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Chapter 2 Installation and Wiring
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Safety categories defined by EN954-1 (JIS B 9705)
Category Safety requirement System behavior
Principle for achieving
safety
B
Components, safety-related parts of
control system, and protective equipment
must be designed, manufactured,
selected, assembled, and combined in
accordance with related standards to
ensure resistance to the anticipated
adverse effects of faults.
A defect (fault) may cause a loss of the
safety function.
1
The requirements of category B must be
applied.
Proven components and safety principles
must be applied.
A defect (fault) may cause a loss of the
safety function. However, the probability of
loss is less than that specified for category
B.
Characterized mainly by
the selection of
components
2
The requirements of category B and
proven safety principle specifications
must be applied. The safety function must
be checked by the machine control
system at appropriate intervals. The
requirements of category B and proven
safety principle specifications must be
applied. Safety-related parts must be
designed to meet the following
requirements:
- Any single defect (fault) in a part must
not cause any loss of the safety functions.
- If a single defect (fault) occurs, it must
always be detected when the safety
function can be reasonably implemented.
- A defect (fault) occurring during checking
may cause a loss of the safety function.
- A loss of the safety function is detected by
checking.
3
The requirements of category B and
proven safety principle specifications
must be applied. Safety-related parts
must be designed to meet the following
requirements:
- The safety function always operates
when a single defect (fault) occurs.
- Each single defect (fault) is eventually
detected to prevent the loss of the
safety function.
- The safety function always operates when
a single defect (fault) occurs.
- Almost all defects (faults) are detected.
- Accumulation of undetected defects
(faults) may cause a loss of the safety
function.
4
The requirements of category B and
proven safety principle specifications
must be applied. Safety-related parts
must be designed to meet the following
requirements:
- Any single defect (fault) in a part must
not cause any loss of the safety function.
- If a single defect (fault) occurs, it must
be detected when or before the next
operation request is made to the safety
function. If single defects (faults) cannot
be detected, the accumulation of
defects (faults) must not cause any loss
of the safety function.
- The safety function always operates when
a single defect (fault) occurs.
- Each single defect (fault) is eventually
detected to prevent the loss of the safety
function.
Characterized mainly by
the structure
Note: The system manufacturer is responsible for selecting the level of risk factors in accordance with EN954-1.
[Stop categories defined by EN60204-1]
The examples of wiring shown below are based on the three stop categories compliant with European Machinery
Directive EN60204-1.
- Category 0: (Uncontrolled) stopping by immediate removal of power to machine actuators
- Category 1: Stopping by removal of power after controlled stopping with power to machine actuators retained
- Category 2: Controlled stopping with power to machine actuators retained
Note: The Safe Stop function must be activated at least once a year for preventive maintenance purposes.
Note: Before preventive maintenance, the machine must be turned off. If the power supply to the motor is not turned
off during testing, the Safe Stop function will not operate. In such case, the inverter must be replaced.