MSQ current transformers provide a window for a busbar or insulated primary conductor and a wound secondary for current measurement. Six frame sizes cover the ratio and burden combinations below. Select the current ratio, accuracy class, available VA and opening geometry together; a common frame size does not mean that every ratio has the same burden rating.
The construction uses an insulated magnetic core with a wound secondary and a moulded enclosure. Terminal covers and busbar or panel mounting accessories are shown in the assembly illustration. A dash in a burden column means that no rating is listed for that class and ratio. T denotes the required primary turns in the marked options.
Terminal cover, busbar support and panel mounting arrangements.
MSQ-30 ratings
Model
Ratio (A)
Burden (VA)
Units per case
Class 0.5
Class 1.0
MSQ-30
30/5
—
1.5 (3T)
40
40/5
1.5 (2T)
50/5
2.5 (2T)
60/5
75/5
1.5
80/5
100/5
2.5
150/5
3.75
200/5
5
5
250/5
7.5
300/5
10
10
MSQ-30 frame, conductor opening and mounting dimensions.
MSQ-40 ratings
Model
Ratio (A)
Burden (VA)
Units per case
Class 0.5
Class 1.0
MSQ-40
100/5
1.5
1.5
40
150/5
2.5
200/5
2.5
5
250/5
5
300/5
400/5
10
500/5
MSQ-40 conductor window, enclosure and fixing dimensions.
MSQ-60 ratings
Model
Ratio (A)
Burden (VA)
Units per case
Class 0.5
Class 1.0
MSQ-60
300/5
2.5
5
30
400/5
5
10
500/5
600/5
750/5
800/5
7.5
1000/5
10
15
1200/5
1500/5
15
1600/5
MSQ-60 enclosure and conductor-window dimensions.
MSQ-85 ratings
Model
Ratio (A)
Burden (VA)
Units per case
Class 0.5
Class 1.0
MSQ-85
750/5
5
10
30
800/5
1000/5
7.5
1200/5
10
15
1500/5
1600/5
2000/5
15
MSQ-85 frame opening and mounting geometry.
MSQ-100 ratings
Model
Ratio (A)
Burden (VA)
Units per case
Class 0.5
Class 1.0
MSQ-100
800/5
5
5
16
1000/5
10
10
1200/5
15
1250/5
1500/5
1600/5
2000/5
2500/5
3000/5
MSQ-100 body, opening and fixing dimensions.
MSQ-125 ratings
Model
Ratio (A)
Burden (VA)
Units per case
Class 0.5
Class 1.0
MSQ-125
1000/5
5
10
20
1200/5
7.5
1250/5
10
15
1500/5
1600/5
15
20
2000/5
2500/5
3000/5
4000/5
5000/5
20
6000/5
MSQ-125 opening and mounting references for the largest listed frame.
Measurement and protection selection
Measuring and protection transformers have different overload requirements. The listed MSQ burden schedules use measurement classes 0.5 and 1.0. For a protection application, specify the required protection class and accuracy-limit factor separately; a 5P15 designation combines class 5P with an accuracy-limit factor of 15.
Protection class reference
Current ratio error (%)
Phase displacement
Composite error (%)
Minutes
Centiradians
5P
±1
±60
±1.8
5
10P
±3
—
—
10
Illustrative burden and class behaviour, showing the distinction between measuring and protection duties.
Primary turns and secondary connections
Primary turns change the effective current ratio. The illustrated example uses a 100/5A transformer with two primary passes to obtain a 50/5A effective ratio. Include the secondary cable burden in the total VA, together with the measuring instrument burden, and keep the total within the selected transformer rating.
Orient P1/K toward the supply and P2/L toward the load. Do not open the secondary circuit while primary current is flowing; use the appropriate shorting and isolation arrangement before disconnecting instruments. Make secondary and earth connections according to the installation circuit.
Primary-turn arrangement showing equivalent 50/5A measurement using a 100/5A transformer with two passes.Magnetic core, insulated winding and secondary terminal construction.
