12
LH 5946 / 130910 / 363
Motors with switched windings
(e.g. star delta starters, reversing circuits, multi speed motors)
With these applications please make sure, that the measuring inputs must
be linked via the motor windings. An open connection will result in broken
wire indication and disable the safety contacts.
When connecting the LH 5946 to a 3-phase motor with star delta starter
the star contactor must be energized while the motor is switched off, in
order to achieve closed circuits between L1-L2-L3 via the motor windings.
If it is not possible to switch in the star contactor after the motor is swit-
ched off, the measuring inputs of the LH 5946 have to be connected
like a single phase connection. L2-L3 are bridged and connected to one
end of a motor winding and L1 to the other end of the same winding.
For reversing circuits and multi speed motors please follow the same
procedure.
If in a 3-phase connection of LH 5946 windings are switched over, and the
interruptions of the measuring circuits are longer then 2 s, the standstill
monitor detects broken wire. In order not to store this failure, the unit should
work with auto reset.
Operation with DC motors
The LH 5946 can be used on DC motors if these generate a remanence
voltage during run down.
The connection is made similar as with a single phase motor.
As the remanence voltage in this case is normally a DC voltage the unit will
detect a broken wire / offset failure and indicate it on LED „ERR“ and semi-
conductor output „ERR“. Taking this in mind and operating the unit with auto
reset for these failures the unit can be used for safety standstill monitoring.
Operation with electronic motor controller
(inverters, DC-brakes)
The operation of LH 5946 to detect standstill on motors with electronic
motor control is possible, if the output voltage of the motor controller drops
under the adjusted response value on standstill. (No position control on
inverters, no DC voltage on brakes after standstill).
If the inverter produces a DC offset or a DC brake is active, an offset or
broken wire failure is indicated on LED „ERR“ and semiconductor output
„ERR“. This error resets automatically if on terminals X2-X3 automatic
reset is selected.
When there are inverters in the installation it is recommended to use screened
measuring wires to the motor. The screen can be connected to the motor.
Attention
If the motor current is run down by inverters or softstop modules in a
slow way the motor may be de-magnetised. It is necessary to check if
the remaining remanence voltage is sufficient to guarantee a correct
and safe standstill monitoring. At high frequencies an increasing
damping of the measuring inputs has to be taken into account (see
page 13, technical data measuring input „response value dependant
on frequency“).
Operation notes
Preparation
•
Motor on standstill
•
Terminals L1-L2-L3 connected to the motor windings
•
Provide link on terminals X1-X2
•
Provide also link on X2-X3 on DC motors or DC braking
•
Adjust U
an
to minimum
•
Adjust t
s
to minimum (0.2 s)
Connect correct auxiliary voltage to terminals A1-A2
⇒
After 1 sec the LEDs „UH“ and „OUT“ light up green and the safety
contacts are switched on. Also the monitoring relay and the semiconductor
output „ON“ must be activated.
If standstill is not detected (LED „OUT“ lights yellow), possibly interfe-
rence is coupled on the measuring circuit. Adjust U
an
higher or screen the
measuring wires.
Start of motor
⇒
LED „OUT“ changes colour to yellow. The output relays and the
semiconductor output „ON“ switch off. On DC motors the LED „ERR“ starts
to flash after 2 s with flash code 2 and the output „ERR“ comes on.
Stop of motor – run down DC braking off
The speed at which standstill is detected (yellow LED „OUT“ changes to
green/green flashing) can be adjusted on Potentiometer „U
an
“. When the
run down is slow or irregular the time delay must possibly be increased
to avoid switching on and off of the output relays. Possibly this effect can
also be avoided by slightly increasing Uan. During time delay ts the LED
„OUT“ flashes green.
If standstill detection shall only take place at very low speed of the motor,
U
an
is set normally to minimum. By increasing the delay time ts a possible
pulsing of the output relays can be avoided. A longer time delay will also
guarantee standstill detection only when the motor has already stopped
turning. (especially on motors that generate only a small remanence voltage).
On slow decrease of motor speed it is possible that a simultaneity failure
occurs (see failure monitoring) when the measuring channels reach the
tripping values slowly and not within 2.5 sec. To avoid this failure a single
phase connection could be the solution (to make sure that both inputs get
the same signal) or the increase of the setting value U
an
.
If the run down time of the motor is short ts can be set to a minimum (0.2
s). This is suitable in production systems to shorten machine cycles.
Attention
It is the responsibility of the user to adjust Uan and ts in a way
that standstill detection and enabling of the safety contacts in the
application is only possible when danger to men and material by
the rotating can be excluded.
Setup and setting
