TM-DC Thermal-Magnetic Trip Unit for 3P and 4P Circuit Breakers from 250 A to 600 A

Introduction

The TM-DC thermal-magnetic trip unit for 3P/4P circuit breakers from 250 A to 600 A are built-in trip units.

They are designed for DC general-purpose applications.

The TM-DC 3P/4P trip units provide:

• adjustable thermal threshold

• adjustable magnetic pick-up

Description

The setting range and adjustment dials are on the front of the trip unit.

A Setting range for TM-DC thermal-magnetic 3P/4P trip unit

B Adjustment dial for the thermal protection pick-up Ir

C Adjustment dial for the magnetic protection pick-up Ii

Setting the Thermal Protection

The thermal protection pick-up Ir is set by a 5-setting dial.

Turning the thermal protection adjustment dial (A) modifies the trip curve as shown (B).

The following table shows the values of the pick-up Ir (in amperes) for thermal protection (values indicated on the dial) with respect to every trip unit rating, relative to the position of the dial Ir.

Trip Unit Rating In (A) at 40 °C (104 °F)
250	320	400	500	600
Pick-up Ir (A) at 40 °C (104 °F)
175	224	280	350	420
200	256	320	400	480
225	288	360	450	540
250	320	400	500	600

Setting the Magnetic Protection

The magnetic protection pick-up cannot be adjusted and equals the value shown below: