User's Manual

Turbo PMAC User Manual
Making your Application Safe 213
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t75.0Sumt
2
5.0
2
0
2
1SumSum ∆∆ +=−++=
Sum will increase at a rate of 0.75 per servo cycle. At the default servo cycle update rate of 2.25 kHz,
Sum will increase at a rate of 2250*0.75=1688 per second. If you want the motor to trip after 3 seconds
of this condition, you should set Ixx58 to 1688*3 = 5064.
When an integrated-current fault occurs on a motor, Turbo PMAC reacts just as for an amplifier fault
error. The offending motor is killed and possibly other motors as set by bits 21 and 22 of Ixx24. Turbo
PMAC sets the amplifier fault motor status bit. For an integrated-current fault, Turbo PMAC also sets a
separate integrated-current fault motor status bit. Both bits are cleared when the motor is re-enabled.
Note:
When Turbo PMAC is not commutating a motor with I
2
T protection, make sure
magnetization current parameter Ixx77 is still set to 0. In this setup, Ixx77 will not
affect operation, but it will affect integrated-current calculations.
Amplifier Enable and Fault Lines
The use of the amplifier-enable (AENAn) output and the amplifier-fault (FAULTn) input lines for each
motor are important for safe operation. Without the use of the enable line, disabling the amplifier relies
on precise zero offsets in Turbo PMAC’s analog output and the amplifier’s analog input.
Without the use of the fault line, Turbo PMAC may not know when an amplifier has shut down and may
not take appropriate action.
Note:
With the default sinking drivers for the amplifier enable signals, using the low-true
enable polarity (low voltage – conducting – is enable; high voltage – non-
conducting – is disabled) provides better failsafe protection against loss of power-
supply. If either the +5V supply for Turbo PMAC’s computational section, or the
+15V analog supply is lost, the amplifier will be disabled automatically, because
the output transistor will go into its non-conducting state. If you desire this failsafe
protection but cannot connect a signal of this polarity directly to the amplifier, you
must use intermediate circuitry to change the signal format. With the alternate
sourcing drivers, the high-true enable polarity provides better failsafe protection.
Encoder-Loss Detection
Most Turbo PMAC controllers have encoder-loss detection circuitry for each encoder input. Designed for
use with encoders with differential line-driver outputs, the circuitry monitors each input pair with an
exclusive-or (XOR) gate. If the encoder is working properly and connected to the Turbo PMAC, the two
inputs of the pair should be in opposite logical states – one high and one low – yielding a true output from
the XOR gate.
If the input circuits for the encoder have been configured so that both lines of the pair have pull-up
resistors (this is not the default – either an E-point jumper must be changed or a SIP resistor pack reversed
in its socket), then an encoder or cabling failure will cause both inputs into the same logical state, yielding
a false output from the XOR gate, and setting an error status bit. Note that in this setting, a single-ended
encoder cannot be used on the channel.