3 Phase 3 wire Three Phase Voltage Monitoring Relay under-voltage
protective device
In daily life, the loads we touch, such as electric lamps,
televisions, refrigerators, fans and other household appliances and
single-phase motors, are operated with two wires in the circuit,
which are all single-phase loads. In the three-phase four-wire
system, multiple single-phase loads should be connected as far as
possible to the three-phase circuits, rather than being
concentrated in one of the three circuits. If the impedance and the
nature of the load connected to each of the three-phase circuits
are the same, the loads in the three circuits are symmetric. Under
load symmetry, because the phases of the phase currents differ from
each other by 120°, the sum of the currents flowing through the
neutral line at each moment is zero, and the neutral line is
removed, and it is possible to supply power using a three-phase
three-wire system.
However, in reality, the three-phase load formed by a plurality of
single-phase loads connected to the three-phase circuit may not be
completely symmetrical. The midline is particularly important in
this case, not dispensable. The voltage across the load of each
phase of the neutral line is always equal to the phase voltage of
the power supply and will not change due to the asymmetry of the
load and the change of the load, just as each phase of the power
supply separately supplies the load of each phase separately. Can
work properly. If there is no neutral line under the condition of
asymmetric load, three-phase three-wire power supply with
asymmetrical load is formed. Due to the asymmetry of the load
impedance, the phase current is also asymmetric and the load phase
voltage is naturally not symmetrical. Some phase voltages may
exceed the rated voltage of the load, the load may be damaged (bulb
burned), some phase voltages may be low, and the load may not work
properly (bulbs dimmed). As in the figure, the load impedance of
each phase changes due to lighting, turning off the lamp, and other
factors. Both the phase current and the phase voltage change, the
light turns on and off, and other electrical appliances cannot work
properly or even become damaged.
Bad. It can be seen that in the three-phase four-wire power supply
line, the neutral line plays a role in ensuring that the load phase
voltage is symmetrical and unchanged. For an asymmetrical
three-phase load, the neutral line cannot be removed, fuses or
switches cannot be installed on the midline, and it is necessary to
use The steel wire with better mechanical strength serves as the
center line.
♦ Features
-- Compact modular size
-- Three-phase monitoring of phase sequence, phase loss, over- and
undervoltage and phase unbalance
-- Powered by the measuring circuit
-- 2 C/O contacts
-- 5 LEDs for status indication
♦ Protective Functions
-- Phase sequence
-- Phase loss
-- Overvoltage
-- Undervoltage
-- Phase unbalance
♦ Typical Applications
• Pumps • Fans
• Blowers • Motors
• Compressors
♦ Approvals
• CE • CCC
♦ Technical data
| Type | JVRD-380 |
| Measuring circuit | L1,L2,L3 |
| Rated voltage | 220VAC,380VAC,440VAC 460VAC,480VAC,50/60Hz |
| Monitoring functions | phase sequence,phase loss,overvoltage, undervoltage,phase unbalance |
| Voltage setting range | | Type suffix | Overvoltage | Undervoltage | | blank | +15% | -15% | | A | +10% | -10% | | B | +12.5% | -10% | | C | +15% | -12.5% | | T | Customized |
|
| Indicators | phase sequence,phase loss,overvoltage, undervoltage and normal |
| Output contacts | 2 C/O |
| Contact capacity | 6A,250VAC |
| Dimensions(H*W*D) | 79*23*79mm |
| Mounting | DIN Rail |
