Page 31
© copyright 1992, 1996 by Powertec Industrial
Motors
6.4 POWER OUTPUT SECTION
The output transistors are turned on and off (no more
than two on at the same time) to supply current to the
Brushless motor as determined by the speed and load
regulation circuitry on the Speed and Current Controller
boards. Control power for the output transistors comes
from the base driver board (see Figure 28). The output
transistors are protected by snubber elements to suppress
high spikes and transients caused by switching high volt-
ages on an inductive load at high frequencies (up to 1.8
Kilohertz). “Free wheeling diodes” built into the transistor
packages carry circulating currents which occur when the
transistors are off.
It is very important that the terminals T1, T2, and T3
be connected to T1, T2, and T3 respectively on the motor.
The other connections at the motor end will vary with the
speed, horsepower, and voltage of the motor.
The Base Driver Board (part # 4001-144002-XXX)
is switched on and off by the Current Controller Board
through the P2 cable. The board serves the all six transis-
tors. An LED indicates that an output transistor is turned
on. These lights may be difficult to see when the motor is
lightly loaded due to the Pulse Width Modulation. The
length of time that the transistors are on is proportional to
load on the motor.
The Base Driver Board is supplied by four windings
on the transformer, one winding for each of the top transis-
tors, and one winding for all three of the bottom ones. The
Base Driver Board supplies raw power supplies (+24VDC
and -24VDC to common) to the other PC boards, so it gets
an extra winding connection (the green-green/yellow-green
winding) on its P1 connector.
The base and emitter wires going from the Base
Driver board are color coded to prevent mix-ups (Figure
30). IT IS VITALLY IMPORTANT THAT THESE
WIRES NOT GET MIXED UP. Connecting the wrong
wires to the wrong transistors on the output WILL DAM-
AGE THE CONTROL!
POSSIBLE PROBLEM:
MOTOR DOES NOT TURN.
1. Make sure T1, T2 and T3 are connected properly.
2. Make sure motor cable is properly connected.
3. Check for ENABLE on Current Controller Board.
4. Check to see if any Base Driver Board LED’s are lit.
5. Check for trip on Current Controller Board.
POSSIBLE PROBLEM:
INPUT FUSES BLOW WHEN THE RUN OR JOG
CIRCUIT IS ACTIVATED.
1. With power off (wait for the capacitors to discharge),
disconnect motor leads at T1, T2, and T3.
2. With an ohmmeter (preferably with a diode scale) check for
a shorted transistor in the output bridge.
3. If no shorted transistor is found, power up with the motor
leads T1, T2, and T3 disconnected. Turn speed pot to about
10%. If the fuses do not blow when run is commanded, check
the wiring to the motor for grounds or shorts..
POSSIBLE PROBLEM:
CURRENT LIMIT OR TRIP ON START OR JOG.
1. Make sure the shaft of the motor is free to turn.
2. Uncouple motor from load, and try to operate the motor.
3. Check motor connections, both power and cable.
4. Make sure that the HORSEPOWER CALIBRA-
TION resistor is installed on Capacitor Board.
CABLE TO P2
CURRENT CONTROLLER
P2P1
P11
P12
P13
P14
RED
YELLOW
RED
ORANGE
RED
BROWN
BROWN
BLACK
ORANGE
BLACK
YELLOW
BLACK
B1 E1 B4 E4 B2 E2 E5 B5 B6 E6 B3 E3
R R/W R
FROM XFMR
O O/W O
FROM XFMR
B B/W B
FROM XFMR
G G/W G
FROM XFMR
Y Y/W Y
FROM XFMR
Figure 30: Layout and connections of the base driver board 144-2.3.
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