
281
Issue C
5
%
Germany (0 91 87) 10-0 - USA (847) 827 - 7600 - UK (01296) 420336 - www.etacbe.com
Selection of the device
The contacts of type 2-7000 will open when energized so that the
lowest possible motor current (e.g. the running current of the motor
unloaded) must not be less than the current rating of the motor start
switch to ensure that the switch will reconnect the auxiliary phase after
completion of the starting process.
The current rating will determine both the switching characteristics and
ratings of the contacts.
At the same time the highest possible motor current (short-circuit
current at overvoltage) must not exceed 6 times the motor start switch
current rating. Normally the A-P-S current rating should be approx.
1/5 of the running current of the motor (see the examples below).
Either wiring a or wiring b should be chosen, giving due consideration
to these two extreme conditions.
Wiring information
Wiring with motor start switch (A-P-S)
Example for wiring a“:
Current of the motor unloaded
(current rating of the motor)
I
o
= 2.6 A = I
min
I
N
= 3.0 A)
Short-circuit current of the main phase
of main and auxiliary phase I
k Ha + Hi
= 12 A = I
max
I
k Ha
= 7 A
Formula for the motor start switch:
Current rating = 1/5 I
max
= 1/5 12 = 2.4 A
i.e. a motor start switch current rating of 2.5 A (e.g. 2-7000-P10-KF-2.5 A)
should be selected.
With wiring a“ the overall current of the motor flows through the
bimetal heater (terminal 1). The max. possible current of 12 A is lower
than 6 x 2.5 = 15 A, the highest admissible load for the motor start
switch. Furthermore the lowest possible motor current (2.6 A) is higher
than the motor start switch current rating, ensuring that the auxiliary
phase will remain disconnected even when the motor is unloaded.
Example for wiring b“:
Current of the motor unloaded:I
o
= 1.5 A = I
min
Other motor data as indicated in example a“.
As in this case the motor start switch current rating must be selected
according to the lower minimum current value, only the short-circuit
current of the main phase (7 A) may flow through the bimetal heater
(terminal 1) in order to prevent overloading.
Current rating = 1/5 I
k Ha
= 1/5 7 = 1.4 A.
i.e. a motor start switch current rating of 1.5 A (e.g. 2-7000-P10-KF-1.5 A)
should be selected.
The motor start switch rated at 1.5 A must be connected according to
wiring b“. In this case the max. possible load is 7 A, i.e. it is lower than
6 x 1.5 A = 9 A.
The current of the motor unloaded (1.5 A) equals the motor start switch
current rating - the auxiliary phase will again remain disconnected.
Wiring with E-T-A Circuit Breaker:
This
configuration
recommended where the
function of the device or
equipment is supervised and
resetting should only be made
manually (e.g. circular saws).
Operation of the motor start
switch is otherwise the same.
is
Once the motor has stopped, if
an attempt is made to start it
again before the motor start
switch has reset, a stall condition
will result causing the motor
protection control to disconnect
the supply. The motor start
switch contacts will reset, and
the motor may be re-started
once the motor start switch has
closed again automatically.
Wiring with Motor Protection Control (M-R):
2. Wiring b“:
This special connection is
suitable for motors with relatively
high short circuit currents:
Mains input:
Main phase:
Auxiliary phase: terminal 3
terminal 2
terminal 1
In this case it is only the main
phase current that determines
the switching time of the motor
start switch.
1. Wiring a“:
For this standard connection
please observe the following:
Mains input:
Main phase:
Auxiliary phase: terminal 3
terminal 1
terminal 2
The overall starting current of
the motor determines the
switching time of the motor start
switch and must not exceed its
max. current capacity.
Motor Start Switches
A-P-S
3
1
2
Hi
1
Ha
M
A-P-S
3
1
2
Hi
1
Ha
M
A-P-S
3
1
2
Hi
1
Ha
M
M-R
P
2
A-P-S
3
1
2
Hi
1
Ha
M
2
1
E-T-A