MPM_DMS Accessories.D01 Page 1 of 4
DMS Accessories
50mV and 100mV Base-mounted DC Shunts
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Murata Power Solutions’ 50mV and 100mV base-mounted current shunts
are designed for measuring dc currents from 5A to 1200A. These preci-
sion shunts (+/–0.25% accuracy) connect directly to MPS’s DCA5-20PC
Series of dc ammeters. Installation is straightforward: simply connect the
load circuit to the shunt’s threaded studs and the shunt’s mV Kelvin-
outputs to the digital ammeter’s input terminals.
All models feature a rugged phenolic base that provides 750V isolation
to the shunt’s brass terminals, allowing for direct attachment to metal
surfaces. A highly stable (+/–15ppm/°C) manganin sensing-element
provides a wide –40 to +60°C operating temperature range. Please see
the DCA5-20PC data sheet for additional ammeter-related information
and detailed connection diagrams.
General Specifi cations (All Models)
Rated Accuracy ±0.25% max.
Sensing Element Manganin
Terminal Posts/Screws Brass
Tightening Torgue See Mechanical Dimensions
Current Rating See Selection Guide
Operating Temperature –40 to + 60°C (–40 to +137°F)
Technical Notes
IMPORTANT! To ensure safe and reliable operation, dc shunts and all
associated equipment must be installed and serviced by qualifi ed
technical personnel. Never make any connections to the shunt, the
load, or the ammeter with energized power sources. Contact Murata
Power Solutions if you have any questions regarding the installation
or operation of any of our instruments and accessories.
1. Base-Mounted Shunt Precautions: DC current shunts are low value
resistors that develop a mV output when current passes through their
highly-stable manganin resistive element. Under high current, contin-
uous use operation, dc shunts will dissipate considerable power and
may undergo a signifi cant temperature rise. For example, if allowed
to operate continuously at its full rated load, a 500A/50mV shunt
dissipates 25 Watts (500A x 0.050V = 25 Watts). Therefore, whenever
possible, be sure to specify 50mV shunts due to their inherently lower
power dissipation and voltage drop.
To ensure that the manganin sensing element does not exceed 125°C
under worst case operating conditions, please read and follow the guide-
lines in the mounting and derating sections of this data sheet. Tighten
all connections on the shunt per the torque specifi cations given in the
mechanical dimensions and selection guide on page 3. Please note, the
user is responsible for selecting the correct wire sizes (gauge) and wire
type for the given application.
2. Mounting Considerations: All shunts should be mounted with their resis-
tance blades in a vertical position to allow for natural convection cooling
(see Figure 1). Forced-air cooling must be provided when vertical mounting
is impractical, or in installations where the shunt is installed in a confi ned
location. The shunt’s manganin blades must never be allowed to exceed
+125°C; doing so will cause permanent damage to the shunt.
Shunts must be installed in a manner that protects them from damage due
to thermal expansion forces produced by high- or short-circuit currents. In
most cases, shunts are weaker than their external-circuit connections, so
provisions for additional wiring-fl exibility may be required in high current
and/or high-vibration applications.
Whenever practical, all shunts should be connected in the grounded side
(normally the ‘chassis’) of the dc supply. However, these shunts must be
connected in the grounded side of the circuit when the dc supply exceeds
750 volts (the rated limit for the shunt’s phenolic insulating base). When
more than one wire is to be connected to each end of a shunt, the wires
must be evenly distributed between both terminals (see Figure 1).
Figure 1. Typical installation
LOAD
CURRENT
50mV
OUTPUT
Mount shunt on a vertical surface
50mV50A
MPM_DMS Accessories.D01 Page 2 of 4
DMS Accessories
50mV and 100mV Base-mounted DC Shunts
www.murata-ps.com/support
–
–
–
+
+
+
LOAD
50mV SHUNT
DC SUPPLY
POWER
GROUND
(0Vdc)
LOAD CURRENT
0-50mV
OUTPUT
The following formulas can be used to calculate the maximum pulsed-
current (Ipuls) for a given shunt:
Where
Ipuls = Maximum pulsed current
Ppuls = Maximum pulsed power
Pa = 0.667 x shunt’s rated power at 25°C ambient
D = Ratio of ON TIME to ON TIME + OFF TIME
(period not to exceed 5 minutes)
K1 = Pulsed-operation rating factor (the square root of D)
R = Shunt’s resistance (see selection guide for values)
Example: An 800 Amp 50mV shunt will be operated for 15 seconds
each minute. What is the maximum current this shunt can carry
during the 15-second ON time?
D = 15/60 = 0.25 and = 0.5
Pa = 0.667 (800A x 0.050V) = 26.7 Watts
Ppuls = Pa/K1= 26.7W/0.5 = 53.4 Watts
3. Lead Extensions: The shunt’s Kelvin outputs (i.e., their 50mV or 100mV
output signal) should not exceed 24 inches in length (61cm), assuming
22AWG (0.5mm2) wire is used. If longer leads are necessary, the
additional voltage drops in the leads must be taken into consideration
as they will degrade accuracy and stability. However, MPS’s DCA5 series
dcammeters feature a calibration potentiometer that can be used to
compensate for some additional losses when long leads are employed;
contact MPS for calibration information.
4. Continuous-Operation Derating: If continuous operation is required,
a shunt must only be allowed to carry 2/3 of its maximum nameplate
amperage. The 2/3 derating factor provides an adequate safety margin
for convection cooled shunts operating in an ambient temperature of
+25°C. The following two sections contain additional derating that is
required when shunts will be exposed to higher operating temperatures
or pulsed (intermittent) currents.
5. Temperature Derating: If the shunt is to be operated at ambient
temperatures above +25°C, the maximum continuous current must
be further derated from the 2/3 value previously noted.
To fi nd the maximum permissible continuous current (Ie) at an elevated
temperature (Te), one must fi rst calculate the maximum allowable
power dissipation (Pe) at Te, using the following formulas:
Pe = Pa x [1-(Te-25°C)/100°C], and
Where
Ie = Maximum permissible continuous current at elevated
temperature
Te
Pe = Maximum power dissipation at the elevated temperature Te
R = Shunt’s resistance (see selection guide for values)
Pa = 0.667 x shunt’s rated power at 25°C ambient
Te = Elevated temperature
Example: How much current can a 150 Amp 50mV shunt safely carry
at an ambient temperature of +100°C?
Te = +100°C
Pa = 0.667(150A x 0.050V) = 5.0 Watts
Pe = 5.0W[1-(100-25)/100] = 5.0W x (1-0.75) = 1.25W
R = 0.00033 Ohms
Lastly, use the formula to fi nd the maximum derated
continuous-current at Te = +100°C:
6. Intermittent (Pulsed) Operation: Shunts that will not be exposed to
continuous operation at 2/3 rated current can be operated at levels
close to, oreven above, their nameplate ratings for portions of short
periods of times (5 minutes maximum) at 25°C ambient.
Ie = Pe
R
Ie = Pe
R
K1 = 0.25
Ie = 1.25W
0.00033Ω = 61.5A
K1 = D
Ipuls = Ppuls/R, and Ppuls = Pa/K1, and
Ipulsed = 53.4W
0.0000625Ω= 924A
–
+
–
–
+
+
LOAD
50mV SHUNT
DC SUPPLY
POWER
GROUND
(0Vdc)
LOAD CURRENT
0-50mV
OUTPUT
Figure 2. Typical Low-Side Shunt Connections
Figure 3. Typical High-Side Shunt Connections
MPM_DMS Accessories.D01 Page 3 of 4
DMS Accessories
50mV and 100mV Base-mounted DC Shunts
www.murata-ps.com/support
1.00
(25.4)
0.20 (5.08) Dia.
1/4 UNF Stud
1/4-28 UNF Hex Jam Nut
8-32 Screw
0.87
(22.0)
0.50
(12.7)
0.56
(14.2)
0.50
(12.7)
1.25
(31.7)
1.68
(42.7)
0.62
(15.7)
2.00
(50.8)
1.5
(38.1)
8-32 Screw
3/8-16 x 5/8
0.62
(15.7)
0.62
(15.7)
0.43 (10.9)
1.75
(44.4)
1.75
(44.4)
0.75 (19.0)
0.56
(14.2)
3.25
(82.5)
0.20 (5.08) Dia.
5 through 150 Amps
Part No.
Rated
Current/Output
Resistance
(Ωs at 25˚C) Torque Range
3020-01097-0 5A/50mV 0.01 36-40 in-lbs (4.1-4.5Nm)
3020-01107-0 10A/100mV 0.01 36-40 in-lbs (4.1-4.5Nm)
3020-01098-0 20A/50mV 0.0025 36-40 in-lbs (4.1-4.5Nm)
3020-01096-0 50A/50mV 0.001 36-40 in-lbs (4.1-4.5Nm)
3020-01099-0 100A/50mV 0.0005 36-40 in-lbs (4.1-4.5Nm)
3020-01108-0 100A/100mV 0.001 36-40 in-lbs (4.1-4.5Nm)
3020-01100-0 150A/50mV 0.00033 36-40 in-lbs (4.1-4.5Nm)
8-32 Kelvin output screws (all shunts): 14-15 in-lbs (1.58-1.69Nm)
200 through 500 Amps
Part No.
Rated
Current/Output
Resistance
(Ωs at 25˚C) Torque Range
3020-01101-0 200A/50mV 0.00025 14-15 ft-lbs (19.0-20.3Nm)
3020-01102-0 300A/50mV 0.000167 14-15 ft-lbs (19.0-20.3Nm)
3020-01103-0 500A/50mV 0.0001 14-15 ft-lbs (19.0-20.3Nm)
8-32 Kelvin output screws (all shunts): 14-15 in-lbs (1.58-1.69Nm)
MECHANICAL SPECIFICATIONS
MPM_DMS Accessories.D01 Page 4 of 4
DMS Accessories
50mV and 100mV Base-mounted DC Shunts
www.murata-ps.com/support
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifi cations are subject to change without
notice. © 2015 Murata Power Solutions, Inc.
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfi eld, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
This product is subject to the following operating requirements
and the Life and Safety Critical Application Sales Policy:
Refer to: http://www.murata-ps.com/requirements/
2.16
(54.9)
8-32 Screw
1/2-13 x 7/8
1.00
(25.4)
1.00
(25.4)
0.53 (13.5)
2.5
(63.5)
2.16
(54.9)
1.00
(25.4)
0.62
(15.7)
4.5
(114.3)
0.20 (5.08) Dia.
800 through 1200 Amps
Part No.
Rated
Current/Output
Resistance
(Ωs at 25˚C) Torque Range
3020-01104-0 800A/50mV 0.0000625 32-35 ft-lbs (43.4-47.5Nm)
3020-01105-0 1000A/50mV 0.00005 32-35 ft-lbs (43.4-47.5Nm)
3020-01106-0 1200A/50mV 0.0000417 32-35 ft-lbs (43.4-47.5Nm)
8-32 Kelvin output screws (all shunts): 14-15 in-lbs (1.58-1.69Nm)
MECHANICAL SPECIFICATIONS (continued)