SM-6495 - Ansaldo STS

General Maintenance and Troubleshooting2.7.1. Gate Arm Ascent and Descent Time Test (24-Volt Systems)This unit is equipped with a Power Down Relay. The Power Down Relay is used in the power downportion of operation (90° - 45°).1. Apply 24 VDC to the control line of the gate mechanism. This will raise the arm automatically tothe clear position.2. Measure the ascent time required to raise the arm from 0 to 90 degrees (horizontal to verticalposition). The ascent time is normally between 8 to 12 seconds.3. With the arm in the vertical position, check that the gap between the buffer and segment gear isabout 1/8”.4. Verify that the brake holds the arm in the up position.5. Remove the control voltage (set 0 VDC). Removing the voltage will force the brake to disengageand allow the arm to descend.6. Measure the descent-time. The descent time should be adjusted to railroad specification, (generally9 to 20 seconds). If necessary, adjust the snub resistor slide (refer to Figure 5-12 and Figure 5-13,Item 40) and retest the descent time. The fixed limit resistor (refer to Figure 5-12 and Figure 5-13,Item 42) on the right side of electrical assembly limits the current to the motor during the first 45°of the power down cycle.2.7.2. Circuit BreakerThe Model 95 is equipped with a self-restoring circuit breaker for the protection of the mechanism,batteries, etc., in the case of excessive current draw during ascent of the gate arm due to an obstruction.The circuit breaker is mounted on the electrical assembly, Figure 5-10, Item 35.The circuit breaker is rated at 20 amps on a 12VDC system and 10 amps on a 24VDC system. Thecircuit breaker is designed to carry 100% of the rating for approximately one-hour. At 125% of ratedcurrent, the unit opens within an hour, and at 200% of rated current, the unit opens within a minute.The circuit breaker on the pedestrian gate mechanisms is rated at 10 amps on a 12-volt system (seeFigure 5-14).The unit normally resets itself within a minute, and in most field applications, the unit opens within afew minutes.SM 6495, Rev. 7, December 2008 2-19