AuCom CSX-007, Руководство по обслуживанию, Страница: 8 / 22

AVOIDING DAMAGE
710-02696-00C CSX Series Page 7
3.1 SCRs
SCR damage is generally caused by overcurrent, overvoltage or overtemperature. To prevent future damage, check
that the soft starter has been installed properly. Common causes of SCR problems include:
Overcurrent:
•
cable fault on soft starter output
•
motor fault
•
start current and/or start time exceeds the soft starter's rating
• starts per hour exceed the soft starter rating
Overvoltage:
•
power supply transient or surge
•
lightning strike (direct or indirect) on power supply
• motor fault
• loose connection in power circuit, before or after the starter
•
power factor correction connected to the output of the soft starter
•
over-corrected bulk power factor correction on a lightly loaded system causing severe ringing voltages
Overtemperature:
•
blocked heatsinks or restricted ventilation
•
inadequate ventilation
•
excessive ambient temperatures
• bypass relay fails to close during running
Protecting SCRs
Modern SCRs are generally rugged and reliable. However, the risk of SCR damage can be reduced by using
semiconductor fuses and/or a main contactor.
• Semiconductor Fuses
Semiconductor fuses reduce the potential for SCR damage caused by short circuits on the output of the starter.
Protection systems such as circuit breakers or HRC fuses do not operate quickly enough to protect SCRs from short
circuits.
• Main Contactors
SCRs are most vulnerable to overvoltage damage when voltage is applied to their input terminal while they are off. In
this condition the SCR is blocking the full line voltage. Using a main contactor to remove voltage from the SCR input
when the starter is off eliminates the risk of SCR damage due to overvoltage.
3.2 Output Relays
CSX Series soft starters have one fixed output relay (terminals 13, 14) and CSX i soft starters have one fixed and one
programmable output relay (terminals 13, 14 and 23, 24). These relays are often used to control the main contactor.
The electronic contactor coils used in many contactors have a high initial inrush current, which can damage the soft
starter's internal relays if the contactor coil is switched directly.
Using the Soft Starter to Switch a Contactor
Before using the soft starter's output relay to switch an electronic contactor coil, consult the contactor manufacturer.
Some contactor manufacturers (eg Klockner-Moeller) state that you cannot use PCB mount relays for direct switching
of their electronic contactor coils.
If this is the case, there are two solutions:
1. Use the soft starter's output relay to control a slave relay. This slave relay can then be used to directly switch the
electronic contactor coil circuit.
Section 3 Avoiding Damage