TECO F33 Series, Instruction Manual, Page: 28 / 192

Control Connections 25
4.5.2 Types of control signals
Always make a distinction between the different types
of signals. Because the different types of signals can
adversely affect each other, use a separate cable for
each type. This is often more practical because, for
example, the cable from a pressure sensor may be con-
nected directly to the variable speed drive.
We can distinguish between the following types of con-
trol signals:
Analogue inputs
Voltage or current signals, (0-10 V, 0/4-20 mA) nor-
mally used as control signals for speed, torque and PID
feedback signals.
Analogue outputs
Voltage or current signals, (0-10 V, 0/4-20 mA) which
change slowly or only occasionally in value. In general,
these are control or measurement signals.
Digital
Voltage or current signals (0-10 V, 0-24 V, 0/4-20 mA)
which can have only two values (high or low) and only
occasionally change in value.
Data
Usually voltage signals (0-5 V, 0-10 V) which change
rapidly and at a high frequency, generally data signals
such as RS232, RS485, Profibus, etc.
Relay
Relay contacts (0-250 VAC) can switch highly inductive
loads (auxiliary relay, lamp, valve, brake, etc.).
Example:
The relay output from a variable speed drive which con-
trols an auxiliary relay can, at the moment of switching,
form a source of interference (emission) for a measure-
ment signal from, for example, a pressure sensor.
Therefore it is advised to separate wiring and screening
to reduce disturbances.
4.5.3 Screening
For all signal cables the best results are obtained if the
screening is connected to both ends: the VSD side and
the at the source (e.g. PLC, or computer). See Fig. 33.
It is strongly recommended that the signal cables be
allowed to cross mains and motor cables at a 90°
angle. Do not let the signal cable go in parallel with the
mains and motor cable.
4.5.4 Single-ended or double-ended
connection?
In principle, the same measures applied to motor
cables must be applied to all control signal cables, in
accordance with the EMC-Directives.
For all signal cables as mentioned in section 4.5.2 the
best results are obtained if the screening is connected
to both ends. See Fig. 33.
Fig. 33 Electro Magnetic (EM) screening of control signal
cables.
Signal
type
Maximum wire size
Tightening
torque
Cable type
Analogue Rigid cable:
0.14-2.5 mm
2
Flexible cable:
0.14-1.5 mm
2
Cable with ferrule:
0.25-1.5 mm
2
0.5 Nm
Screened
Digital Screened
Data Screened
Relay Not screened
NOTE: Each installation must be examined carefully
before applying the proper EMC measurements.
Control board
Pressure
sensor
(example)
External control
(e.g. in metal housing)
Control consol