Acs880+N5350 3-Wire Operating Mode Example; Manual Motor Disconnect Switch - ABB ACS880+N5350 User Manual

11.2 ACS880+N5350 3-Wire Operating Mode Example

The 3-Wire Operating Mode is provided for those customers that wish to control their cooling tower fan using what is
traditionally called "3-Wire Control". This method of control utilizes a momentary normally open "Start" pushbutton to
run the fan and a momentary normally closed "Stop" pushbutton to stop the fan. On power loss to the drive, the "start"
pushbutton will restart the drive when power is restored.

11.2.1 Manual Motor Disconnect Switch

This diagram depicts an example of using the CTD 3-Wire Operating Mode along with a manual disconnect switch between
the drive and the motor. The disconnect switch used in this diagram is a 3 position switch. The intent here is to provide one
position that is used when the fan is actually being run by the ACS880+N5350. There is a neutral position where the motor
leads are open circuit, and also a position which shorts the motor leads together. The position that shorts the leads together
is used to prohibit hazardous voltages from being present on the motor leads when it is disconnected from the drive should
the fan rotate. This could occur since the motor includes permanent magnets in its rotor thus giving it the characteristics
of being a generator when not connected to a drive. Another benefit of this position is that it will cause the motor to resist
windmilling. Note that it is required to provide an auxiliary contact on the disconnect switch that is open any time the motor
is not connected to the drive. This contact needs to be of the "Late Make / Early Break" style such that the contacts on the
auxiliary open before the power contacts open. Additionally, when the disconnect switch is closed, the power contacts of
the disconnect switch must close prior to the closure of the auxiliary contact.
Figure 11-2 ACS880+N5350 3-Wire Manual Motor Disconnect Switch
Input Disconnect
SW1
Fuses
Input
Power
Fan
Speed
Setting
Trickle Current
SW2 (Aux)
Late Make / Early Break
(closed when SW2 is in
the ACS880 position only)
3AXD50000011888
Line
Reactor
ACS880+N5350+P934
L1
L2
L3
XAI
1 +10V DC Analog Ref. Power
2 - VREF
3 Analog Common
4 AI1+ Speed Reference
5 AI1-
6 AI2+
7 AI2-
J1 AI1 Current/Voltage Jumper
J2 AI2 Current Voltage Jumper
XAO
AO1
1
AGND
2
AO2
3
AGND
4
De-Ice
XDIO
1 DIO1 Trickle Current Enable
2 DIO2 De-Ice Enable
Start
XDI
1 DI1 Start
2 DI2 Stop
Stop
3 DI3 ACC/DEC Time Set 1 (0) / Set 2 (1)
4 DI4 Constant Speed 2 (1 = On)
5 DI5 Fault Reset
Reset
6 DI6 Vibration Switch (External Trip)
T1/U
T2/V
T3/W
XD24
Motor Thermostat Input
DIIL 1
+24 VD 2
DICOM 3
+24 VD 4
DIOGND 5
Ground Select J6
XR01, XR02, XR03
RO 1 NC 1
COM 2
RO 1 NO 3
RO 2 NC 1
COM 2
RO 2 NO 3
RO 3 NC 1
COM 2
RO 3 NO 3
Output Disconnect
SW2
Cooling Tower Motor
M
Customer Supplied
Vibration Sensor
Input Power
Power Source
N.C. Dry
Contact Out
Customer Supplied
Vibration Switch
Note: Power wiring to be in separate conduits from signal
wiring such as thermostat and vibration switch.
Example Jumper Settings
J1
AI1 Voltage
J2
AI1 Current
Bus is terminated
J3
Bus not terminated
DICOM and DIOGND
connected (default)
J6
DICOM and DIOGND
separated
Example Connection Diagrams 11-3