Fast Response 5D 511k Zinc Oxide Varistor High Peak Current Withstand Capability

OEM Fast Response 5D 511k Metal Oxide Varistor High Peak Current Withstand Capability​
 

The most common modern type of varistor is the metal oxide varistor (MOV). Ceramic blocks of this type containing particles of zinc oxide, in a matrix of other metal oxides, such as small amounts of bismuth, cobalt, manganese oxides, are sandwiched between two metal plates to form the electrodes of the device. The boundaries between each die and adjacent elements form diode junctions, which allow current to flow in only one direction. The accumulation of randomly oriented grains is electrically equivalent to a network of back-to-back diode pairs, each in parallel with many other pairs.
 

When a small voltage is applied across the electrodes, only the reverse leakage through the diode junction causes a tiny current to flow. When a large voltage is applied, the diode junction breaks down due to a combination of thermionic emission and electron tunneling, causing a large current to flow. The result of this behavior is a nonlinear current-voltage characteristic, where MOVs have high resistance at low voltages and low resistance at high voltages.
 

Electrical characteristics
 

Varistors remain non-conductive during normal operation. As a shunt mode device, varistors are often used to suppress line voltage surges when the voltage across them remains well below their "clamping voltage". Varistors can fail for two reasons.

Catastrophic failures have occurred due to unsuccessful attempts to limit very large surges caused by events such as lightning strikes, where the energy involved is many orders of magnitude higher than the varistor can handle. Subsequent current flow from the impact could melt, burn or even vaporize the varistor. This thermal runaway is due to the lack of uniformity at the junctions of individual grain boundaries, leading to the failure of the dominant current path under thermal stress when the energy in the transient pulse (usually measured in Joules) is too high (i.e. significantly exceeds the fabrication quotient of the "Absolute Maximum Ratings"). The potential for catastrophic failure can be reduced by overrating or using specially selected MOVs in parallel.

Cumulative degradation occurs as more surges occur. For historical reasons, many MOVs have been misspecified, allowing frequent inflation that also reduces capacity. In this case, the varistor is not visibly damaged and outwardly appears to be functioning (no catastrophic failure), but it no longer provides protection. Eventually, it goes into a short circuit as the energy discharge creates a conductive path through the oxide.

The main parameter affecting the lifetime of a varistor is its energy (joule) rating. Increasing the energy level increases the number (of a defined maximum size) of transient pulses it can accommodate exponentially as well as the cumulative energy sum from clamped smaller pulses. When these pulses occur, the "clamping voltage" it provides during each event decreases, and a varistor is generally considered functionally degraded when its "clamping voltage" changes by 10%. Manufacturer's life expectancy charts involve current, severity, and number of transients for failure prediction based on the total energy dissipated over the life of the part.

In consumer electronics, especially surge protectors, the MOV varistors used are small enough that they will eventually fail. Other applications, such as power transmission, use VDRs of different structures in multiple configurations, designed for long life.

Characteristics of varistors

(1) Advantages: the voltage range is very wide, from several volts to several thousand volts, the surge current can be from tens to several thousand amperes, the response speed is fast, there is no polarity, no freewheeling, and the peak current withstand capacity is large. low price.
(2) Disadvantages: The clamping voltage is relatively high, which can generally reach 2 to 3 times the working voltage. In addition, pressure
The leakage current of the varistor increases with the increase of the number of surge impacts. The response time is longer and the parasitic capacitance is larger.
(3) Applicable occasions: DC power lines, low-frequency signal lines, or used in series with gas discharge tubes for AC power lines.

Specifications:

 

Part Number	Vac(V)	Vdc(V)	V1mA(V)	Ip(A)	Vc(V)	I(A)Standard	I(A)High Surge	(J)Standard	(J)High Surge	Rated power(W)	C@1KHz(pf)
10D180K(J)	11	14	18(15-21.6)	5	36	500	1000	2.1	3.0	0.05	5600
10D220K(J)	14	18	22(19.5-26)	5	43	500	1000	2.5	5.0	0.05	4500
10D270K(J)	17	22	27(14-31)	5	53	500	1000	3.0	6.0	0.05	3700
10D330K(J)	20	26	33(29.5-36.5)	5	65	500	1000	4.0	7.0	0.05	3000
10D390K(J)	25	31	39(35-43)	5	77	500	1000	4.6	9.0	0.05	2400
10D470K(J)	30	38	47(42-52)	5	93	500	1000	5.5	11	0.05	2100
10D560K(J)	35	45	56(50-62)	5	110	500	1000	7.0	13	0.05	1800
10D680K(J)	40	56	68(61-75)	5	135	500	1000	8.2	15	0.05	1500
10D820K(J)	50	65	82(74-90)	25	135	2500	3500	12	17	0.4	1200
10D101K(J)	60	85	100(90-110)	25	165	2500	3500	15	18	0.4	1000
10D121K(J)	75	100	120(108-132)	25	200	2500	3500	18	21	0.4	830
10D151K(J)	95	125	150(135-165)	25	250	2500	3500	22	25	0.4	670
10D181K(J)	115	150	180(162-198)	25	300	2500	3500	27	30	0.4	560
10D201K(J)	130	170	200(180-220)	25	340	2500	3500	30	35	0.4	500
10D221K(J)	140	180	220(198-242)	25	360	2500	3500	32	39	0.4	450
10D241K(J)	150	200	240(216-264)	25	395	2500	3500	35	42	0.4	420
10D271K(J)	175	225	270(243-297)	25	455	2500	3500	37	49	0.4	370
10D301K(J)	190	250	300(270-330)	25	500	2500	3500	40	54	0.4	330
10D331K(J)	210	275	330(297-363)	25	550	2500	3500	43	58	0.4	300
10D361K(J)	230	300	360(324-396)	25	595	2500	3500	47	65	0.4	280
10D391K(J)	250	320	390(351-429)	25	650	2500	3500	60	70	0.4	260
10D431K(J)	275	350	430(387-473)	25	710	2500	3500	65	80	0.4	230
10D471K(J)	300	385	470(423-517)	25	775	2500	3500	67	85	0.4	210
10D511K(J)	320	415	510(459-561)	25	845	2500	3500	69	90	0.4	200
10D561K(J)	350	460	560(504-616)	25	925	2500	3500	70	92	0.4	180
10D621K(J)	385	505	620(558-682)	25	1025	2500	3500	72	95	0.4	160
10D681K(J)	420	560	680(612-748)	25	1120	2500	3500	75	98	0.4	150
10D751K(J)	460	615	750(675-825)	25	1240	2500	3500	77	100	0.4	130
10D781K(J)	485	640	780(702-858)	25	1290	2500	3500	80	105	0.4	130
10D821K(J)	510	670	820(738-902)	25	1355	2500	3500	85	110	0.4	120
10D911K(J)	550	745	910(819-1001)	25	1500	2500	3500	93	130	0.4	110
10D102K(J)	625	825	1000(900-1100)	25	1650	2500	3500	102	140	0.4	100
10D112K(J)	680	895	1100(990-1210)	25	1815	2500	3500	115	155	0.4	90

 

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