General Remarks - Watt Drive L2000 Series Manual

General remarks

When connecting cables, the following items must be observed:
- When changing the power supply of the motor between the inverter and commercial power
line, be sure to install mechanically interlocked switches (S1 and S2) as shown in the figure
below:
- Install an earth leakage breaker at the input of the inverter. Select an earth leakage breaker
which has a short term delay and a higher trigger current.
When the cable between the inverter and the motor is more than 10 meters long, the thermal
relay may malfunction due to high-frequency waves. To prevent this, install an AC reactor on
the output side of the inverter or use a current sensor rather than a thermal relay.
- In case a relay is connected to the digital output terminals 11 or 12 be sure to install a surge
absorbing diode in parallel to the relay. Otherwise the surge voltage created when the relay
goes on or off may damage the output circuit.
- Be sure that the specified grounding is carried out. Separate the inverter´s grounding pole from
those of other heavy electric machinery and avoid using common grounding poles when
multiple inverters are employed.
- Use a twisted and shielded wire when connecting signal lines to the control terminals and cut
the shielded covering as shown in the figure below. Make sure that the length of the signal line
is 20 m or less. If the line must be longer than 20 m then an appropriate signal amplifier should
be used.
- Use relays which are capable of reliably switching at a voltage of 24VDC and a current of 3mA.
- Install the mains circuit cables at a safe distance from the control circuit cables. If the mains
circuit cables and the control circuit cables have to cross each other, this should be done at an
angle of 90 degrees because interference can be minimized in this case.
Earth leakage
circuit breakers
Power
supply
Inverter
Inverter 1
Inverter 2
Inverter 3
WRONG
Grounding point
Isolate here
Frame ground
Page 24 / 52
S1
L1(L1) T1(U)
Motor
L2 T2(V)
S2
L3(N) T3(W)
Inverter 1
Inverter 2
Inverter 3
CORRECT
Grounding point
No grounding
necessary here
Wiring