Current and Voltage Controls
1-Phase AC/DC Voltage - AC Current Control
Types SM 115, SM 125
• AC/DC voltage/current control relay
• Current measuring range: 0.5 - 500 AAC
through current metering transformer
• Voltage measuring range: 0.4 - 500 VAC/DC, divided
into 5 ranges
• Knob-adjustable set point
• Latching at set level possible
• Output: 10 A SPDT relay
• Plug-in type module
• S-housing
• LED-indication for power supply and output ON
• AC or DC power supply
Product Description
An AC/DC voltage and cur-
rent metering plug-in relay.
Often used where heating
elements are wanted to be
controlled for break or short-
circuit to avoid damage to the
equipment.
Ordering Key
Housing
Function
Output
Type
Power supply
Measuring range
SM 125 024 200
Type Selection
Plug
Output
Measuring ranges Supply: 24 VAC
SM 115 024
Supply: 115 VAC
SM 115 115
Supply: 230 VAC
SM 115 230
Supply: 24 VDC
SM 115 724
Current measuring
Circ. SPDT
0.5 - 500 AAC
Voltage measuring
Circ. SPDT
0.4 - 4 VAC/DC
2 - 20 VAC/DC
5 - 50 VAC/DC
20 - 200 VAC/DC
50 - 500 VAC/DC
SM 125 024 4
SM 125 024 20
SM 125 024 50
SM 125 024 200
SM 125 024 500
SM 125 115 4
SM 125 115 20
SM 125 115 50
SM 125 115 200
SM 125 115 500
SM 125 230 4
SM 125 230 20
SM 125 230 50
SM 125 230 200
SM 125 230 500
SM 125 724 4
SM 125 724 20
SM 125 724 50
SM 125 724 200
SM 125 724 500
Input Specifications
Input
Pins 5 & 7
Measuring ranges
Types
MI 5
MI 20
MI 100
MI 500
Types
voltage or current through
current transformer
Ranges
AAC RMS
0.5 - 5
2 - 20
10 - 100
50 - 500
Max. current
rms
20 AAC
50 AAC
250 AAC
700 AAC
SM 115 ...
SM 125 ... 4
SM 125 ... 20
SM 125 ... 50
SM 125 ... 200
SM 125 ... 500
Ranges Internal Max. volt.
VAC/DC resist. VAC/DC
0.4- 4*
8 kΩ
20
0.4- 4
8 kΩ
50
2 - 20 50 kΩ
100
5 - 50 100 kΩ
200
20 -200 450 kΩ
350
50 -500 1 MΩ
500
SM 125:
at AC voltages
peak value is measured
* only VAC
Latching
Interconnect pins 8 & 9
latching at set level
Specifications are subject to change without notice (27.10.99)
1
SM 115, SM 125
Output Specifications
Output
Rated insulation voltage
Contact ratings
(AgCdO)
Resistive loads
AC 1
DC 1
or
Small inductive loads AC 15
DC 13
Mechanical life
Electrical life
AC 1
SPDT relay
250 VAC (rms)
(cont./elect.)
µ (micro gap)
10 A/250 VAC (2500 VA)
1 A/250 VDC (250 W)
10 A/25 VDC (250 W)
2.5 A/230 VAC
5 A/24 VDC
≥
30 x 10
6
operations
≥
2.5 x 10
5
operations
(at max. load)
≤
7200 operations/h
Supply Specifications
Power supply AC types
Rated operational voltage
Through pins 2 & 10
024
115
230
Voltage interruption
Dielectric voltage
Rated impulse withstand volt.
Overvoltage cat. III (IEC 60664)
(IEC 60038)
24 VAC ± 15%, 45 to 65 Hz
115 VAC ± 15%, 45 to 65 Hz
230 VAC ± 15%, 45 to 65 Hz
≤
40 ms
2 kVAC (rms) (supply/elect.)
4 kV (1.2/50 µs) (line/neutral,
line/line), no direct connec-
tion to electronics
Overvoltage cat. III (IEC 60664)
(IEC 60038)
24 VDC ± 15%
None (supply/elect.)
800 V (1.2/50 µs)
2.5 VA
1.5 W
Operating frequency
Dielectric strength
Dielectric voltage
≥
2 kVAC (rms) (cont./elect.)
Rated impulse withstand volt. 4 kV (1.2/50 µs) (cont./elect.)
(IEC 60664)
Power supply DC types
Rated operational voltage
Through pins 2 & 10
724
Dielectric voltage
Rated impulse withstand volt.
Rated operational power
AC supply
DC supply
General Specifications
Hysteresis
Reaction time
10% ± 6%
Relay operates:
τ
= typ. 20 ms
Relay releases:
τ
= typ. 300 ms,
worst case reaction time may
be up to 5 x
τ
+ 5 to 15% on max.
(AC @50HZ)
≤
0.2%/ºC (≤ 0.11%/ºF)
LED, green (SM 115 only)
LED, red
(IEC 60947-1)
IP 20 B (IEC 60529)
2 (IEC 60664)
-20° to +50°C (-4° to +122°F)
-50° to +85°C (-58° to +185°F)
200 g
125 g
UL, CSA
Mode of Operation
SM 115
Example 1
AC current metering
The relay operates when the
current through the current
transformer reaches set point.
The relay releases when the
voltage drops below set point
(see hysteresis) or by inter-
rupting power supply.
Example 2
AC current metering
- latching
The relay operates when the
current through the current
transformer reaches set point
and latches in operating po-
sition. The relay releases by
removing the latch i.e. by
opening the contact between
pins 8 and 9, provided that
the current has dropped be-
low set point (see hysteresis),
or by interrupting power sup-
ply.
SM 125
Example 3
AC/DC voltage metering
The relay operates when the
voltage (peak voltage at AC)
reaches set point. The relay
releases when the voltage
drops below set point (see
hysteresis), or by interrupting
power supply.
Example 4
AC/DC voltage metering
- latching
The relay operates when the
voltage (peak voltage at AC)
reaches set point and latches
in operating position. The re-
lay releases by removing the
latch i.e. by opening the con-
tact between pins 8 and 9,
provided that the voltage in
all 3 phases has dropped be-
low set point (see hysteresis),
or by interrupting power sup-
ply.
Note:
At DC supply, do not connect
pins 7 and 10 as these pins
are internally connected via a
resistor of 3.9 kΩ. No current
must pass through this inter-
nal connection.
Accuracy
Input
Temperaturedrift
Indication for
Power supply ON
Output ON
Environment
Degree of protection
Pollution degree
Operating temperature
Storage temperature
Weight
AC supply
DC supply
Approvals
2
Specifications are subject to change without notice (27.10.99)
SM 115, SM 125
Wiring Diagrams
Example 1
Example 2
Example 3
Example 4
Black
Black
Latch
Latch
Power suppy
SM 115
Power supply
SM 115
Power supply
SM 125
Power supply
SM 125
PE = Pin 7
Range Setting
Range setting
Adjustment of set point on
relative scale.
Hysteresis
10% ± 6%.
The hysteresis may be exten-
ded to 75% by connecting a
resistor between pins 8 and 9.
Resistor limits are 1 MΩ and
15 kΩ. The hysteresis is increa-
sed by decreasing resistance.
Accessories
Sockets◊
Hold down spring◊
Mounting rack
Socket covers
Front mounting bezel
Current metering transformers
Potentiometer lock
S 411
HF
SM 13
BB 4
FRS 2
MI 5, MI 20, MI 100, MI 500
PL 1
For further information refer to "Accessories".
Operation Diagrams
Example 1 and 3
Power supply
Example 2 and 4
Power supply
Latching
Set value
Input voltage
pins 5 & 7
Relay ON
Hyste-
resis
Set value
Input voltage
pins 5 & 7
Relay ON
Hyste-
resis
Specifications are subject to change without notice (27.10.99)
3
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