BR 230/400-10...400
7
7.
Functional description (see connection diagram)
After switching on the operating voltage on L1 and L2 the main contactor interlock (terminal
X5,X6) closes. The motor can be started.
A starting logic makes sure that braking is not yet initiated when the plant is switched on with the
master switch while the motor is still switched off.
The fully automatic run of the braking interval starts with the switch-off of the motor contactor
which at the same time closes the contact (terminal X3,X4). During braking the main contactor is
interlocked via the contact (terminal X5,X6). After a delay time in which the remanent voltage of
the motor decays to a value that is harmless for the power semiconductors (0.25sec. for small-
size braking devices, up to 1.5sec. for the 400A-version), the braking contactor pulls in. After-
wards an adjustable d.c. voltage is applied to the motor winding. The resulting magnetic field has
a braking effect on the still rotating rotor. The d.c. voltage is generated by a thyristor generalized
phase control. Special circuits protect the power semiconductors against overvoltage. With the
potentiometer "I" the braking torque can be adjusted in wide ranges. Experience shows that a
braking current amounting to double rated motor current has a good braking effect. When
commissioning the device, the braking current, for safety reasons, has to be checked with a
moving-iron instrument. Multimeters and clamp-on probes give wrong measurements and must
not be used for this purpose. Value-adjustments higher than the rated device current are not
allowed. If, due to heavy rotating masses to be slowed down, the braking time at rated device
current is still too long, the next larger braking device has to be used.
With the potentiometer "t" the braking time can be adjusted from 2 to 14sec.. At the end of the
adjusted braking time the braking voltage is switched off and the braking contactor drops out with
delay. Thereupon the contact (terminal X5,X6) recloses, so that the motor can be started anew.
Warning note :
When putting the device into operation for the first time, the braking current
should be checked with a true r.m.s. measuring instrument. Clamp-on
probes or digital multimeters may only be used if they can measure the true
r.m.s..
Note:
If the braking time at rated device current is too short, due to the fact that the
centrifugal masses to be slowed down are too large, a device featuring a
higher rated current has to be used.
7.1
LED indicators
LED – green
mains voltage is applied, braking device is ready
LED – red
braking current flows
