Application planning
6.6 Use in the motor protection area
3VL molded-case circuit breakers
74
System Manual, 03/2009, 110 0110 - 02 DS 01
6.6
Use in the motor protection area
The overload and short-circuit releases are designed for optimal protection and direct-
starting three-phase AC squirrel-cage motors. The motor protection circuit breakers are
sensitive for phase failures and have an adjustable trip class.
The overcurrent trip units operate with a microprocessor.
Operating principle of the overcurrent trip units
The tripping characteristic curves of the current-dependent delayed overload releases are
specially designed for overload protection of 3-phase AC motors.
In the case of the current-dependent delayed overload release "L", the value I
R
can be set to
be 0.4 to 1.0 times the rated current I
n
of the circuit breaker. This occurs in 0.01 increments
(e.g. 0.40 / 0.41 / 0.42 to 0.99 / 1.0 x I
n
), so that the circuit breaker exactly matches the
nominal current of the motor to provide optimal protection.
The current converters in the SENTRON VL circuit breaker don't only measure the load
current, they also supply power to the electronic overcurrent trip unit.
This independence from an external energy supply guarantees a high standard of safety.
Area of application
Machine tools, manufacturing systems, presses, fans, air-conditioning units and packaging
machines all require motors that must be protected. This is the main area of application of
the SENTRON VL circuit breakers for motor protection.
Trip class
The SENTRON VL circuit breakers offer the option of selecting from various trip units with
fixed or adjustable trip classes that are suitable for differing motor applications.
ETU 10 M
This version is equipped with a thermal memory, phase failure sensitivity and the fixed trip
class 10.
ETU 30 M
This version is equipped with an adjustable trip class of 10A to bis 30 in addition to the
thermal memory and phase failure sensitivity.
ETU 40 M
This version enables the parameters and the trip class to be configured step by step using a
menu on the LCD display that is built into the trip unit.
Содержание SENTRON 3VL series
Страница 2: ......
Страница 10: ...Table of contents 3VL molded case circuit breakers 10 System Manual 03 2009 110 0110 02 DS 01 ...
Страница 40: ...System overview 4 2 Key data 3VL molded case circuit breakers 40 System Manual 03 2009 110 0110 02 DS 01 ...
Страница 350: ...Correction sheet 3VL molded case circuit breakers 350 System Manual 03 2009 110 0110 02 DS 01 ...
Страница 358: ...Glossary 3VL molded case circuit breakers 358 System Manual 03 2009 110 0110 02 DS 01 ...
Страница 359: ......