Itowa LS2 User manual

USER MANUAL
LOAD LIMITER
VA001001

USER MANUAL
LOAD
LIMITER
LS2
ITOWA
MALIMLS2GB
REV 0
07/07/15
Approved by the Engineering Manager: I. Martínez
ANY REPRODUCTION, EITHER COMPLETE OR IN PART, OF THIS MANUAL IS
STRICTLY PROHIBITED UNLESS ITOWA HAS GIVEN ITS WRITTEN CONSENT
OTHERWISE, ITOWA RESERVES THE RIGHT TO INITIATE ALL APPROPRIATE ACTIONS
AS ESTABLISHED IN LAW
ITOWA RESERVES THE RIGHT TO CHANGE THIS MANUAL WITHOUT PRIOR NOTICE.

LOAD LIMITER
USER MANUAL
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TABLE OF CONTENTS
1. INTRODUCTION 1-1
2. LS2 LOAD LIMITER OPERATING 2-1
2.1. OPERATING IN MODE ONE 2-1
2.2. OPERATING IN MODE TWO 2-2
3. ASSEMBLY OF LS2 LOAD LIMITER 3-1
3.1. CONNECTION OF CHARGING CELL 3-4
3.2. POWER SUPPLY 3-4
3.3. RELAY 1 CONNECTION 3-4
3.4. REALY 2 CONNECTION 3-4
4. LS2 LOAD LIMITER SETTING 4-1
5. RECYCLING 5-1
5.1. PACKAGING 5-1

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1. INTRODUCTION
LS2 is a high-precision and safety load limiter preventing accidents and protecting overload breakdowns in
overhead cranes and hoists.
It can also be applied to lifts, weight lifters, rope tensioning systems and in general to any system or
installation where a wire rope is subjected to traction and want to limit the maximum tension.
It improves precision and reliability of traditional alternative of motor load limitation.

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2. LS2 LOAD LIMITER OPERATING
The load limiter, by design, is intrinsically safe, that is, in case of failure or disconnection of the strain gauge
wire, it will stop all working operations. The limiter circuit have 2 relays able to cut a current of 16 A at
230Vac. These relays can be programmed, one of them works like a maximum load relay with 2 tripping-out
points: one instantaneously and the other delayed, that allows to adjust the instantaneous trip at 110% of
load and the delayed at 100% of load, the other relay works like a minimum load relay. Another way of
programming allows that both relays works as maximum load relays, with a programmable timer.
Hereinafter we will refer to the delayed time operation as mode TWO, and the maximum and minimum
mode as ONE. These two ways of programming are automatically selected depending on the connection or
disconnection values put on the relay TWO.
2.1. OPERATING IN MODE ONE
Operating in mode ONE allows to adjust the relay 1 as maximum load relay (with 2 tripping-points, one
instantaneously and other delayed), and the relay nº 2 as minimum load relay (snack cable detection).
When the load applied to the hoist exceeds one of the two programmed values, instantaneously or delayed,
the maximum load relay (point of disconnection of relay 1) will be deactivated immediately impeding the
lifting operation. This relay will be automatically reactivated when the load value falls below a previously set
value, this point will be called connection point of relay 1.
If the system has disconnected for exceeding the maximum instantaneous load, it connects when the load
falls below the disconnection value. If it has tripped for the delayed load value, it will be connected when it
falls below its respective value.
Normally, the value of time delayed disconnection relay 1 will be scheduled lower than programmed in
disconnection instant value. This operating allows you to prevent oscillations of the load produced by inertia
at the time of start lifting a mass whose value is close to the maximum load the limiter shoot.
The design of the timer of relay 1, allows that in case of a load swings above and below of the relay
disconnection point, it will not turn off until the applied load does not exceed the programmed value in relay
1, a time higher than the programmed in the timer.
NOTE: THE VALUE PROGRAMMED IN CONNECTION POINT MUST ALWAYS BE LOWER THAN
THE ONE PROGRAMMED IN THE DISCONNECTION POINT.

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When the load value drops below the programmed value in the relay 2 (point of disconnection of relay 2), it
will deactivate impeding the dropping operation. It will reactivate when the value of the load exceeds the set
value at the point of connection of the relay 2
NOTE: THE VALUE PROGRAMMED IN CONNECTION POINT MUST ALWAYS BE HIGHER
THAN THE ONE PROGRAMMED IN THE DISCONNECTION POINT.
2.2. OPERATING IN MODE TWO
Operating in mode TWO allows adjusting the relay 1 to operate identically as the mode ONE do, while relay
2 can be set as relay 1 but with a different tripping value and timing. This operating allows acting on the
second lift speed from a certain load permitting only activate the first speed.