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© 2015 Eaton. All Rights Reserved..
1
Motor and Motor Circuit Protection
© 2015 Eaton. All Rights Reserved..
Motor and Motor Circuit Protection
• Agenda
• Motor Circuit Characteristics
• Protection from Overcurrents
• Motor Circuit Requirements
• Sizing OCPD’s
• Back-up Overload Protection
• Type 2 Protection
© 2015 Eaton. All Rights Reserved..
3
Motor and Motor Circuit Protection
• How does a motor operate?
• Starting
• Normally
• What do we protect against?
• Overload
• Short-Circuit
© 2015 Eaton. All Rights Reserved..
4
1000
Normal
Operating
Current
Time in Seconds
100
10
Motor Inrush
Curve
1
Inrush
Current
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
5
1000
Time in Seconds
100
10
300 %
Overload
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
6
1000
Time in Seconds
100
10
Short
Circuit
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
7
Motor Circuit Requirements(NEC®)
To Supply
• 430.101- 430.113 (Part IX)
• Disconnecting means
• 430.52
Motor
• Branch-Circuit Short-Circuit Protection
• 430.32
Branch
Motor
• Overload Protection
Overload
M
© 2015 Eaton. All Rights Reserved..
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Motor and Motor Circuit Protection
• NEC® 430.102
• Location(Of Disconnecting Means)
• (A) In sight from Controller
• Branch-Circuit Short-Circuit Disconnect
• (B) In sight from Motor
• Branch-Circuit Short-Circuit Disconnect
• Manual Motor Controller “Suitable as Motor
Disconnect”
• Exceptions provided if (A) is lockable in open position.
© 2015 Eaton. All Rights Reserved..
9
1999 NEC® Code
Barrier, wall or isle
with an obstruction
Lockable
Disconnecting
Means
Controller
M
© 2015 Eaton. All Rights Reserved..
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Requirement since 2002 NEC® Code
In sight (of controller)
disconnecting means
ahead of controller
required per
430.102(A)
Barrier, wall or isle
with an obstruction
In sight motor
disconnecting means
required per 430.102(B)
Controller
M
© 2015 Eaton. All Rights Reserved..
11
Motor and Motor Circuit Protection
• NEC® 430.52
• Branch-Circuit Short-Circuit Protection
• (B) Must handle starting current
• (C) Rating or Setting
• (1) Table 430.52
• Exception 1: Next Higher size is permitted if the values
from table 430.52 do not correspond to a standard
size
© 2015 Eaton. All Rights Reserved..
12
Motor and Motor Circuit Protection
• Table 430.52 Maximum Rating*
Non timedelay
Fuse1
Dual-Element
(Time-Delay) Fuse
Instantaneous Trip
Breaker
Inverse
Time
Breaker
300%
175%
800%
250%
1Non-Time-Delay also applies to Class CC fuses
*Single-phase motors, AC polyphase motors other than wound-rotor,
squirrel cage-other than Design B energy-efficient
© 2015 Eaton. All Rights Reserved..
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Motor and Motor Circuit Protection
• NEC® 430.52(C)(1) Exception 2:
• If Motor Unable to Start, then size according to following,
or next smaller size
Non timeDual-Element
delay
(Time-Delay) Fuse
1
Fuse
400%
1Non-Time-Delay
Inverse
Time
Breaker>
Inverse
Time
Breaker<
100A
100A
300%
400%
225%
6016000A
Fuse
300%
also applies to Class CC fuses
© 2015 Eaton. All Rights Reserved..
14
Motor and Motor Circuit Protection
• NEC® 430.32 (Overload Protection)
• (a) More than 1 Horsepower.
• (1) A separate overload device that is responsive to
motor current. This device shall be selected to trip or
rated at no more than the following percent of the motor
nameplate full-load current rating.



Motors with a marked service factor 1.15 or greater 125%
Motors with a marked temperature rise 40 °C or less 125%
All other motors
115%
© 2015 Eaton. All Rights Reserved..
15
MOTOR CIRCUIT DEVICES
© 2015 Eaton. All Rights Reserved..
Motor and Motor Circuit Protection
• What OCPD(s) can be
used in a motor circuit?
• Fuse
• Circuit Breaker
• MCP
• Overload relay
© 2015 Eaton. All Rights Reserved..
17
1000
Time in Seconds
100
10
Motor Inrush
Curve
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
18
1000
MCP at
minimum
setting
Time in Seconds
100
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
19
1000
MCP at
minimum
setting
Time in Seconds
100
10
Motor Inrush
Curve
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
20
1000
MCP at
maximum
setting
Time in Seconds
100
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
21
1000
MCP at
maximum
setting
Time in Seconds
100
10
Motor Inrush
Curve
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
22
1000
Time in Seconds
100
10
300 %
Overload
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
23
1000
Time in Seconds
100
Motor
Damage
Curve
10
1
0.1
0.01
1
10
100
1000
Current in Amperes
© 2015 Eaton. All Rights Reserved..
24
1000
Time in Seconds
100
Motor
Damage
Curve
300 %
Overload
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
25
1000
MCP at
maximum
setting
Motor
Damage
Curve
300 %
Overload
Time in Seconds
100
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
26
1000
15A Circuit
Breaker
Time in Seconds
100
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
27
1000
15A Circuit
Breaker
Time in Seconds
100
10
Motor Inrush
Curve
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
28
1000
15A Circuit
Breaker
Time in Seconds
100
Motor
Damage
Curve
300 %
Overload
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
29
1000
NON-2 Amp
Time in Seconds
100
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
30
1000
NON-2 Amp
Time in Seconds
100
10
Motor Inrush
Curve
1
0.1
0.01
1
10
100
1000
Current in Amperes
© 2015 Eaton. All Rights Reserved..
31
1000
NON-5 Amp
Time in Seconds
100
10
1
0.1
0.01
1
10
100
1000
Current in Amperes
© 2015 Eaton. All Rights Reserved..
32
1000
NON-5 Amp
Time in Seconds
100
10
Motor Inrush
Curve
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
33
1000
NON-5 Amp
Time in Seconds
100
Motor
Damage
Curve
300 %
Overload
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
34
1000
Time in Seconds
100
10
1
Overload
Relay
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
35
1000
Time in Seconds
100
10
Motor Inrush
Curve
1
Overload
Relay
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
36
1000
Time in Seconds
100
1
Motor
Damage
Curve
300 %
Overload
0.1
Overload
Relay
10
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
37
1000
MCP at
maximum
setting
Motor
Damage
Curve
300 %
Overload
Time in Seconds
100
10
1
Overload
Relay
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
38
1000
15A Circuit
Breaker
Time in Seconds
100
1
Motor
Damage
Curve
300 %
Overload
0.1
Overload
Relay
10
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
39
1000
NON-5 Amp
Time in Seconds
100
1
Motor
Damage
Curve
300 %
Overload
0.1
Overload
Relay
10
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
40
1000
FRN-R-1-6/10
Time in Seconds
100
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
41
1000
FRN-R-1-6/10
Time in Seconds
100
10
Motor Inrush
Curve
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
42
1000
FRN-R-1-6/10
Time in Seconds
100
Motor
Damage
Curve
300 %
Overload
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
43
Motor and Motor Circuit Protection
• Optimal Branch Circuit Protection (Back-up Overload
Protection):
• 125% or up of FLA - FRN/FRS
• 130% or up of FLA- LPN/LPS
• 150% or up of FLA- LPJ
• 200% or up of FLA- LP-CC
© 2015 Eaton. All Rights Reserved..
44
1000
FRN-R-1-8/10
Time in Seconds
100
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
45
1000
FRN-R-1-8/10
Time in Seconds
100
Motor
Damage
Curve
10
1
Overload
Relay
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
46
1000
FRN-R-1-8/10
Time in Seconds
100
1
Motor
Damage
Curve
300 %
Overload
0.1
Overload
Relay
10
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
47
Single-Phasing
• Single phasing is the opening of one phase of
a three phase circuit.
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48
Primary Single Phasing
• Primary wire broken by:
• Storm - Wind - Ice - Sleet - Hail - Lightning
• Vehicle or Plane Striking Pole
• Falling Tree Limbs
• Construction Mishaps
• Primary wire burned out from short-circuit
created by animals(i.e. squirrel to ground)
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49
Primary Single Phasing
• Defective contacts on primary breaker - failure
to make up on all 3 poles.
• Failure of 3 shot automatic reclosers to make
up on all 3 poles.
• Open pole on 3Ø auto. voltage tap changer
• Open winding in one phase of transformer
• Primary fuse open
© 2015 Eaton. All Rights Reserved..
50
Primary Single Phasing
Normal Condition
1.4 A
1.4 A
M
1.4 A
208V 1/3 HP Motor
40 C
F.L.A. = 1.4 Amperes
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51
Primary Single Phasing
Single Phase Condition
Assume one phase lost on the primary side of transformer.
1.61 A
3.22 A
(115%)
(230%)
1.61 A
208V 1/3 HP Motor
M
(115%)
40 C
F.L.A. = 1.4 Amperes
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52
Secondary Single Phasing
• Damaged Motor Starter Contact - One Pole
Open
• Burned open overload relay (heater)
• Damaged switch or circuit breaker on the
main, feeder, or branch circuit.
• Open fuse or open pole in breaker on main,
feeder, or branch circuit.
• Open cable or bus on secondary of
transformer terminals
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53
Secondary Single Phasing
• Open cable caused by overheated lug on
secondary side-connection to service head.
• Open connection in wiring such as in motor
junction box (caused by vibration) or any pull
box
• Open winding in motor
• Open winding in one phase of transformer
winding
© 2015 Eaton. All Rights Reserved..
54
Secondary Single Phasing
Normal Condition
1.4 A
1.4 A
M
1.4 A
208V 1/3 HP Motor
40 C
F.L.A. = 1.4 Amperes
© 2015 Eaton. All Rights Reserved..
55
Secondary Single Phasing
Single Phase Condition
Contacts on one phase are worn out resulting in an open circuit
0A
2.4 A
(173%)
2.4 A
208V 1/3 HP Motor
M
(173%)
40 C
F.L.A. = 1.4 Amperes
© 2015 Eaton. All Rights Reserved..
56
1000
FRN-R-1-6/10
Time in Seconds
100
Motor
Damage
Curve
Secondary
Single
Phasing
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
57
1000
FRN-R-1-8/10
Time in Seconds
100
Motor
Damage
Curve
Secondary
Single
Phasing
Overload
Relay
10
1
0.1
0.01
1
10
100
Current in Amperes
© 2015 Eaton. All Rights Reserved..
1000
58
What about short circuit protection for a motor
circuit?
© 2015 Eaton. All Rights Reserved..
Motor and Motor Circuit Protection
Current
Source
M
• Short Circuit Condition
© 2015 Eaton. All Rights Reserved..
60
If the overcurrent protective devices
are sized according to the
maximums in NEC® 430.52, will the
motor circuit components be
protected from damage?
© 2015 Eaton. All Rights Reserved..
TYPE 1 PROTECTION vs. TYPE 2
PROTECTION
© 2015 Eaton. All Rights Reserved..
TYPE 1 vs. TYPE 2 PROTECTION
• What is Type 1 and Type 2 Protection?
• IEC 947-4-1 Standard
• Type 1 Protection(Damage)
• UL 508 Listing
• Type 2 Protection(No Damage)
• Type 2 Tables from Manufacturer
© 2015 Eaton. All Rights Reserved..
63
TYPE 1 vs. TYPE 2 PROTECTION
• Type 1 Protection:
•
“Requires that, under short-circuit conditions, the
contactor or starter shall cause no danger to
persons or installation and may not be suitable for
further service without repair and replacement of
parts.”
• Similar to UL 508 requirements
© 2015 Eaton. All Rights Reserved..
64
TYPE 1 vs. TYPE 2 PROTECTION
• Type 2 Protection:
• “Requires that, under short-circuit conditions, the
contactor or starter shall cause no danger to
persons or installation and shall be suitable for
further use. The risk of contact welding is
recognized, in which case the manufacturer shall
indicate the measure to be taken as regards the
maintenance of the equipment.”
© 2015 Eaton. All Rights Reserved..
65
Type 2 Protection Tables
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66
TYPE 1 vs. TYPE 2 PROTECTION
• Does NEC® require Type 2 protection?
© 2015 Eaton. All Rights Reserved..
67
TYPE 1 vs. TYPE 2 PROTECTION
• NEC® section 110.10: Circuit Impedance, ShortCircuit Current Ratings, and Other Characteristics.
The overcurrent protective devices, the total
impedance, the equipment short-circuit current ratings,
and other characteristics of the circuit to be protected
shall be selected and coordinated to permit the circuitprotective devices used to clear a fault to do so
without extensive damage to the electrical equipment
of the circuit……Listed equipment applied in
accordance with their listing shall be considered to
meet the requirements of this section.
© 2015 Eaton. All Rights Reserved..
68
TYPE 2 PROTECTION
• Why Is Total Protection Important?
• Maximum Safety To Personnel And Equipment
• Minimum Cost To Stay In Service
• Maximum Productivity From The Equipment
© 2015 Eaton. All Rights Reserved..
69
Motor and Motor Circuit Protection
• Overload Protection
• Overload Relay
• Fuses for Backup
• Short Circuit Protection
• Fuse, Circuit Breaker, MCP
• Type 2 Protection(No Damage)
© 2015 Eaton. All Rights Reserved..
70
© 2015 Eaton. All Rights Reserved..
71