Instruction manual

CHAPTER 6: SETPOINTS CONFIGURATION SETPOINTS
MM300 MOTOR MANAGEMENT SYSTEM – INSTRUCTION MANUAL 6–11
Ramp Down Time
Range: 0 to 125 seconds in steps of 1
Default: 1second
This setpoint specifies the time after signalling the inverter starter to ramp down before
the main contactor is opened, cutting power to the starter. If speed feed back is still on
when this time expires, a Drive Stop Fail alarm is issued.
6.2.1.7 Soft starter
The “Soft Starter” type is used with an external soft starter that ramps the motor speed up
on start and down on stop. Once the motor is ramped up, the soft starter can be bypassed.
When a start A control is received, the contactor A relay picks up and seals-in. This
provides power for the soft starter to start up and to drive the motor. The pre-contactor
relay (if any) is also picked up for the set
Pre-Contactor Time. When the pre-contactor timer
times out, the contactor B relay is picked up signalling the soft starter to ramp the motor
up. When a stop control is received, the contactors A and B relays drop out, signalling the
soft starter to ramp down.
Forced starts (for example, external start) operate in the same fashion as other starts, with
the B contactor not calling for the soft starter to ramp until the pre-contactor timer times
out.
If up to speed feedback is not received from the soft starter via the contactor B status
within the
Ramp Up Time setpoint during a start, a Drive Start Failed alarm is generated. If
soft starter speed feedback remains when the
Ramp Down Time expires during a stop, a
Drive Stop Fail alarm is generated. Neither results in a trip or a stop. The Drive Start Failed
alarm is latched until reset.
The B Open Contactor Control Circuit and B Welded Contactor alarms implemented in the
start/stop control element are defeated when the soft starter is selected.
If the soft starter does not provide an up to speed feedback signal, the contactor B relay
contact or an auxiliary contact of the B contactor should be connected to the up to speed
feedback contact input to suppress spurious Drive Failed To Start alarms.
The Undervoltage Autorestart feature is disabled for the Soft Starter.
The following figure illustrates typical starter timing beginning from the stopped state.
Figure 9: Typical starter timing for the soft starter
The following additional setpoints are available for the soft starter.
Start A Start B Start A Stop
Contactor B relay
Contactor A relay
Pre-contactor
Starting
Running
Motor current
Stopping
P
R
P = Pre-contactor time setting
R = Ramp Down time setting
853721A1.CDR