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Safety
Rating
Mechanical
Information
Data
Installation
10.5 DC brake with external zero speed sensor
For loads which may vary between braking cycles, there are benefits in using an external zero-speed sensor to interface with the
Digistart IS for brake shut-off. This control method ensures that the Digistart IS braking will always shut off when the motor has
reached a standstill, thus avoiding unnecessary motor heating.
The following schematic diagram shows how you can use a zero-speed sensor with the Digistart IS to turn the brake function off at
motor standstill. The zero-speed sensor (A2) is often referred to as an under-speed detector. Its internal contact is open at
zero-speed and closed at any speed above zero-speed. Once the motor has reached a standstill, the Digistart IS will go into
Emergency Stop mode and remain in this state until the next start command is given (i.e. next application of KA1).
The Digistart IS must be operated in remote mode and Pr 3A Input A Function must be set to emergency stop.
If the brake torque is set too high, the motor will stop before the end of the brake time and the motor will suffer
unnecessary heating which could result in damage. Careful configuration is required to ensure safe operation of the
starter and motor.
CAUTION
A high brake torque setting can result in peak currents up to motor DOL being drawn while the motor is stopping. Ensure
protection fuses installed in the motor branch circuit are selected appropriately.
Brake operation causes the motor to heat faster than the rate calculated by the motor thermal model. If you are using
brake, install a motor thermistor or allow sufficient restart delay (Pr 6G).
CAUTION
Figure 10-5 DC brake with external zero speed sensor
1/L1
3/L2
5/L3
1/L1
3/L2
5/L3
E
2/T1
4/T2 6/T3
M3
Control voltage
1
Motor terminals
2
Three-phase supply
3
Emergency stop mode (shown on starter display)
4
Start signal
5
For details on configuring DC Brake, see Brake on page 41.
When using DC brake, the mains supply must be connected to the soft starter (input terminals L1, L2, L3) in positive
phase sequence and Pr 5D Phase Sequence must be set to Positive only.
CAUTION
78
Electrical
Keypad
Quick Start
Installation
and
Commissioning
Status
N
E
F1
KA1
DI1 +24
V
C
SH
C
SL
C
SR
KA2
KA1
KA2
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Operation Programming Diagnostics
DI2
+24V
DI3
+24V
E
DI4 +24V
KA1
KA1
Zero speed detect
6
Zero speed sensor
7
A
Off (Ready)
B
Start
C
Run
Application
Technical
Maintenance Options
Examples
Data
A2
KA2
D
Stop
E
Zero speed
DI1, +24V
Start
DI2, +24V
Stop
DI3, +24V
Reset
Digistart IS User Guide
Issue: 4
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