TMOV25SP750M Littelfuse Inc, TMOV25SP750M Datasheet - Page 20

• Manufacturer Part Number: TMOV25SP750M
• Description: TMOV VARISTOR PB FREE 25S
• Manufacturer: Littelfuse Inc
• Series: iTMOV®r

Specifications of TMOV25SP750M

• Varistor Voltage: 1320V (1.32kV)
• Current-surge: 20kA
• Number Of Circuits: 1
• Maximum Ac Volts: 750VAC
• Energy: 670J
• Package / Case: Disc 25mm 3-Lead
• Suppressor Type: Varistor
• Peak Surge Current @ 8/20µs: 20000A
• Varistor Case: 25mm DISC
• Clamping Voltage Vc Max: 1950V
• Peak Energy (10/1000us): 670J
• Voltage Rating Vdc: 1320V
• Voltage Rating Vac: 750V
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Maximum Dc Volts: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Nominal Varistor Region of Operation
The varistor characteristic follows the equation:
I = kV
defines the degree of nonlinearity. Alpha is a figure of merit
and can be determined from the slope of the V-I curve or
calculated from the formula:
In this region the varistor is conducting and R
dominate over C, R
magnitude less than R
During conduction the varistor voltage remains relatively
constant for a change in current of several orders of mag-
nitude. In effect, the device resistance, R
response to current. This can be observed by examining
the static or dynamic resistance as a function of current.
The static resistance is defined by:
and the dynamic resistance by:
Plots of typical resistance values vs current (I) are given in
Figure 16A and 16B.
FIGURE 15. EQUIVALENT CIRCUIT AT VARISTOR CONDUCTION
FIGURE 16A. R
a
0.05
0.01
, where (k) is a constant and the exponent (
500
100
0.5
0.1
50
10
0
5
1
0 .
Z
R
1
X
X
=
=
=
=
X
dv
------
V
--- -
di
------------------------------ -
log
------------------------------ - for I
log
I
STATIC VARISTOR RESISTANCE FIGURE
log
=
(
(
ON
(
V
V
0
I
1
V
2
2
2
1 .
and R
OFF
⁄
⁄
⁄
⁄
PEAK CURRENT (A)
I
V
V
1
1
1
I
)
but remains larger than R
)
)
=
OFF
L
R
R
. R
X
X
2
⁄
⁄
1
X
I
1
becomes many orders of
=
1
X
, is changing in
10
X
will pre-
a
ON
)
.
Revision: November 5, 2009
1
Varistor Products
0
0
16
Upturn Region of Operation
At high currents, approaching the maximum rating, the
varistor approximates a short-circuit. The curve departs
from the nonlinear relation and approaches the value of the
material bulk resistance, about 1Ω-10Ω. The upturn takes
place as R
represents the bulk resistance of the Z
tance is linear (which appears as a steeper slope on the log
plot) and occurs at currents 50A to 50,000A, depending on
the varistor size.
FIGURE 17. EQUIVALENT CIRCUIT AT VARISTOR UPTURN
FIGURE 16B. Z
0.005
0.001
0
0.01
0.05
.
0.5
01
5
1
0.01
X
approaches the value of R
X
DYNAMIC VARISTOR RESISTANCE
0.1
Please refer to www.littelfuse.com for current information.
PEAK CURRENT (A)
Specifications are subject to change without notice.
L
R
ON
1.0
ON
N
. Resistor R
O grains. This resis-
10
©2009 Littelfuse, Inc.
ON
100