Connection And Installation - Mitsubishi Electric MDU-BN Instruction Manual

2.3 Connection and installation

● MDU Breaker cannot be used with the power side and load side reversed.
● Do not forcefully pull the connection cable between the MDU and MDU Breaker main unit (15 N or less). Doing so may loosen or disconnect
the cable.
● When installed to the MDU, if the MDU Breaker main unit cuts off a fault current and must be replaced with a new unit, also replace
the MDU. It cannot be reused.
● The connection cable between the MDU and MDU Breaker main unit forms a small-signal circuit. Install it at least 10 cm away from strong circuits.
Use with the area around the connector fixed in place, so that no external forces are applied to the connector connection area when opening/
closing the front door. When bending the cable, maintain a radius of at least 20 mm.
● The connector area used to connect to the MDU is insulated from the inside of the MDU Breaker main unit. The product will operate normally and
will not break even if the MDU Breaker main unit is powered with the connector area disconnected (open).
● If a MDU will be installed later, do so within 1.5 years from installing the MDU Breaker main unit.
● Do not insert and pull out cables from the connector area more than 20 times each on the MDU Breaker main unit and MDU.
● Pulling out the connection cable connector when MDU control power is applied may cause a MDU alarm or the like to be erroneously displayed.
If this happens, reset the alarm and clear the memory when pulling out the connector and starting use.
● Control power is required for the MDU. Apply the control power supply voltage shown on the MDU between the L1 and L2 terminals.
Measurement, display, electric energy pulse output, CC-Link communication, and MODBUS communication cannot be used without power.
Install a short-circuit protector (using a circuit breaker or fuse) to the control circuit.
● If using MDU Breaker with a single-phase two-wire circuit, connect it as shown in Figure 1. The left pole (1-phase) load side is a live part,
so be sure to insulate it.
Use the middle pole (2-phase) and the right pole (3-phase) current, and two voltage between the middle pole (2-phase) and the right pole (3-phase)
as measurement data.
Ignore the left pole (1-phase) current, as well as the voltage between the left pole (1-phase) and the middle pole (2-phase) and between the right
pole (3-phase) and the left pole (1-phase).
● If using MDU Breaker with a single-phase three-wire circuit, connect it as shown in Figure 2 below with the neutral line connected to the middle
pole (2-phase).
If the neutral line is connected to either the left pole (1-phase) or the right pole (3-phase), it will be impossible to measure with MDU.
A connecting wire of
5.5 mm or longer is
2
recommended on
the primary side.
Caution: Live part
Figure 1. Connection method in a single-phase
two-wire circuit
● Note that a three-pole MDU Breaker product cannot be used with a three-phase four-wire system.
The following table shows the items that can be measured when a three-pole product is used with a three-phase four-wire system.
Measurement item Status
○
Load current
○
Line voltage
×
○
Harmonic current
Electric power/
×
reactive power
Electric energy/
×
reactive energy
×
Power factor
●
MDU breaker can not be attached closely.
Secure a 30 mm wiring space on the right side of the circuit breaker and mount the main unit for wiring of the connection cable and installation of
the connector for the connection cable.
●
When installing the MDU in a box such as a switchboard or control panel, be careful of the ambient temperature.
Operating ambient temperature: Use within the range of -10 ° C to +40 ° C (however, the average value for 24 hours should not exceed +35 ° C).
If this condition is violated, it may lead to malfunction or loss of lifespan.
1 2 3
Line side
Load side
Load
×
Voltage phase, N phase
Between voltage phases,
Between voltage phase and N phase
×
Voltage phase, N phase
Caution
1
200 V
100 V 100 V
Figure 2. Connection method in a single-phase
three-wire circuit
Reason
No CT on N phase, so measurement not possible
No VT between N phases, so measurement not possible
No CT on N phase, so measurement not possible
No CT on N phase and no VT between N phases, so N phase not added
No CT on N phase and no VT between N phases, so N phase not added
No CT on N phase and no VT between N phases, so N phase not included
5
2 3
Line side
Load side