Current transformer 150/5A MSQ-30 ESS

ESS MSQ-30 150/5 A current transformer

⚡ The ESS MSQ-30 150/5 A is a measuring current transformer for connecting electricity meters, ammeters, network analysers and other instruments with a 5 A current input.

A power conductor or busbar passes through the central window. When the primary current reaches 150 A, the secondary terminals supply 5 A to the measuring device.

The transformation ratio is 30:1. The secondary reading must be multiplied by 30 unless the connected meter applies the ratio automatically.

✅ Main advantages

• 150 A rated primary current;
• standard 5 A secondary current;
• 150/5 current ratio;
• accuracy class 0.5;
• 5 VA rated burden;
• compact MSQ-30 enclosure;
• window-type construction;
• suitable for a busbar or power conductor;
• electrical isolation of the measuring circuit;
• suitable for single- and three-phase metering;
• compatible with transformer-operated meters with a 5 A input.

🔍 Understanding 150/5 A

• 150 A is the rated current in the power circuit;
• 5 A is the rated secondary current;
• 30 is the conversion multiplier.

For example, a secondary current of 3 A corresponds to an approximate primary current of 90 A: 3 × 30 = 90 A.

🎯 Accuracy class 0.5

Accuracy class 0.5 indicates suitability for relatively accurate metering when the rated burden and operating requirements are observed.

Accuracy is affected by secondary-circuit burden, wire length and size, terminal quality, current level, temperature and connection polarity.

🔋 Understanding the 5 VA burden

5 VA is the permitted total secondary-circuit burden at which the specified accuracy is maintained. It includes the meter current coil, connecting wires, terminals and any additional instruments.

Excessively long or undersized secondary wires increase resistance and may reduce measuring accuracy.

🏭 Applications

• transformer-operated three-phase electricity meters;
• electrical distribution panels;
• main distribution boards;
• ammeters;
• multifunction measuring instruments;
• power-network analysers;
• automated electricity-metering systems;
• commercial and industrial sites;
• load-monitoring systems;
• generator and solar-power installations.

🔩 MSQ-30 window-type construction

The primary winding is formed by the busbar or power conductor passing through the central opening.

The MSQ-30 series commonly uses a window suitable for an approximately 30 × 10 mm busbar. Confirm the actual opening and conductor dimensions before purchase.

🔌 Three-phase installation

A conventional three-phase metering arrangement normally requires three identical current transformers, one for each phase.

• one CT on phase L1;
• one CT on phase L2;
• one CT on phase L3;
• secondary terminals connected to the corresponding meter inputs;
• all three CTs must have the same ratio.

The P1/P2 primary direction and S1/S2 secondary polarity must be observed according to the wiring diagram.

⚠️ Critical safety rule

Never open the secondary circuit while primary current is flowing.

An open secondary circuit may generate a dangerous voltage, causing electric shock, insulation failure, overheating, transformer damage and subsequent measuring errors.

Before disconnecting a meter or instrument, safely short the CT secondary terminals through an appropriate test terminal block.

🛠️ Installation requirements

• installation must be performed by a qualified electrician;
• the power installation must first be isolated;
• select the CT according to maximum operating current;
• the busbar or conductor must fit freely through the window;
• observe the P1–P2 direction;
• do not interchange S1 and S2;
• use secondary wires of adequate cross-section;
• tighten all terminals securely;
• earth one secondary terminal when required by the design;
• enter the 150/5 ratio in the electricity meter settings.

🛡️ IP20 protection

IP20 protects against finger contact and solid objects larger than 12.5 mm, but provides no rated water protection.

The transformer should be installed inside a closed electrical panel protected from moisture and accidental access.

📦 Package contents

• MSQ-30 150/5 A current transformer;
• factory box;
• mounting components;
• passport;
• certificate.

📌 Summary

The ESS MSQ-30 150/5 A allows a meter or measuring instrument with a 5 A input to be safely connected to a circuit carrying up to 150 A. Accuracy class 0.5 and a 5 VA burden make it suitable for accurate technical and commercial metering when correctly designed and installed.