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Functional Description
7936 and 7937
fails. If the spindle speed does not measure 3000
rpm within approximately 13 seconds, the start
relay is turned off and spin up fails. Without a
successful spin up, no functional commands
(recalibrate, seek, etc.) can be executed.
5-121. BRAKE
VOLTAGE
SOURCE.
The
motor brake is an electromechanical device,
powered by 24 Vdc from transformer T1 and full-
wave rectifier CRI on PCA-A8.
The primary
windings of the transformer are connected to the
ac input via jumpers in the connector which con-
nects the motor leads to connector J I (" lIS Vac")
or J2 ("240 Vac") on PCA-A8. The windings are
connected in parallel for a 90-132 Vac input and
in series for a 180-264 Vac input.
The 24 Vdc
output from CR1 holds the brake off when the
drive LINE- switch is in the on position. When
power is turned off, the loss of DC voltage im-
mediately causes the brake to be applied.
5-122.
SPEED SENSOR
The speed sensor is a Hall-effect device mounted
adjacent to the spindle drive pulley. A magnet,
embedded in the pulley, triggers the sensor once
per revolution of the pulley. The sensor output,
labeled Speed Sense
(SPDSNS-L),
is connected to
the servo controller in servo PCA-AI.
5-123.
SERVO PCA-AI
The servo controller in servo PCA-A1 generates
Start Capacitor
(SCAP-L)
and monitors Speed
Sense
(SPDSNS-L)
during the drive spin up (start)
operation. This operation is discussed in the servo
system functional description.
5-124.
READ/WRITE PCA-A2
Signals
SPDSNS-L
and
SCAP-L
are routed
through read/write PCA-A2 and signal jumper
cable W7 to power distribution PCA-AS.
S-36
5-125.
POWER DISTRIBUTION PCA-A5
Power distribution PCA-AS receives Speed Sense
(SPDSNS-L)
from the speed sensor via Speed sen-
sor cable WS and routes the signal to servo con-
troller PCA-A1 via signal jumper cable W7 and
read/write PCA-A2. PCA-AS also supplies +SV to
the speed sensor via ca ble W S.
Signal Start Capacitor
(SCAP-L)
from servo
PCA-AI is routed through PCA-AS to the start
relay in primary power PCA-A8 via power supply
cable W4. PCA-AS also supplies +SV to the relay
via cable W 4.
5-126.
POWER SUPPLY SYSTEM
The power supply system develops DC operating
voltages from the ac line voltage and distributes
these voltages throughout the drive. The output
voltages are ±4SV unregulated; and ± 12V, +SV, and
-S.2V regulated. The power supply system also in-
cludes fault circuitry which shuts down drive
operation for over voltage, over current, under
voltage, or power supply overheating. Control sig-
nals Power On Reset
(POR-L)
and Power Fail
(PF-L)
are also generated by the system.
In addition, the signals from controller PCA-A6
which control the operation of the front panel
LED display are routed through the power supply
system cabling to LED PCA-A 7.
The power supply system consists of cable as-
semblies,
mainframe
wlnng,
primary
power
PCA-A8, power supply PCA-A4, power distribu-
tion PCA-AS, and circuits in servo PCA-AI and
read/write PCA-A2. See figure
iii.
The following paragraphs provide a more detailed
description of the power supply circuitry. Refer
to table S-I for a description of the mnemonics
used in the text and the functional block diagram.
Refer also to table 12-2 for detailed voltage dis-
tribution information.
5-127.
AC INPUT CIRCUIT
The ac line voltage is connected to the input of
power supply PCA-A4 via the power cord, line
filter FLI, primary power cable WI, the LINE-
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