Technical information

The thermal protection is required f or all the motors r egardless of the size, unless

the motor is marked and authorised as self protected (impedance of the windings

is sufficient to prevent overloads).

Thermal relays, fuses, all the overload relays are admitted as protection from the

overload.

The power converters e.g. the reverse devices can perform this function only if

explicitly indicated in the instructions and only if the related instructions comply

with to the letter: some converters check the overload internally make checking

the through energy (I

t), other converters require the use of thermostats or

thermocouples. Failure to comply with the instructions will mean the protection

function is nullified.

The motors can have integrated protection providing that the assembly is certified

in all its parts: the use of self-protected must be shown in the schematics.

The maximum protection calibr

ation m ust not e xceed 115% of the r ated curr ent on

the plate. In the case of slow intervention, on start up or during normal

functioning, the protection can be increased up to 130%: in the case of components

that can be regulated the correct calibration must be indicated on the schematics.

In the case of thermal relays with resistors that can be replaced (NEMA

construction relays) the proper calibration must be shown on the schematics and

the catalogue code of the element be replaced must be attached.

EXAMPLE

In the example the plate current

is suggested and if it is unknown

FLA figures are used.

The calibration must not be

greater than 7.6 A x 1.15 = 8.7 A

If an overload relays with an

adjustable threshold is used the

device 140M-C2E-C10 with

adjustability range between

6.3 A and 10 A will be selected.

If a IEC/UL/CSA thermal relays

is used the choice will fall on

the 193-ED1DB (electronic)

with regulation range between

3.2 and 16 A.

At the moment of installation

the overload relays and

electronic O/L relays must be

adjusted at 100% of motor FLA.

BRANCH CIRCUIT

(*) Effective March 1, 2007 internal wiring < 14 AWG is only permitted in

industrial machinery panels, and must be protected by a device marked

suitable for connection and protection of that gauge of wire.

(*)