8I20 7
OPERATION
MOTOR CONNECTIONS
The U/V/W motor connections are the direct PWM outputs of the 8I20s bridge.
Larger motors may have enough winding to frame capacitance to generate considerable
ground noise. This noise source can be reduced by:
1. Make sure that the motor frame ground signal is returned to the frame ground on the
8I20 card.
2. Use a ferrite bead as a common mode choke around all phase wires, that is the U/V/W
motor wires pass through a single bead. Do not route the frame ground wire through the
bead. A suggested ferrite bead is: Laird-Signal Integrity Products 28B1122-100.
ENABLE INPUT
The 8I20 has a isolated 4-24V enable input. This input must be driven to enable
motor drive. If enable input is not driven, the 8I20 will go into a fault state, and turn off
motor PWM.
FAULT OUTPUT
The fault output is an isolated transistor (OPTO coupler) output. The fault output is
off in non-masked fault conditions and on in normal operation. The fault output can supply
a maximum of 5 mA of output current and will switch voltages up to 24 VDC. Normally the
fault outputs of all 8I20s would be wired in series.
FAULT CONDITIONS
The 8I20 monitors many parameters and reports fault conditions in the FAULT
register. When a non-masked fault occurs, the 8I20 turns off motor drive and the current
control loop. The following is a list of the fault conditions:
NAME
BIT
FUNCTION
WATCHDOGFAULT
0
Communication timeout fault
NOENABLEFAULT
1
No external enable fault
OVERTEMPFAULT
2
8I20 PCB temperature > 85C
CURRENTFAULT
4
8I20 high side overcurrent Fault