P O W E R A M P L I F I E R S
BRUSHLESS
MBA-6-60
Power Amplifiers
91
1. Select open-loop mode and switch
offset/test switch to "On"
2. Set current limit according to the
maximum motor current
3. Check power and connect it to the
amplifier
4. Connect HALL sensor inputs. LED
should be green. Turn motor shaft
manually one revolution. LED
should remain green. If not, change
60/120 degree phasing switch set-
ting (SW2)
5. Connect the three motor wires.
There are six ways to connect the
three wires to Motor-A, Motor-B,
and Motor-C pins. Try all six com-
binations and choose the best one.
If the motor runs more slowly in
one direction, or if you have to
move the shaft to start the motor,
the combination is incorrect
6. Adjust offset/test potentiometer for
zero speed, and then switch
offset/test switch to "Off"
7. Set mode suitable for your applica-
tion
Both peak and continuous current lim-
its are adjusted by Pot 2 at the same
time. The peak current limit is twice
the continuous limit and lasts for two
seconds. The potentiometer has 15
turns and is linear. Thus, to adjust the
current limit, turn the potentiometer
counterclockwise to zero, then turn
clockwise to the appropriate value. P1-
15 is the input to the internal current
amplifier stage. Because the output
current is proportional to P1-15, the
adjusted current limit can easily be
observed at this pin without connect-
ing the motor. The actual current can
be monitored at pin P1-8.
Setup
Current Limit Adjustment
Switch Functions
SWITCH
FUNCTION DESCRIPTION
SETTING
ON
OFF
1
Duty-cycle feedback
On
Off
2
120/60 degree commutation selection
120 degree
60 degree
3 This capacitor normally ensures "error-free" operation in
Shorts out the Off
velocity mode by reducing the error signal (output of
velocity/voltage loop
summing amplifier) to zero
integrator capacitor
4 Offset/test. Sensitivity of the "offset" pot. Used as an
Increase
Decrease
on-board reference signal in test mode.
Commutation Sequence
