:
How to set the amperage on a TeSys D overload relay

Product Line:
IEC Overload Relays - GIC Product

Environment:
Global Product

Cause:
Installation

Resolution:
Per the instructions for the dial settings shipped with the device, the dial is representative of In (nominal current or FLA or the motor).  Depending on local codes and standards of the installation, this dial can be set within a range to remove cases of nuisance tripping while protecting the motor as well as accounting for service factor ratings.  The marking for "Trip amps are 125%" is based on the footnote "b" from the below table from IEC/UL 60947-4-1 and our testing during certification.

Below is the local code for NAM based installations as well as example calculations:

NEC 430.32 specifies motors shall be protected against overload and shall be selected to trip as follows:
• Motors with a service factor ≥ 1.15 => 125% maximum of motor nameplate full load ampere rating.
• Motors with temperature rises of ≤ 40 °C => 125% maximum of motor nameplate full load ampere rating.
• All other motors => 115% maximum of motor nameplate full load ampere rating.

If the above overload protection setting is not sufficient to start the motor or carry the load current then, the overload setting is permitted to not exceed the following:
• Motors with a service factor ≥ 1.15 => 140% maximum of motor nameplate full load ampere rating.
• Motors with temperature rises of ≤ 40 °C => 140% maximum of motor nameplate full load ampere rating.
• All other motors => 130% maximum of motor nameplate full load ampere rating.

Example 1: Motor nameplate with 10 Amp full load amp rating and Service Factor = 1.15.
NEC allows for overload tripping up to 125% of the rated nameplate motor current with a service factor of 1.15.   10 Amp x 125% = 12.5 Amps, set overload trip dial to 12.5 Amps maximum.

Example 2: Motor nameplate with 10 Amp full load amp rating and Service Factor = 1.0.
NEC allows for overload tripping up to 115% of the rated nameplate motor current with a service factor of less than 1.15.   10 Amp x 115% = 11.5 Amps, set overload trip dial to 11.5 Amps maximum.

게시 대상: 슈나이더 일렉트릭 Korea