Axis 670 Bedienerhandbuch PDF herunterladen (Seite 20)

After 2 additional seconds (3 seconds from tum-on), the second stage of U8 resets and the

following actions occur:

The error integrator is enabled via U15D.

The "position in" signal is enabled.

The scanner will begin to follow the input signal.

The "fault out" signal de-activates and the LED tums green.

3.13.2. Error Shutdown

There are several error states that the protection circuitiy is designed to detect and guard against.

They are:

Loss of position detector

signal:

If the cable is not plugged into the scanner or the servo, or if

there is a loss of position detector signal for any reason, the fault detector will see this. Va

and Vb have to be above a minimum voltage of 0.96 volts.

Position Signal. VP has exceeded +/- 10 volts: There are intemal mechanical stops within

the scanner that prevent it from spinning a fiill 360°., however during a fault state, the current

must be shut off before the rotor reaches these intemal stops. The electionics are set to sense

when the scanner has exceeded the maximum legal range, +/-20° mechanical. This is

accomplished by comparing the position signal (reduced by a factor of

two)

to the +VREF

and the -VREF levels. If Vpos exceeds either one, the fault detector will sense this over-

position and trip. Thus, the position output signal must be kept within +/-10 volts or the

servo will fault. On systems whose fieldsize has been set to +/-20° mech., the system may

trip whenever the edge of the field is approached (65535 and 0). Caution! Do not let the

system stay in this condition indefinitely. The scanner might be damaged.

Over-temperature: The coil temperature must be monitored at all times when the scanner is

being operated close to its performance limit. On the 670 board this is accomplished by the

"Coil Temperature Calculator" circuit. This circuit rectifies the current signal, then performs

an I^/R calculation to determine the power dissipated in the coil. Then, loiowing its thermal

time constant and thermal conductivity to the case, the temperature can be calculated. The

"90%

Max Power Warning" output signal on J4.6 will be activated when within 10% of

tripping the fault detector. The fault detector will trip and the "fault out" signal on J4.7 will

activate whenever the coil temperature reaches its maximum safe operating limit.

Loss of power: To ensure protection during "brown-outs", the servo will shut the system

down if the Input Power Voltages drop below a preset minimum. During system integration,

ensure that the power supplies and the power supply connections can meet the demands of

the scanner operated at the performance levels expected for the application. If not, the input

voltage will dip, and fault circuitry will activate. This can cause a fault "cycling" to occur.

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Axis 670 Bedienerhandbuch Seite 20