12
Installation
On site fuse protection with current circuit-breaker
valid for motor version
without switch/with 3PTC
Depending on the process conditions and the intake pressure, the motor can be-
come overloaded, i.e. the power input can exceed I
N
. In cyclical operation, it is per-
missible for the current to temporarily exceed the rated current I
N
by 15%, provided
that the motor temperature is monitored by means of a thermistor.
Fuse protection with preset circuit-breaker in terminal box
valid for motor version
with switch/without 3PTC
Operating conditions that exceed the rated current I
N
for longer periods can trigger
the current circuit-breaker. In this case monitoring with a PTC temperature sensor
(3PTC) is not possible.
The Three Phase Cur-
rent Motor Circuit
Delta Connection
The three coils are connected in series with the connection point connected to the
mains. The voltage of each coil is the same as the mains voltage whereas the mains
current is the cube root of the coil current. Delta connections are denoted by the
symbol
∆
. The voltage between the mains supply lines is called mains voltage. The
mains current is the current which flows in the supply lines.
Fig. 7: Motor coil and connecting plate of Delta Connection
Star Connection
The ends of the three coils are connected at the star center. The terminal voltage is
the cube root of the coil voltage; the mains and the coil current are the same. Star
connections are denoted by the symbol
Y
. A star connection three phase motor for
400 V mains voltage has a coil voltage of 230 V.
Fig. 8: Motor coil and connecting plate of Star Connection
W2
U1
L1
V2
V1
W1
U2
L3
L2
W2
U2
V2
U1
V1
W1
L1
L2
L3
W2
U1
L1
V2
V1
W1
U2
L3
L2
W2
U2
V2
U1
V1
W1
L1
L2
L3
