U.S. patent application number 13/133767 was filed with the patent office on 2012-04-05 for electrical power tool for operating with alternating current.
This patent application is currently assigned to METABOWERKE GMBH. Invention is credited to Bernd Wiesner.
Application Number | 20120081044 13/133767 |
Document ID | / |
Family ID | 41348193 |
Filed Date | 2012-04-05 |
United States Patent
Application |
20120081044 |
Kind Code |
A2 |
Wiesner; Bernd |
April 5, 2012 |
Electrical Power Tool for Operating with Alternating Current
Abstract
The invention relates to an electrical power tool, particularly
an electric hand power tool, for operating with alternating
current, having an electric motor, and electronic control device,
and an electrical power switch for actuating the electric motor,
wherein the electronic control device comprises a bias voltage
output and a detection input, connected to each other by means of a
voltage divider comprising a summation point and to the side of the
power switch facing the electric motor, and the control device is
further designed such that the potential at the detection input is
monitored after actuating the power switch and used for checking
whether the power switch is conducting, and that it is actuated
again if the power switch was not conducting or returned to the
non-conducting state during the monitoring, and that said checking
and any renewed actuation of the power switch is repeated within a
half-wave of the alternating voltage.
Inventors: |
Wiesner; Bernd; (Owen,
DE) |
Assignee: |
METABOWERKE GMBH
METABO-ALLEE 1
NUERTINGEN
DE
72622
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20110241577 A1 |
October 6, 2011 |
|
|
Family ID: |
41348193 |
Appl. No.: |
13/133767 |
Filed: |
December 11, 2008 |
PCT Filed: |
December 11, 2008 |
PCT NO: |
PCT/EP2008/010516 |
371 Date: |
June 17, 2011 |
Current U.S.
Class: |
318/249 |
Current CPC
Class: |
H02P 25/14 20130101 |
Class at
Publication: |
318/249 |
International
Class: |
H02P 25/14 20060101
H02P025/14 |
Claims
1. An electric power tool, in particular a handheld electric power
tool, for operating with alternating current, having an electric
motor, an electronic control device and an electric power switch
for actuating the electric motor, characterized in that the
electronic control device comprises a bias voltage output and a
detection input which are connected to one another and to that side
of the circuit breaker which faces the electric motor via a voltage
divider which has a summation point, and the control device is
further designed such that the potential across the detection input
after respective triggering of the power switch is monitored, and,
on the basis of this, a check is made as to whether the power
switch is on, and that it is triggered again if the power switch
was not on or had returned to the off state during monitoring, and
that this check and possibly renewed triggering of the power switch
is repeated with a half-wave of the AC voltage.
2. The electric power tool as claimed in claim 1, characterized in
that the power switch is a triac.
3. The electric power tool as claimed in claim 1, characterized in
that the electronic control device is designed such that the check
and possibly renewed triggering of the power switch are carried out
between 5 and at most 10 times, with a half-wave of the AC
voltage.
4. The electric power tool as claimed in claim 1, characterized in
that the electronic control device is designed such that the check
and possibly renewed triggering of the power switch is carried out
at most x times within a half-wave of the AC voltage, where
x=Thalf-wave/Ttriggering sequence.
5. The electric power tool as claimed in claim 1, characterized in
that the electronic control device is formed such that
post-triggering is performed immediately, as soon as the check of
the signal at the detection input has shown that the power switch
is off.
6. The electric power tool as claimed in claim 1, characterized in
that the electronic control device is designed such that the
triggering sequence lasts for 50-500 .mu.s.
7. The electric power tool as claimed in claim 1, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 5-40 .mu.s.
8. The electric power tool as claimed in claim 1, characterized in
that the electronic control device comprises a synchronization
input in order to detect the zero crossing of the respective
half-wave.
9. The electric power tool as claimed in claim 1, characterized in
that the bias voltage output is operated with a negative control
voltage during a positive half-wave, and with a comparatively
higher potential during a negative half-wave.
10. A method for operating an electric power tool as clamed in
claim 1 with alternating current, with an electric motor being
supplied with electrical energy by means of an electronic control
device by virtue of phase gating control using an electric power
switch, characterized in that monitoring is performed immediately
after initial triggering of the power switch by tapping off the
voltage at a summation point of a voltage divider and a check is
made as to whether the power switch is on, in that, after the
initial triggering, the power switch is triggered again if the
power switch was not on or had returned to the off state during
monitoring, and in that this check and possibly renewed triggering
of the power switch is repeated within a half-wave of the AC
voltage.
11. The electric power tool as claimed in claim 2, characterized in
that the electronic control device is designed such that the check
and possibly renewed triggering of the power switch are carried out
between five and at most ten times, with a half-wave of the AC
voltage.
12. The electric power tool as claimed in claim 2, characterized in
that the electronic control device is designed such that the check
and possibly renewed triggering of the power switch is carried out
at most x times within a half-wave of the AC voltage, where
x=Thalf-wave/Ttriggering sequence.
13. The electric power tool as claimed in claim 2, characterized in
that the electronic control device is formed such that
post-triggering is performed immediately, as soon as the check of
the signal at the detection input has shown that the power switch
is off.
14. The electric power tool as claimed in claim 3, characterized in
that the electronic control device is formed such that
post-triggering is performed immediately, as soon as the check of
the signal at the detection input has shown that the power switch
is off.
15. The electric power tool as claimed in claim 4, characterized in
that the electronic control device is formed such that
post-triggering is performed immediately, as soon as the check of
the signal at the detection input has shown that the power switch
is off.
16. The electric power tool as claimed in claim 2, characterized in
that the electronic control device is designed such that the
triggering sequence lasts for 50-500 .mu.s.
17. The electric power tool as claimed in claim 3, characterized in
that the electronic control device is designed such that the
triggering sequence lasts for 50-500 .mu.s.
18. The electric power tool as claimed in claim 4, characterized in
that the electronic control device is designed such that the
triggering sequence lasts for 50-500 .mu.s.
19. The electric power tool as claimed in claim 2, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 5-40 .mu.s.
20. The electric power tool as claimed in claim 3, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 5-40 .mu.s.
21. The electric power tool as claimed in claim 4, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 5-40 .mu.s.
22. The electric power tool as claimed in claim 1, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 200-300 .mu.s.
23. The electric power tool as claimed in claim 2, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 200-300 .mu.s.
24. The electric power tool as claimed in claim 3, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 200-300 .mu.s.
25. The electric power tool as claimed in claim 4, characterized in
that the electronic control device is designed such that the
triggering period of the power switch lasts for 200-300 .mu.s.
26. The electric power tool as claimed in claim 2, characterized in
that the electronic control device comprises a synchronization
input in order to detect the zero crossing of the respective
half-wave.
27. The electric power tool as claimed in claim 3, characterized in
that the electronic control device comprises a synchronization
input in order to detect the zero crossing of the respective
half-wave.
28. The electric power tool as claimed in claim 4, characterized in
that the electronic control device comprises a synchronization
input in order to detect the zero crossing of the respective
half-wave.
29. The electric power tool as claimed in claim 2, characterized in
that the bias voltage output is operated with a negative control
voltage during a positive half-wave, and with a comparatively
higher potential during a negative half-wave.
30. The electric power tool as claimed in claim 3, characterized in
that the bias voltage output is operated with a negative control
voltage during a positive half-wave, and with a comparatively
higher potential during a negative half-wave.
31. The electric power tool as claimed in claim 4, characterized in
that the bias voltage output is operated with a negative control
voltage during a positive half-wave, and with a comparatively
higher potential during a negative half-wave.
32. The electric power tool as claimed in claim 1, characterized in
that the bias voltage output is operated with a negative control
voltage of -5 volts during a positive half-wave, and with a
comparatively higher potential of zero volts during a negative
half-wave.
33. The electric power tool as claimed in claim 2, characterized in
that the bias voltage output is operated with a negative control
voltage of -5 volts during a positive half-wave, and with a
comparatively higher potential of zero volts during a negative
half-wave.
34. The electric power tool as claimed in claim 3, characterized in
that the bias voltage output is operated with a negative control
voltage of -5 volts during a positive half-wave, and with a
comparatively higher potential of zero volts during a negative
half-wave.
35. The electric power tool as claimed in claim 4, characterized in
that the bias voltage output is operated with a negative control
voltage of -5 volts during a positive half-wave, and with a
comparatively higher potential of zero volts during a negative
half-wave.
36. A method for operating an electric power tool as clamed in
claim 2 with alternating current, with an electric motor being
supplied with electrical energy by means of an electronic control
device by virtue of phase gating control using an electric power
switch, characterized in that monitoring is performed immediately
after initial triggering of the power switch by tapping off the
voltage at a summation point of a voltage divider and a check is
made as to whether the power switch is on, in that, after the
initial triggering, the power switch is triggered again if the
power switch was not on or had returned to the off state during
monitoring, and in that this check and possibly renewed triggering
of the power switch is repeated within a half-wave of the AC
voltage.
37. A method for operating an electric power tool as clamed in
claim 3 with alternating current, with an electric motor being
supplied with electrical energy by means of an electronic control
device by virtue of phase gating control using an electric power
switch, characterized in that monitoring is performed immediately
after initial triggering of the power switch by tapping off the
voltage at a summation point of a voltage divider and a check is
made as to whether the power switch is on, in that, after the
initial triggering, the power switch is triggered again if the
power switch was not on or had returned to the off state during
monitoring, and in that this check and possibly renewed triggering
of the power switch is repeated within a half-wave of the AC
voltage.
38. A method for operating an electric power tool as clamed in
claim 4 with alternating current, with an electric motor being
supplied with electrical energy by means of an electronic control
device by virtue of phase gating control using an electric power
switch, characterized in that monitoring is performed immediately
after initial triggering of the power switch by tapping off the
voltage at a summation point of a voltage divider and a check is
made as to whether the power switch is on, in that, after the
initial triggering, the power switch is triggered again if the
power switch was not on or had returned to the off state during
monitoring, and in that this check and possibly renewed triggering
of the power switch is repeated within a half-wave of the AC
voltage.
Description
FIELD OF THE INVENTION
[0001] The invention relates to an electric power tool, in
particular a handheld electric power tool, for operating with
alternating current, having an electric motor, an electronic
control device and an electric power switch for actuating the
electric motor.
BACKGROUND
[0002] Electric power tools of this kind are known. The electric
motor of electric power tools of this kind is typically supplied
with a generally single-phase AC mains voltage by phase gating
control. This is done in the manner of phase gating control by the
electric power switch being "triggered", that is to say switched to
the on state, by application of a control potential or control
current (triggering pulse) by the electronic control device, so
that a motor current can flow as a result of the voltage applied to
the electric motor. One problem which frequently arises is that of
so-called "faulty triggering", that is to say that the power switch
has not been switched to the on state or has returned to the off
state, for example because the triggering moment did not occur
after, but rather shortly before, a zero crossing of the motor
current, and therefore the power switch was deactivated, that is to
say switched to the off state, again by the following current zero
crossing.
[0003] In order to ensure reliable operation and rotation of the
electric motor, which is a universal motor in particular, it is
necessary to ensure that the power switch is duly switched to the
on state in accordance with prespecified powers as intended at the
correct time during a half-wave of the AC voltage, and also remains
in the on state.
[0004] To this end, it is feasible, for example, for triggering to
be monitored by measuring the voltage across the power switch. It
would also be feasible for the motor current to be measured;
however, a low-resistance measurement resistor which, for its part,
would in turn require an amplifier arrangement for the measurement
signal, would have to be used for this purpose. Both these measures
are complex and costly to implement in respect of hardware.
Outputting several triggering pulses one after the other at a
predefined time interval would result in the unnecessary
consumption of triggering current in the case in which the power
switch is duly in the on state. In addition, a power supply part
forming the several triggering pulses would have to be of
correspondingly complex design.
[0005] The present invention is based on the object of providing an
electric power tool of the type described in the introductory part
in which reliable actuation of the electric motor as intended and
as required is ensured in an economical manner.
[0006] According to the invention, this object is achieved by an
electric power tool of said type in that the electronic control
device comprises a bias voltage output and a detection input which
are connected to one another and to that side of the circuit
breaker which faces the electric motor via a voltage divider which
has a summation point, and the control device is further designed
such that the potential across the detection input after respective
triggering of the power switch is monitored, and, on the basis of
this, a check is made as to whether the power switch is on, and
that it is triggered again if the power switch was not on or had
returned to the off state during monitoring, and that this check
and possibly renewed triggering of the power switch is repeated
within a half-wave of the AC voltage.
[0007] Monitoring triggering of the power switch in this way using
a circuit arrangement having two resistors in conjunction with a
bias voltage output and a detection input of the electronic control
device, which typically comprises a microcontroller, is associated
with an extremely low level of possible costs of implementation in
respect of hardware. In addition, the requirements made of
programming of the electronic control device which is required for
this purpose are relatively low. All that is necessary following a
triggering pulse is that preferably continuous, that is to say not
only intermittent, monitoring of the potential across the detection
input of the control device be carried out. To this end, a signal
is available at the voltage divider and therefore at the detection
input immediately after triggering of the power switch, said
signal, in this way, allowing basically immediate assessment of the
state of the power switch (on or off).
[0008] Therefore, according to the invention, a check as to whether
the power switch has been triggered as intended and also
continuously remains in the on state is made by the control device
immediately after triggering of the power switch. If this is not
the case, this is detected by virtue of a change in signal at the
detection input of the control device and the further control
measures can be executed, specifically renewed triggering of the
power switch as required. The potential across the detection input
is again monitored immediately after this and a check is made as to
whether this further triggering of the power switch leads to
continuous "success" or whether the power switch returns to the off
state again, and therefore still further triggering is
initiated.
[0009] The power switch is advantageously a triac. The invention
can also be advantageously used in multi-phase systems.
[0010] The check and, if required, triggering of the power switch
are carried out at most ten times, in particular at most eight
times, in particular at most six times, and further particularly at
most five times, within a half-wave according to one embodiment of
the invention. It has proven advantageous for the number of checks
and, if required, triggering operations of the power switch to be
performed at most x times, where x=T.sub.half-wave/T.sub.triggering
sequence. In this case, T.sub.triggering sequence denotes the time
interval between two triggering operations which is predefined in
the control arrangement.
[0011] If it is established during the check that the power switch
is off, it may prove advantageous for post-triggering to be
performed immediately, that is to say as rapidly as possible, as
soon as the check of the signal at the detection input has shown
that the power switch is off. This may be the case, in particular,
when the power switch is initially triggered in the middle of a
half-wave.
[0012] However, it may also prove advantageous, in a development of
the invention, for the electronic control device to be designed
such that post-triggering takes place only after a predefined time
interval, so that the triggering sequence or T.sub.tiggering
sequence lasts for 5 to 500 .mu.s, in particular 100 to 500 .mu.s,
in particular 150 to 400 .mu.s and preferably 200 to 300 .mu.s.
This may be the case, in particular, when the power switch is
initially triggered at the beginning of a half-wave, for example
when the current zero crossing has not yet taken place (in this
case, immediate post-triggering would not lead to the desired
result since the following current zero crossing would re-open the
power switch).
[0013] The triggering period of the power switch lasts for
preferably 5 to 40 .mu.s, in particular 15 to 30 .mu.s.
[0014] The electronic control device advantageously comprises a
synchronization input in order to detect the zero crossing of the
respective half-wave. This is intended to prevent the power switch
from being triggered too early, that is to say, for example, during
a time interval when the actual motor current is "lagging", that is
to say is still ahead of the respective current zero crossing, on
account of inductive loads of the electric motor. In such a case,
the power switch could be switched to the on state by triggering,
but (as already mentioned above) it would immediately return to the
off state again at the subsequent zero crossing of the motor
current. Preferably exact triggering of the power switch in
relation to the half-wave of the relevant phase also proves
advantageous in order to actuate the electric motor as
required.
[0015] The electronic control device is further advantageously
designed such that the bias voltage output is operated with a
negative control voltage (low), in particular of -5 volts, during a
positive half-wave, and with a comparatively higher potential, in
particular zero volt, (high) during a negative half-wave.
[0016] The present invention also relates to a method for operating
an electric power tool having the features of claim 10.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Further features, details and advantages of the invention
can be found in the appended patent claims and in the illustration
in the drawing and the following description of a preferred
embodiment of the invention. In the drawing:
[0018] FIG. 1 shows a schematic illustration of power supply and
actuation in an electric power tool according to the invention;
[0019] FIG. 2 shows a flowchart for the actuation of the electric
power tool according to the invention; and
[0020] FIG. 3 shows an illustration of the current/voltage
parameters during operation of the electric power tool according to
the invention.
DETAILED DESCRIPTION OF THE INVENTION
[0021] FIG. 1 illustrates the supply of electrical power to an
electric motor 2 in an electric power tool according to the
invention. A phase L of an electrical AC mains voltage and the
neutral conductor N are illustrated. One electrical connection of a
winding of the electric motor 2 is connected to the phase L, and
the other is connected to the neutral conductor N with the
interposition of a power switch 4. An electronic control device
which is denoted overall by reference symbol 6 and has a
microcontroller 8 is also illustrated. The electronic control
device 6 or the microcontroller 8 is supplied with an operating
voltage of -5 V directly by the one phase L (operating voltage
input 10). A synchronization input 12 is also provided, and
therefore the electronic control device 6 can always be
synchronized with respect to a zero crossing of the voltage of the
relevant phase L, that is to say the time of control processes in
relation to the zero crossing of the voltage of the phase L of the
mains voltage can be temporally defined. The power switch 4, which
is preferably in the form of a triac, is actuated by means of a
control output 14 from the microcontroller 8 of the electronic
control device 6 by a control pulse (triggering pulse) being
applied to the power switch 4 in order to switch the power switch 4
to the on state, and therefore the present voltage of the phase L
is applied to the electric motor 2 and consequently a motor current
flows through the windings of the electric motor. The time of the
triggering pulse is selected by the electronic control device 6 to
be within a half-wave of the AC voltage, depending on the power
requirement. The shorter the time interval between the triggering
pulse and the preceding zero crossing of the AC mains voltage, the
greater the time integral with respect to electrical power which is
supplied to the electric motor 2. However, this is true only if the
power switch 4 continuously remains in the on state, that is to say
is closed, by virtue of the triggering pulse during the relevant
half-wave.
[0022] The control device 6 or the microcontroller 8 further
comprises a bias voltage output 16 and a detection input 18 which
are connected to one another and to a connection 28 of the electric
motor 2 via a summation point 20 of a voltage divider 26 which
comprises two resistors 22 and 24. Said connection is between the
electric motor 2 and the power switch 4, and therefore a potential
of the power switch 4 relative to the neutral conductor N can
ultimately be tapped off as a result. In this way, according to the
invention, a signal is applied to the detection input 18, it being
possible to monitor said signal following triggering of the power
switch 4 and it being possible for said signal to be used to check
the "switching state" of the power switch 4 by virtue of the
electronic control device 6.
[0023] If, immediately after a triggering pulse is emitted (via the
control output 14 from the electronic control device 6), it is
established by monitoring the potential across the detection input
that the power switch 4 is off or has returned to the off state, a
renewed triggering pulse is transmitted to the power switch 4 by
the electronic control device 6. This check and possible
re-triggering of the power switch 4 during a relevant half-wave of
the AC mains voltage can be carried out several times, specifically
in accordance with a first embodiment in such a way that
post-triggering is performed as rapidly as possible, that is to say
virtually immediately, if it is established that the power switch
is off, or in accordance with a second embodiment in such a way
that a triggering sequence of, in particular, 50 to 500 .mu.s is
realized in order to be able to use the available periods of the
respective half-wave in as optimum a manner as possible to supply
power to the electric motor 2. However, the supply can also
advantageously be restricted to a specific number of cycles.
[0024] FIGS. 2 and 3 show, using a flowchart and a voltage and
current profile, the operation of the electric power tool according
to the invention.
[0025] FIG. 3 shows, at the top, one oscillation period of a phase
of the AC mains voltage (denoted by mains sine wave). A triggering
pulse during the positive and subsequent negative half-wave of the
AC voltage of in each case I.sub.G, where I.sub.G is advantageously
between 1-50 mA, in particular approximately 25 mA, is illustrated
beneath said oscillation period with a corresponding orientation in
relation to the profile of the voltage of the phase. The bias
voltage which is applied to the voltage divider 26 via the bias
voltage output 16 of the control device 6 is illustrated beneath
said triggering pulse. Said bias voltage is, in the case
illustrated by way of example, -5 V (potential low) during the
positive half-wave of the AC mains voltage and 0 V (potential high)
during the subsequent negative half-wave of the AC mains voltage
(only by way of example).
[0026] The motor current flowing through a winding of the electric
motor 2 is illustrated in the row beneath the bias voltage. It can
be seen that, during the course of phase gating control, the motor
current flows only after the power switch 4 is triggered, that is
to say only when the power switch 4 is switched to the on state,
until the subsequent zero crossing of the AC mains voltage (or even
somewhat longer on account of inductive effects). The motor
voltage, that is to say the motor voltage which is dropped across
the two connections of the winding of the electric motor 2 in
question, is illustrated beneath the motor current. If the power
switch 4 is on and a motor current is flowing, the illustrated
motor voltage is dropped across the terminals of the electric motor
2.
[0027] In the same way, the voltage which is dropped across the
power switch 4 is illustrated beneath the motor voltage. Finally,
the voltage which is applied to the detection input via the
summation point 20 of the voltage divider 26 is illustrated in the
lowermost row of FIG. 3, said voltage being monitored for control
purposes and being used to check whether the power switch 4 is on.
In the event of successful triggering of the power switch during
the positive half-wave, a low potential (in particular
approximately -5 V) is applied to the detection input, specifically
until the next zero crossing of the AC mains voltage, but only if
the power switch remains in the on state until this time! During
the negative half-wave, the voltage across the detection input
continuously falls from high potential (in particular 0 V) to low
potential (-5 V), until the power switch is switched to the on
state as a result of a triggering pulse. The detection input then
jumps to high potential, it being possible for this, for its part,
to be evaluated by the control device 6 as a test parameter for
correct conduction of the power switch 4. Therefore, FIG. 3 shows
correct operation of the electric power tool, in the case of which
the power switch 4 is ideally closed, as intended, with each
triggering pulse, and therefore power is supplied to the electric
motor 2.
[0028] Operation of the electric power tool according to the
invention and the method according to the invention are also shown
with reference to the flowchart according to FIG. 2. The routine is
such that the electronic control device determines a triggering
time for the power switch 4 in accordance with the current power
requirement during a half-wave of the AC mains voltage in
accordance with programmed prespecifications. In order to correctly
position this specific time in relation to the half-wave in
question of the phase in question, the time of the zero crossing of
the AC mains voltage of this phase is monitored using the
synchronization input 12. As soon as the zero crossing is
established, a check is made as to whether the zero crossing is a
positive zero crossing or a negative zero crossing (a positive zero
crossing means the start of the positive half-wave). The flowchart
then continues with one or the other path. When there is a positive
zero crossing, that is to say at the start of the positive
half-wave, the right-hand path of the flowchart is applicable. The
potential "low", that is to say, for example, -5 V, is applied to
the bias voltage output. The triggering timer is started and, when
the triggering timer is run down (above triggering time) for the
first time during the half-wave in question in accordance with the
prespecification by the control device, a triggering pulse is
transmitted to the power switch 4 via the control output 14. The
potential across the summation point 20 is then monitored via the
detection input 18. If the potential produced is "low" and is
produced at the detection input 18 in this form, the power switch 4
is on, that is to say closed, and the mains voltage is applied to
the electric motor 2 in accordance with its profile.
[0029] If, however, the potential "low" is not produced at the
detection input 18, but rather the potential "high" is produced,
this is an indication that the power switch 4 has returned to the
off state. Immediate post-triggering and renewed monitoring and
evaluation of the potential across the detection input 18 then take
place. This is carried out cyclically, with the number of cycles
within one half-wave expediently being limited, reference being
made to this in the introductory part.
[0030] A corresponding profile for the negative half-wave can be
found in the path of the flowchart which is illustrated on the
left-hand side in FIG. 2.
[0031] During operation of the electric power tool according to the
invention or when executing the method according to the invention,
the electric motor can be actuated in an operationally reliable
manner with the least possible expenditure on hardware, with a
number of triggering pulses which is as low as possible being
required, and this being the case only when a preceding triggering
operation proves to be a faulty triggering operation or the power
switch returns to the off state for other reasons. Further
post-triggering is only performed after this, specifically
substantially immediately after a faulty switching state of the
power switch is established.
* * * * *