Medium Voltage Contactor Dropout Time
Medium Voltage Contactor Dropout Time
(OP)
Medium voltage (4.16 kV system) vacuum contactor dropout time is important for fuse-contactor coordination. Some vendors have values between 15-25 ms, and others, several cycles, which I have been more used to seeing in the past. Compare that to a 3 or 5 cycle vacuum breaker, and 15-25 ms is extremely fast. Doe anyone have some insights on this?





RE: Medium Voltage Contactor Dropout Time
A 1-cycle contactor opening time is typically what I've seen and used for approximation. This is the amount it takes the contactor to open its contacts, not the for current to go to zero. Also, a contactor is not going to be interrupting fault current - at worst it must handle motor locked rotor or inrush current. Medium-voltage contactors may have delayed opening to allow the fuse time to clear faults.
RE: Medium Voltage Contactor Dropout Time
http://download.schneider-electric.com/files?p_Fil...
RE: Medium Voltage Contactor Dropout Time
RE: Medium Voltage Contactor Dropout Time
While the contactor drop out time is important, so is the overload setting, which depends on motor full load amperes. You can select a fuse that works well with the contactor, but crosses up with the overload. Many of these fuses do not like to trip on overload (low level) currents, and will fail catastrophically. All three items must be considered, so as DPC suggests, contacting the contactor manufacturer would be a good place to nail down one of the variables. Motor HP will determine the overload setting, and then you must "simply" select a fuse that fits between the two.
Dave
RE: Medium Voltage Contactor Dropout Time
RE: Medium Voltage Contactor Dropout Time
RE: Medium Voltage Contactor Dropout Time
Most contactors use a DC holding coil so it will take a little time before they begin to open after the power is removed. The dc current in the coil typically has to decay by passing through a freewheeling diode.
RE: Medium Voltage Contactor Dropout Time
RE: Medium Voltage Contactor Dropout Time
RE: Medium Voltage Contactor Dropout Time
RE: Medium Voltage Contactor Dropout Time
RE: Medium Voltage Contactor Dropout Time