MEGAOHMTM Series

For New Technology Network
Insulated Bearings
TM
R
corporation
MEGAOHM
Series
CAT. No. 3030／E
Insulated Bearings MEGAOHMTM Series :
Offering Enhanced Safety and Reliability
Bearings used in electrical equipment such as motors and power generators tend to exhibit electrical pitting as a
result of current leakage. NTN's MEGAOHMTM Series of insulated bearings has been specifically designed to
counteract electrical pitting. These bearings are available in both ceramic and resin types suited to a variety of
applications. The MEGAOHMTM Series of insulated bearings offers the following unique advantages:
¡Exhibits insulation resistance of at
least 100 MΩ at 500 VDC.
¡Available in a wide range of variants
with various insulating layer materials,
high voltage resistance and shock
immunity that accommodate diverse
user requirements.
¡Compatible with ISO 492, DIN 620 and
JIS 1514 standards.
¡Available in bore diameters ranging from
50 to 160 mm.
The Mechanism of Electrical Pitting
An electrical current present near a bearing can flow to the
inside of the bearing, causing sparks that damage the rolling
contact surface. This phenomenon is known as "electrical
pitting." When such sparks first occur, circular spots can
appear on the rolling contact surface (Photo 1). The thermal
effects of the sparks can cause the metallurgical composition
and hardness in this problematic area to differ from those of
the surrounding normal areas, resulting in a white layer,
hardened layer and tempered layer. As a result, the problematic
area can eventually develop flaking. Furthermore, if the
electrical pitting phenomenon progresses, a corrugation
pattern (Photo 2) can develop that increases running noise
and vibration. Consequently, the bearing can no longer
adequately function.
Photo 1
Photo 3
Hardened layer
White layer
Tempered layer
Photo 2
1
Fig. 1
Insulated Bearings
MEGAOHMTM Series
Specifications
Ceramic Insulated Bearings
Resin Insulated Bearings
Standard type
Bearing
steel
Insulating
layer
Protected type
Bearing
steel
Protecting
layer
Outer
ring
Outer
ring
Rolling
element
Rolling
element
Cage
Cage
Inner
ring
Inner
ring
Cylindrical
Roller Bearing
Deep Groove
Ball Bearing
Cylindrical
Roller Bearing
Deep Groove
Ball Bearing
Bearing Numbers
Ceramic insulated bearings
Resin insulated bearings
7MC3-6330M2C3
High voltage
resistance
7MP-NU214L1BC4P6
Clearance
Cage
Bore diameter
Dimension series
Bearing type
7MC: Protected ceramic layer type with high
voltage resistance
7MC2: Protected ceramic layer type
7MC3: Standard type
Tolerance
Clearance
Cage
7MC
7MC2
7MC3
7MP
7MP2
Bore diameter
Dimension series
Bearing type
7MP: Standard resin type
7MP2: Heat-dissipating and creep-resistant
resin type
：5kV
：3kV
：3kV
：5kV
：5kV
Note: The insulated bearings MEGAOHMTM Series includes a range of high-temperature models. For technical assistance, contact NTN Engineering.
Performance
The various features of the insulated bearings
MEGAOHMTM Series are summarized below.
Choose the configuration that best suits your
application.
Insulation performance
Creep resistance
Heat dissipation
Shock immunity
Price
Ceramic
Resin
Ceramic Rolling Element
(reference)
◎
◎
◎
○
○
◎
○
○
○
◎
◎
◎
◎
◎
△
◎：Excellent
○：Normal
△：Poor
2
Insulated Bearings
MEGAOHMTM Series
Dimension Tables for Ceramic Insulated Bearings
B2
B
B
r
r
r1
r
r1
φD
φd φd1
φd
NU Type
φD
NH Type
Cylindrical roller bearing
Bearing
types
Bearing numbers
Boundary dimensions
mm
Deep groove
ball bearing
Cylindrical roller bearing
d
D
B
rs min
Deep groove ball bearing
Basic load ratings
Dynamic
Static
N
Cr
N
Cor
d
d1
B1
B2
r1s min
Required
shoulder
height
mm
Da
max min
Collar
ring
numbers
Boundary dimensions
mm
7MC (n) -NU214
70 125
24
1.5
83 500
95 000
−
−
−
−
−
−
117 109
7MC (n) -NU314
70 150
35
2.1
158 000
168 000
−
−
−
−
−
−
139 126.5
7MC (n) -NU316
80 170
39
2.1
201 000
223 000
−
−
−
−
−
−
159 143.2
7MC (n) -NH318
90 190
43
3
240 000
265 000
HJ318
90 125
12
21
3
177 163.8
7MC (n) -NH320 100 215
47
3
299 000
335 000
HJ320
100 140.5
13
22.5
3
202 180.3
7MC (n) -NH322 110 240
50
3
360 000
400 000
HJ322
110 155.5
14
23
3
227 200.9
7MC (n) -NU326 130 280
58
4
560 000
665 000
−
−
−
−
−
−
264 235.9
7MC (n)-NU330
150 320
65
4
665 000
805 000
−
−
−
−
−
−
304 268.9
7MC (n) -6311
55 120
29
2
71 500
45 000
−
−
−
−
−
−
111 104.5
7MC (n) -6312
60 130
31
2.1
82 000
52 000
−
−
−
−
−
−
119 112.6
7MC (n) -6316
80 170
39
2.1
123 000
86 500
−
−
−
−
−
−
159 150.7
7MC (n) -6324
120 260
55
3
207 000
185 000
−
−
−
−
−
−
247 225.6
7MC (n) -6230
150 270
45
3
176 000
168 000
−
−
−
−
−
−
257 240.2
7MC (n) -6330
150 320
65
4
274 000
284 000
−
−
−
−
−
−
304 275.9
Notes : For bearing clearances and cage types, contact NTN Engineering.
The bearing numbers listed here refer to current products. For bearings with
other numbers, contact NTN Engineering.
7MC（n）
φd
※Required shoulder height
7MC: Protected ceramic layer type with high voltage resistance
7MC2: Protected ceramic layer type
7MC3: Standard type
φDa
3
Insulated Bearings
MEGAOHMTM Series
Dimension Tables for Resin Insulated Bearings
B
B
r
r
r
r1
φD
φd
φD
Cylindrical roller bearing
Bearing
types
Bearing numbers
φd
Deep groove ball bearing
N
Cor
Required
shoulder
height
mm
Da
max
Basic load ratings
Boundary dimensions
Dynamic
d
D
B
rs min
Cylindrical roller bearing
Static
N
Cr
7MP-NUP208
7MP-NUP210
7MP2-NU214
7MP2-NU314
7MP2-NU215
7MP-NU315 ※
7MP-NU316 ※
7MP2-NU217
7MP-NU1017 ※
7MP-NU219 ※
7MP-NU220 ※
40
50
70
70
75
75
80
85
85
95
100
80
90
125
150
130
160
170
150
130
170
180
18
20
24
35
25
37
39
28
22
32
34
1.1
1.1
1.5
2.1
1.5
2.1
2.1
2
1.1
2.1
2.1
43 500
48 000
83 500
158 000
166 000
190 000
201 000
126 000
74 500
166 000
183 000
43 000
51 000
95 000
168 000
195 000
205 000
223 000
149 000
95 500
195 000
217 000
73.5
83.5
117
139
122
149
159
141
123.5
159
169
Deep groove ball bearing
mm
7MP2-6310
7MP2-6311
7MP2-6312
7MP2-6314
7MP-6215
7MP-6316 ※
7MP2-6217
7MP-6318 ※
7MP-6219 ※
7MP-6319 ※
7MP-6320 ※
7MP-6322 ※
7MP-6030 ※
50
55
60
70
75
80
85
90
95
95
100
110
150
110
120
130
150
130
170
150
190
170
200
215
240
225
27
29
31
35
25
39
28
43
32
45
47
50
35
2
2
2.1
2.1
1.5
2.1
2
3
2.1
3
3
3
2.1
62 000
71 500
82 000
104 000
66 000
123 000
83 500
143 000
109 000
153 000
173 000
205 000
126 000
38 500
45 000
52 000
68 000
49 500
86 500
64 000
107 000
82 000
119 000
141 000
179 000
126 000
101
111
119
139
122
159
141
177
159
187
202
227
214
Notes : For bearing clearances and cage types, contact NTN Engineering.
The bearing numbers listed here refer to current products. For bearings with other numbers, contact NTN Engineering.
※Available only with a 7MP prefix.
4
Insulated Bearings
MEGAOHMTM Series
Typical Applications
Electric Motors
The insulated bearings MEGAOHMTM Series is widely used in the traction motors of railway cars.
The unique knowledge and experience NTN has gained from motor applications in railways- where safety is the No. 1
priority- have contributed to the greatly improved reliability of general-purpose motors.
Traction motors
Power Generators
The insulated bearings MEGAOHMTM Series is also used in wind power generation systems, which are one solution to energy
issues such as the prevention of global warming. These bearings contribute to the improved reliability of eco-friendly wind
power generation systems.
Generator unit
5
Insulated Bearings
MEGAOHMTM Series
Operating Precautions
To avoid an accident or failure resulting from damage to insulated bearings, carefully observe
the following.
• Never drop an insulated bearing or strike it directly with a hammer during
installation (Illustrations 1 and 2).
• Do not use an insulated bearing if a defect is visible on the surface
(Illustration 3) or it has an unusual appearance.
0.5 mm
minimum
10˚∼15˚
• Attaching an electrical conductor to an insulated bearing can lower the
bearing’s insulation resistance.
• To prevent current flow from the side faces of a bearing, strictly observe the
mounting dimensions given in the dimension tables for required shoulder
height.
• Providing approximately 15˚ of relief (illustrated at right) at the entrance to
the housing will facilitate assembly.
• For DC motors such as those used in railway cars, earth-ground the shaft
during a voltage resistance test.
Relief at entrance of housing bore
Excessive shock can damage the insulating layer, possibly resulting in electrical pitting. Electrical pitting can in turn
damage the bearing, leading to abnormal bearing performance and possible faulty operation or failure.
Illustration 1
Illustration 2
Illustration 3
6
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NOTE : The appearance and specifications may be changed without prior notice
if required to improve performance. Although care has been taken to
assure the accuracy of the data compiled in this catalog, NTN does not
assume any liability to any company or person for errors or omissions.
AE68 CAT. No. 3030/E 04. 04. 05. D
Printed in Japan