Magnetic Contactor Wiring Guide Pakistan | CNC Electric

Magnetic Contactor Wiring Guide Pakistan — Connection Diagram, Types & Prices 2026

Updated April 2026  |  By CNC Electric Pakistan  |  14 min read

If you run motors in Pakistan—whether it is a 1 HP water pump in Lahore, a 20 HP compressor in Faisalabad, or a 100 HP conveyor line in Port Qasim—the magnetic contactor is the single most important switching device in your control panel. It turns the motor on and off thousands of times without wearing out, protects downstream equipment, and enables automation when paired with timers, overload relays, and PLCs.

This guide covers everything Pakistani electricians, panel builders, and plant engineers need to know: what a contactor is, how it works internally, the full CNC CJX2 range with 2026 prices in Pakistani Rupees, step-by-step wiring diagrams for DOL and star-delta starters, contactor-timer combinations, selection criteria, and the wiring mistakes that cause most contactor failures in Pakistan.

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What Is a Magnetic Contactor?

A magnetic contactor is an electrically controlled switch designed to handle high-current loads—primarily motors. Unlike a manual switch or a simple relay, a contactor uses an electromagnetic coil to pull a set of heavy-duty contacts closed. When the coil is de-energised, a spring pushes the contacts open again.

Key characteristics that define a contactor:

• High current rating: Contactors are rated from 9 A to 800 A or more. The CNC CJX2 series covers 9 A to 160 A, which handles motors up to roughly 90 kW (120 HP).
• AC-3 duty: Contactors intended for motor starting are rated under the AC-3 utilisation category, which accounts for the 6–8× inrush current during motor start-up.
• Auxiliary contacts: Built-in NO (normally open) and NC (normally closed) auxiliary contacts allow the contactor to signal other devices—indicator lamps, PLCs, interlocks.
• Coil voltage options: Available in 220 V AC (most common in Pakistan), 380 V AC, 24 V DC, and 110 V AC.
• Millions of operations: A quality contactor like the CJX2 is rated for 1–3 million mechanical operations, far exceeding any manual switch.

In short, every time you press a “START” button on a motor control panel in Pakistan, it is a magnetic contactor that does the heavy lifting.

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How Does a Magnetic Contactor Work?

Understanding the internal mechanism helps you wire and troubleshoot contactors correctly. Here is the step-by-step sequence:

1. Coil energises: When control voltage (typically 220 V AC in Pakistan) is applied to terminals A1 and A2, current flows through the electromagnetic coil wound around a laminated iron core.
2. Magnetic field forms: The coil creates a strong magnetic field that pulls the movable iron armature downward against spring pressure.
3. Main contacts close: The armature is mechanically linked to the main power contacts (L1-T1, L2-T2, L3-T3). As it moves down, these contacts close, completing the power circuit to the motor.
4. Auxiliary contacts change state: Simultaneously, the NO auxiliary contact closes (used for the self-holding circuit) and the NC auxiliary contact opens (used for interlocks or indicator lamps).
5. Motor runs: Three-phase power flows through the closed contacts to the motor.
6. Coil de-energises: When the STOP button is pressed (or the overload relay trips), the coil loses power. The spring pushes the armature back up, opening all main and auxiliary contacts. The motor stops.

The entire sequence—from pressing START to full motor current flow—takes approximately 20–40 milliseconds. This fast, repeatable switching is why contactors are the backbone of industrial motor control worldwide.

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Contactor vs Relay — What Is the Difference?

Pakistani electricians often confuse contactors with relays. While both use electromagnetic coils to switch contacts, they serve very different purposes. Here is a side-by-side comparison:

Feature	Magnetic Contactor	Relay
Current Rating	9 A to 800 A+	1 A to 16 A typically
Primary Use	Motor switching, power circuits	Signal switching, logic control
Contact Type	3-pole main + auxiliaries	Multiple changeover (DPDT, 4PDT)
Arc Suppression	Built-in arc chutes	Minimal or none
Physical Size	Large (DIN-rail mount, 45–150 mm wide)	Compact (plug-in, 20–40 mm)
Overload Pairing	Mounts directly with thermal overload relay	Not applicable
Price (Pakistan)	Rs. 1,850 – Rs. 24,000	Rs. 350 – Rs. 1,500

Rule of thumb: If the load is a motor or any device drawing more than 10 A, use a contactor. If you are switching a control signal, an indicator lamp, or a PLC input, use a relay.

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CNC CJX2 Magnetic Contactor Range — Types & Prices in Pakistan (2026)

CNC Electric manufactures the CJX2 series of magnetic contactors—the most widely used contactor type in Pakistan, fully interchangeable with the Schneider LC1-D series. All models are IEC 60947-4-1 certified, rated for AC-3 motor duty, and available with 220 V AC coils as standard.

Model	AC-3 Rating	Motor kW (380V)	Typical Application	Price (PKR)
CJX2-1210	12 A	5.5 kW	Water pumps, small fans	Rs. 1,850
CJX2-1810	18 A	7.5 kW	Compressors, conveyor motors	Rs. 2,100
CJX2-2510	25 A	11 kW	15 HP motors, chillers	Rs. 2,500
CJX2-3210	32 A	15 kW	Industrial pumps, mixers	Rs. 3,200
CJX2-4011	40 A	18.5 kW	25 HP motors, crushers	Rs. 4,500
CJX2-5011	50 A	22 kW	30 HP motors, HVAC systems	Rs. 5,800
CJX2-6511	65 A	30 kW	40 HP motors, large pumps	Rs. 7,200
CJX2-8011	80 A	37 kW	50 HP motors, heavy industry	Rs. 10,500
CJX2-9511	95 A	45 kW	60 HP motors, flour mills	Rs. 14,000
CJX2-D115	115 A	55 kW	75 HP motors, textile machines	Rs. 18,500
CJX2-D150	160 A	90 kW	120 HP motors, steel mills	Rs. 24,000

All prices include GST. Prices valid as of April 2026. Bulk/dealer pricing available. Browse the full CNC contactor range →

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Contactor Wiring Diagram — DOL Motor Starter (Direct Online)

The DOL (Direct On Line) starter is the simplest and most common motor starting method in Pakistan. It uses one magnetic contactor, one thermal overload relay, and one MCB (or MCCB for larger motors). Here is the complete wiring guide:

Components Required

• MCB / MCCB — upstream short-circuit protection (view CNC circuit breakers)
• Magnetic Contactor (CJX2) — main switching device (view CNC contactors)
• Thermal Overload Relay — motor overload protection
• START push button (NO) — green, momentary
• STOP push button (NC) — red, momentary
• Indicator lamp — optional, shows motor running status

Power Circuit Wiring (Main Circuit)

1. Connect 3-phase supply (R, Y, B) to the MCB input terminals.
2. Connect MCB output to contactor main terminals L1, L2, L3 (top side).
3. Connect contactor output terminals T1, T2, T3 (bottom side) to the thermal overload relay input.
4. Connect thermal overload relay output to the motor terminals U, V, W.

Control Circuit Wiring (220V AC)

1. Take one phase (R) from the MCB output — this is your control supply live wire.
2. Connect it to the STOP button (NC) terminal 1.
3. From STOP button terminal 2, connect to the START button (NO) terminal 1.
4. From START button terminal 2, connect to the contactor coil terminal A1.
5. Self-holding circuit: Connect the contactor’s NO auxiliary contact (terminal 13) in parallel with the START button — wire from STOP button terminal 2 to auxiliary terminal 13, and from auxiliary terminal 14 to coil terminal A1.
6. Connect coil terminal A2 to Neutral (N) through the thermal overload relay’s NC contact (terminals 95-96).

How It Works

Press START → coil energises → main contacts close → motor runs. The NO auxiliary contact “seals in” the coil circuit, so the motor keeps running after you release the START button. Press STOP (or overload trips) → coil de-energises → contacts open → motor stops.

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Star-Delta Starter Wiring — For Motors Above 7.5 kW

For motors above 7.5 kW (10 HP), a DOL start draws excessive inrush current that can trip upstream breakers and cause voltage dips on the local grid. The star-delta starter solves this by starting the motor in star connection (reducing voltage to 58%) and then switching to delta after a timed interval.

Components Required

• 3 magnetic contactors: Main contactor (KM1), Star contactor (KM2), Delta contactor (KM3)
• Timer relay — adjustable 5–15 seconds (view CNC timers)
• Thermal overload relay
• MCCB for short-circuit protection
• Mechanical interlock between KM2 and KM3 (prevents simultaneous energisation)

Operating Sequence

1. Press START → KM1 (main) and KM2 (star) energise simultaneously.
2. Motor starts in star — draws only 33% of DOL current.
3. Timer counts down (typically 7–10 seconds for Pakistani 1450 RPM motors).
4. Timer expires → KM2 (star) de-energises → brief 50ms delay → KM3 (delta) energises.
5. Motor now runs in delta at full speed and full torque.

Important: Never energise KM2 and KM3 at the same time—this creates a dead short across phases. Always use a mechanical interlock and electrical interlock (NC contacts of each contactor in the other’s coil circuit).

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Contactor + Timer Combination — Automatic Motor Control

One of the most common applications in Pakistan is pairing a magnetic contactor with a timer relay for automatic on/off control. Typical uses include:

• Water tank filling: Timer runs pump for 30 minutes, then stops automatically.
• Exhaust fans: Timer runs ventilation fan for a set period after a selector switch is turned.
• Irrigation pumps: Timer cycles pump on/off for scheduled watering.
• Lighting control: Contactor switches high-current lighting loads via timer.

Wiring Method

Connect the timer’s NO output contact in series with the contactor coil circuit (between the START button and coil terminal A1). When the timer reaches its set time, the NO contact opens, de-energising the contactor and stopping the motor. The CNC AH2N timer (view here) is ideal for this application—DIN-rail mount, 0.1s to 60min range, and a rugged dial for adjustment.

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How to Select the Right Contactor Size — Motor kW to Contactor Amps

Undersizing a contactor is the most common mistake in Pakistani panels. Here is the correct selection process:

Step 1: Find Motor Full Load Current (FLC)

For a 3-phase motor at 380V:

FLC (Amps) = Motor kW × 1000 / (380 × 1.732 × Power Factor × Efficiency)

Simplified rule of thumb used in Pakistan: FLC ≈ Motor kW × 2 (at 380V, for standard efficiency motors).

Step 2: Select Contactor AC-3 Rating

Choose a contactor with an AC-3 rating equal to or greater than the motor FLC. Add a 25% safety margin for harsh environments (dusty factories, high ambient temperature).

Quick Selection Table

Motor Power	FLC (approx)	Recommended Contactor	Price (PKR)
1.5 kW (2 HP)	3.5 A	CJX2-1210 (12A)	Rs. 1,850
3.7 kW (5 HP)	7.5 A	CJX2-1210 (12A)	Rs. 1,850
5.5 kW (7.5 HP)	11 A	CJX2-1810 (18A)	Rs. 2,100
7.5 kW (10 HP)	15 A	CJX2-2510 (25A)	Rs. 2,500
11 kW (15 HP)	22 A	CJX2-3210 (32A)	Rs. 3,200
15 kW (20 HP)	30 A	CJX2-4011 (40A)	Rs. 4,500
22 kW (30 HP)	44 A	CJX2-6511 (65A)	Rs. 7,200
37 kW (50 HP)	74 A	CJX2-9511 (95A)	Rs. 14,000
55 kW (75 HP)	110 A	CJX2-D150 (160A)	Rs. 24,000

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Common Contactor Wiring Mistakes in Pakistan

After installing and servicing thousands of panels across Pakistan, these are the errors we see most frequently:

1. No self-holding circuit: Electricians connect the START button directly to the coil without using the NO auxiliary for latching. Result: motor runs only while the button is held down.
2. Missing overload relay in coil circuit: The thermal overload relay’s NC contact (95-96) must break the coil circuit, not just signal a lamp. Without this, the motor keeps running even when overloaded—leading to winding burnout.
3. Wrong coil voltage: Using a 380V coil contactor on a 220V control circuit (or vice versa). The coil either will not pull in or will burn out within hours.
4. Undersized contactor: Using a 12A contactor on a 15 HP motor because “it fits in the panel.” The contacts will weld shut within weeks.
5. No MCB/MCCB upstream: Relying on the contactor for short-circuit protection. Contactors do NOT provide short-circuit protection—that is the job of the MCB or MCCB.
6. Loose terminal connections: Pakistan’s vibrating gensets and poor cable termination cause loose contacts. Always use proper ferrules and torque terminals to spec.
7. No interlock in reversing/star-delta starters: Failing to electrically and mechanically interlock contactors that must never be ON simultaneously.
8. Using the contactor as an isolator: Switching the contactor on/off manually to isolate the motor. Use a proper isolator switch or selector switch upstream. A contactor is not an isolation device.

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Protect Your Motors and Panels — Related CNC Products

A magnetic contactor works best as part of a properly designed motor control panel. Here are the essential companion products:

• CNC Magnetic Contactors (CJX2 Series) — Full range 12A to 160A
• CNC Circuit Breakers (MCB & MCCB) — Short-circuit protection upstream of contactors
• CNC Timer Relays (AH2N) — For automatic motor on/off timing
• CNC Selector Switches — Manual/Auto mode selection for panels
• CNC Voltage Protectors — Protect motors from under/over voltage
• All CNC Industrial Products — Complete range for panel building

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Frequently Asked Questions (FAQs)

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