Mitsubishi Electric FR-A700 Series, Technical Manual

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532
SELECTION
z Inverter leakage currents
Leak current of an inverter without built-in EMC filter
(
) is 1mA.
Leak current of is as follow when turning
the EMC filter ON/OFF.
Input power conditions
(220V class: 220V/60Hz, 400V class: 440V/60Hz,
power supply unbalance within 3%)
(1) Calculation of the continuous leakage
current
The value of the leakage current depends on the
cable type, cable diameter, cable length from earth
leakage circuit breaker to inverter, cable length from
inverter to motor, and inverter output frequency. It is
roughly calculated from a value for the commercial
power supply (50Hz, 60Hz).
1) Leakage current from cables (Ig
1
, Ig
2
)
Measure the electrical path length from ground
fault interrupter to inverter input terminals and the
types and sizes of cables and calculate the
leakage current according to the information.
(Apply the value for the commercial power supply.
Harmonic components can be ignored.)
Measure the electrical path length from inverter
output terminals to the motor and the types and
sizes of cables, calculate the leakage current
according to this information and multiply the
calculated value several times in consideration of
the harmonic components. (about three times on
average, through it depends on the inverter output
frequency)
2) Leakage current from the motor (Igm)
Determine the capacities and the number of
motors, calculate the total leakage current using
the in-operation leakage current value in the
information and multiply the total value several
times in consideration of the harmonic
components.
(about three times on average, through it depends
on the inverter output frequency).
3) Leakage current of noise filter on inverter input
side (Ign)
When using the inverter-dedicated radio noise
filter (FR-BIF), add approximately 4mA (400V:
approx. 8mA) per filter.
* Leakage currents equivalent to one phase of three
phase three wires connection cable.
4) Leakage current in the inverter (Igi)
For the 200V class 1.5kW or more, all
capacities of 400V class, 200V class
2.2kW or more, and all capacities of 400V class,
the amount of the leakage currents changes by
the EMC filter ON
/
OFF connector.
(2) Selection of the rated sensitivity current
The rated sensitivity current, protective ground
resistance value, and continuous leakage current of
an electrical path are interrelated. From the
standpoint of protection from electric shock, the
relationship between the rated sensitivity current and
protective ground resistance value is important.
From the standpoint of unnecessary operation
prevention, the relationship between the rated
sensitivity current and leakage current cannot be
ignored.
1) Selection of the rated sensitivity current
Find the continuous leakage current using the
method described in paragraph (1) and use the
rated sensitivity current of more than 10 times
greater than the continuous leakage current,
considering a transient inrush current. Note that
when a breaker for harmonic and surge
suppression is used with the inverter circuit, the
harmonic components are cut. In this case, use
the value 10 times greater than the continuous
leakage current generated when a commercial
power supply is used.
2) Application to legally restricted areas
In some areas, the rated sensitivity current is
specified by the electrical facility standard,
occupational safety and health rules and indoor
wiring regulations. When installing the earth
leakage circuit breaker in such places, select the
rated sensitivity current in accordance with these
rules and regulations. If the rated sensitivity
current selected for a large continuous leakage
current cannot satisfy the rules and regulations,
take either of the following measures:
(a) When there are several loads, install an earth
leakage current breaker for each motor and
inverter.
(b) Reduce the length of the cable or increase the
distance from the ground.
3) Examination from the standpoint of electric shock
prevention.
Electric shock is divided into direct shock and
indirect shock. In Japan, protection is generally
provided against indirect electric shock. The
determination of the rated sensitivity current is
related to the contact voltage and the resistance
Voltage
(V)
EMC Filter
ON (mA) OFF (mA)
200 22 (1)
*
1
400 30 1
400 1 1
* For the 200V class 0.4K and 0.75K, the EMC filter is
always valid.
For the 200V class 0.75K and 1.5K, the EMC filter is
always valid.
The leakage current is 1mA.
E700 D700
A700 F700
Phase
grounding
Earthed
-neutral
system
A700
F700
(For the calculation of the continuous leakage
current, refer to the "Mitsubishi earth leakage
circuit breaker technical information".)
A700
F700