Motors, Petrol Engines & Electrical Spare Parts

Compressor Motors, Engines & Electrical Spares

Electric motors, petrol engines and electrical control components are critical to reliable compressor operation. Replacement parts should be selected from the full electrical and mechanical specification rather than by appearance or power rating alone.

Compressed Air Systems UK supplies electric motors, Honda petrol engines, capacitors, overload switches and compatible engine service parts for selected compressor, pump and industrial machinery applications.

Before Ordering a Replacement Electric Motor

A replacement compressor motor needs to match both the electrical requirements and the mechanical arrangement of the original machine.

Single-Phase & Three-Phase Motors

Single-phase compressor motors are commonly used on smaller machines operating from a 230 V supply. Depending on the motor design, they may use a start capacitor, run capacitor or both.

Three-phase motors are commonly used on larger industrial compressors. A single-phase motor cannot normally be exchanged directly with a three-phase motor, or vice versa, without considering the electrical supply and control system.

Motor Speed & Pulley Ratio

Compressor pumps are designed to operate within a specified speed range. The motor speed and pulley arrangement determine pump speed, so changing either can affect airflow, temperature, current draw and component life.

Do not assume that a motor with the correct kW rating is suitable if its speed, frame, shaft or pulley arrangement differs from the original.

Choosing a Replacement Petrol Engine

Petrol engines used on compressors, generators, pumps and industrial machinery should be matched mechanically as well as by nominal power.

• Engine manufacturer and exact model code
• Rated power in HP or kW
• Recoil or electric-start arrangement
• Crankshaft diameter, usable length and keyway
• Shaft rotation and operating speed
• Base mounting-hole arrangement
• Pulley, coupling or clutch compatibility
• Overall dimensions and installation clearance

Do not select a petrol engine by horsepower alone. Engines with similar outputs can use different shafts, mounting patterns, controls and starting arrangements.

Capacitors, Overloads & Motor Protection

Start & Run Capacitors

Single-phase compressor motors may use a start capacitor, run capacitor or both depending on their design. Start and run capacitors perform different functions and are not interchangeable.

Match the original capacitor by:

• Capacitance value in microfarads
• Voltage rating
• Start or run duty
• Terminal arrangement
• Physical dimensions and mounting style

Overload Switches

An overload device is used to help protect a motor against sustained overcurrent and overheating. It should be matched to the motor full-load current and the compressor control arrangement.

Diagnose the Fault Before Replacing Electrical Parts

A compressor that will not start or repeatedly trips an overload does not necessarily have a failed motor. The cause should be investigated before replacement components are fitted.

Possible causes can include:

• Low or unstable supply voltage
• Incorrect electrical connection
• A failed start or run capacitor
• Incorrect overload setting
• Excessive compressor load
• Incorrect pulley ratio
• Failed unloading or non-return valve operation
• Tight bearings or mechanical seizure
• Poor cooling or ventilation
• Motor winding damage

Repeated breaker trips should not be addressed by simply fitting a larger protective device. Motor current, cable size, starting method, supply voltage and compressor condition should be checked first.

Information Needed to Identify the Correct Part

Providing accurate equipment information makes it much easier to identify a suitable replacement component.

• Compressor manufacturer, model and serial number
• Motor manufacturer and a clear photograph of the data plate
• Power, voltage, phase, current and motor speed
• Frame size and mounting arrangement
• Shaft diameter, length and keyway
• Existing capacitor or overload markings
• Petrol-engine model code, shaft dimensions and starting method
• A description of the fault or reason for replacement