Hammond Power Solutions HPS IMPERATOR Technical Data
SECTION 1
HPS IMPERATOR
SECTION 9
Recommendations For Overcurrent Protection
UL AND CSA (NORTH AMERICAN) STANDARDS
North American standards, including UL 508, National Electric Code 450 and the Canadian Electrical
Code Part I, require overcurrent protection on all control circuit transformers. There are two options for over-
current protection:
Option 1
Provide an overcurrent device in the primary circuit rated to the current of the transformer. The
overcurrent limits are as follows:
Primary 9 amps or more: no more than 125% of rated current.
Primary 2 to 9 amps: no more than 167% of rated current.
Primary less than 2 amps: no more than 300% of rated current for power circuits.
no more than 500% of rated current for control circuits.
This method is considered less desirable as start-up inrush to the transformer can frequently
surpass the current rating of the device and result in nuisance interruptions.
TM
SECTION 1
Option 2
The second option is to install overcurrent devices in both the primary and secondary circuits of the
transformer. In this option, the secondary device must be rated no more than 125% of rated current
of the transformer and the primary no more than 250%. CEC permits 300% overcurrent on the
primary for this option.
In both options listed, it is recommended that time delay fuses be considered to avoid unnecessary
interruptions.
Secondary
The overcurrent protection listed below, in amperes, is 125% of the rated current of the transformer. Choose
the next higher fuse rating if these numbers do not correspond with standard fuse selections.
Sec.
Voltage
12 2.7 5.3 7.9 11 16 21 27 - - - - - - - - -
24 1.4 2.7 4.0 5.3 7.9 11 14 16 19 27 - - - - - -
90 0.4 0.7 1.1 1.4 2.1 2.8 3.5 4.2 4.9 7.0 11 14 21 28 - -
95 0.4 0.7 1.0 1.4 2.0 2.7 3.3 4.0 4.7 6.6 9.9 14 20 27 - -
100 0.4 0.7 1.0 1.3 1.9 2.5 3.2 3.8 4.4 6.3 9.4 13 19 25 - -
110 0.3 0.6 0.9 1.2 1.8 2.3 2.9 3.5 4.0 5.7 8.6 12 18 23 - -
115 0.3 0.6 0.9 1.1 1.7 2.2 2.8 3.3 3.9 5.5 8.2 11 17 22 - -
120 0.3 0.6 0.8 1.1 1.6 2.1 2.7 3.2 3.7 5.3 7.9 11 16 21 - -
220 0.15 0.3 0.5 0.6 0.9 1.2 1.5 1.8 2.0 2.9 4.3 5.7 8.6 12 18 29
230 0.14 0.3 0.5 0.6 0.9 1.1 1.4 1.7 2.0 2.8 4.1 5.5 8.2 11 17 28
240 0.14 0.3 0.4 0.6 0.8 1.1 1.4 1.6 1.9 2.7 4.0 5.3 7.9 11 16 27
25 50 75 100 150 200 250 300 350 500 750 1000 1500 2000 3000 5000
VA Rating
© Hammond Power Solutions Inc.
47
Data subject to change without notice.
SECTION 1 HPS IMPERATOR
Recommendations for Overcurrent Protection continued...
Primary (UL and CSA)
To assist in the selection of fuses, the following chart recommends the maximum primary fuse rating in amperes.
The rst number shown is the maximum overcurrent protection when the primary current is less than 2 amps and the
overcurrent protection device is rated for 300%. The second number shown (italic) is recommended when the primary is
less than 2 amps and the overcurrent device is to be rated at 500% of rated current. Where only one number is indicated,
the primary is 2 amps or more and one rating of over current protection is shown as optimal. Choose the next higher fuse
rating if these numbers do not correspond with standard fuse selections.
Pri. VA Rating
Volt 25 50 75 100 150 200 250 300 350 500 750 1000 1500 2000 3000 5000 7500
115 0.6 1.25 1.8 2.5 3.5 5 4 5 5 8 10 15 20 25 - - -
SECTION 1
120 0.6 1.25 1.8 2.25 3.5 5 4 5 5 8 10 15 15 20 - - -
200 0.3 0.75 1.125 1.5 2.25 3 3.5 4.5 5 4.5 7 9 15 15 20 - -
208 0.3 0.6 1 1.4 2 2.8 3.5 4 5 4 6 8 12 15 20 30 -
220 0.3 0.6 1 1.25 2 2.5 3.2 4 4.5 4 6 8 12 15 20 30 -
230 0.3 0.6 0.8 1.25 1.8 2.5 3.2 3.5 4.5 4 6 8 10 15 20 30 -
240 0.3 0.6 0.8 1.25 1.8 2.25 3 3.5 4 3.5 5 7 10 15 15 30 -
277 0.25 0.5 0.8 1 1.6 2 2.5 3.2 3.5 5 5 6 9 12 15 25 -
347 0.25 0.5 0.8 1 1.6 2 2.5 3.2 3.5 5 6.25 5 7.5 10 15 20 30
380 0.1875 0.3 0.5 0.75 1.125 1.5 1.8 2.25 2.5 3.5 5.6 4.5 6.25 9 15 20 25
400 0.1875 0.3 0.5 0.75 1.125 1.5 1.8 2.25 2.5 3.5 5.6 4.5 6.25 9 12 15 20
416 0.15 0.3 0.5 0.6 1 1.4 1.8 2 2.5 3.5 5 4 6 8 12 15 20
440 0.15 0.3 0.5 0.6 1 1.25 1.6 2 2.25 3.2 5 4 6 8 12 15 20
460 0.15 0.3 0.4 0.6 0.8 1.25 1.6 1.8 2.25 3.2 4.5 3.5 6 8 12 15 20
480 0.15 0.3 0.4 0.6 0.8 1.25 1.5 1.8 2 3 4.5 3.5 5 7 10 15 20
550 0.125 0.25 0.4 0.5 0.8 1 1.25 1.6 1.8 2.5 4 5 4.5 6 9 15 15
575 0.125 0.25 0.3 0.5 0.75 1 1.25 1.5 1.8 2.5 3.5 5 4.5 6 9 15 15
600 0.125 0.2 0.3 0.5 0.75 0.8 1.25 1.5 1.6 2.25 3.5 5 4 6 9 15 15
1 2 3.2 4 6.25 8
1 2 3 4 6.25 8
0.6 1.25 1.8 2.5 3.5 5 6.25 7.5 8
0.6 1.125 1.8 2.25 3.5 4.5 6 7 8
0.5 1.125 1.6 2.25 3.2 4.5 5.6 6.25 7.5
0.5 1 1.6 2 3.2 4 5 6.25 7.5
0.5 1 1.5 2 3 4 5 6.25 7
0.4 0.8 1.25 1.8 1.5 3.5 4.5 5 6.25 9
0.4 0.8 1.25 1.8 2.5 3.5 4.5 5 6.25 9
0.3 0.6 0.8 1.25 1.8 2.5 3.2 3.5 4.5 6.25 9
0.3 0.6 0.8 1.25 1.8 2.5 3 3.5 4 6.25 9
0.3 0.6 0.8 1.125 1.8 2.25 3 3.5 4 6 9
0.25 0.5 0.8 1.125 1.6 2.25 2.8 3.2 3.5 5.6 8
0.25 0.5 0.8 1 1.6 2 2.5
0.25 0.5 0.75 1 1.5 2 2.5 3 3.5 5 7.5
0.2 0.4 0.6 0.8 1.25 1.8 2.25 2.5 3 4.5 6.25
0.2 0.4 0.6 0.8 1.25 1.6 2 2.5 3 4 6.25
0.2 0.4 0.6 0.8 1.25 1.6 2 2.5 2.8 4 6.25
3.2 3.5 5 8
TM
References:
© Hammond Power Solutions Inc.
UL 508, 32.7
UL 845, 11.16 and 11.17
NEC 430-72 (c) exception #2
NEC 450-3 (b) 1 and 2
CEC Part I, 26-256
48
Data subject to change without notice.
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