Knowledge of proper installation techniques is vital to the effective operation of a motor. The following are some of the important motor installation procedures that need to be considered.
Foundation
A rigid foundation is a must for optimal operation of a motor. It helps to reduce vibration and noise, which can extend the life of the motor and make it more comfortable to operate. A rigid foundation also helps to ensure that the motor is properly aligned with the load, which can improve efficiency and reduce wear and tear. Concrete is the best foundation material for motors, especially large motors and driven loads.
Mounting
Motors can be mounted in a variety of ways, depending on the application. Some common mounting methods include:
- Rigid mounting: This is the most common type of mounting and is used when the motor needs to be securely attached to the equipment. The motor is bolted, welded, or cast to the mounting surface.
- Resilient mounting: This type of mounting is used to absorb vibration and noise. The motor is mounted on rubber or other resilient material that helps to isolate it from the equipment.
- Face mounting: This type of mounting is used when the motor needs to be directly coupled to another piece of equipment. The motor has a machined face with a pilot that fits into a corresponding hole in the other piece of equipment.
- Foot mounting: This type of mounting is used when the motor needs to be mounted on a flat surface. The motor has feet that rest on the mounting surface.
- Hanging mounting: This type of mounting is used when the motor needs to be suspended from the ceiling or other overhead structure. The motor has a hanger that is attached to the mounting surface.
The best mounting method for a particular application will depend on a number of factors, such as the size and weight of the motor, the type of equipment it is being mounted to, and the vibration and noise requirements.
Here are some additional things to keep in mind when mounting a motor:
- Make sure that the mounting surface is level and strong enough to support the weight of the motor.
- Use the correct size and type of bolts to secure the motor to the mounting surface.
- Align the motor shaft with the shaft of the equipment it is being mounted to.
- Make sure that the motor is properly grounded.
Motor and Load Alignment
Misalignment between the motor shaft and the load shaft can cause unnecessary vibration and premature bearing failure. This is because the misalignment creates a force that acts on the bearings, causing them to wear out prematurely.
There are a number of different ways to align a motor and load. One common method is to use a laser alignment kit. This kit uses a laser beam to measure the misalignment between the two shafts. Once the misalignment is measured, it can be corrected by adjusting the position of the motor or load.
In some cases, it may also be necessary to place a shim (thin piece of metal) under the feet of the motor. This will help to level the motor and reduce the misalignment.
Proper alignment of the motor and load is essential for ensuring their longevity and reliability. By taking the time to align the motor and load properly, you can help to prevent premature bearing failure and other problems.
Direct-drive motors are a type of motor that transmits power directly from the motor shaft to the load shaft. This means that there are no gears or belts involved, which can lead to improved efficiency and reliability. Direct-drive motors are often used in applications where space is limited, such as in elevators and escalators.
Belt drives and gear drives are two types of mechanical couplings that can be used to transmit power from a motor to a load. Belt drives are typically used for applications where variable speeds are required, while gear drives are typically used for applications where a fixed speed is required.
Motor rpm / Equipment rpm = Equipment pulley diameter / Motor pulley diameter
Belt drives are a type of mechanical system that uses a belt to transmit power from a motor to a load. Belt drives are typically used in applications where variable speeds are required, such as in conveyors and fans.
- The belt in a belt drive is made of a flexible material, such as rubber or fabric. The belt is wrapped around two pulleys, called the drive pulley and the driven pulley. The drive pulley is connected to the motor, and the driven pulley is connected to the load.
- The belt is tensioned by a spring or a tensioner. The tension of the belt is important to ensure that the belt does not slip. If the belt is too loose, it will slip, and if the belt is too tight, it will wear out prematurely.
- The belt deflection is the amount of flexure in the belt. The belt deflection should be checked regularly to ensure that it is within the specified range. If the belt deflection is too great, it will cause the belt to wear out prematurely.
- Misalignment is one of the most common causes of premature belt failure. Misalignment occurs when the two pulleys are not in the same plane. There are two types of misalignment: angular misalignment and parallel misalignment.
- Angular misalignment occurs when the two pulleys are not parallel. Parallel misalignment occurs when the two pulleys are parallel but not in the same axis.
- Misalignment can cause the belt to slip, which can lead to premature wear and tear. To prevent misalignment, the two pulleys should be properly aligned.
Motor Bearings
Motor bearings are essential for the smooth operation of a motor. They support the motor shaft and prevent it from rubbing against the end bells.
There are two main types of motor bearings: sleeve bearings and ball bearings. Sleeve bearings are made of a single piece of metal and are lubricated with grease. Ball bearings are made of two or more balls that are held in place by a cage. Ball bearings are lubricated with oil.
Most motors today have sealed bearings. This means that the bearings are filled with lubricant and do not require periodic lubrication. However, it is still important to check the seals periodically to make sure they are not leaking.
Motors that use older bearings that require regular lubrication should be lubricated on a scheduled basis, in accordance with the manufacturer’s recommendations.
Motor bearings can be classified into three main types according to their shapes and functions.
- Sleeve bearings are the simplest type of bearing. They are made of a single piece of metal and are lubricated with grease. They are typically used in smaller motors and motors that do not need to carry heavy loads.
- Ball bearings are the most common type of bearing. They are made of two or more balls that are held in place by a cage. Ball bearings are lubricated with oil and can carry heavy loads. They are typically used in larger motors and motors that need to operate at high speeds.
- Roller bearings are similar to ball bearings, but the balls are replaced with rollers. Roller bearings can carry even heavier loads than ball bearings and are typically used in motors that need to operate at very high speeds.
In addition to the three main types of bearings, there are also thrust bearings. Thrust bearings are designed to handle axial forces, which are forces that act parallel to the shaft of the motor. Thrust bearings are typically used in motors that have fans or pumps attached to them.
The type of bearing that is used in a motor depends on the size, speed, and load of the motor. It is important to choose the right type of bearing for the application to ensure that the motor operates smoothly and efficiently.
Electrical Connections
Motor installation is a complex process that must be done in accordance with the manufacturer’s instructions, NEMA standards, and local codes.
The first step is to verify that the motor is compatible with the power source. The motor’s nameplate will indicate the voltage, frequency, and current requirements. The power source must match these requirements or the motor will not operate properly.
Once the compatibility has been verified, the motor can be connected to the power source. The stator winding connections must be made as shown on the nameplate connection diagram or in accordance with the wiring diagram attached to the inside of the conduit box cover.
It is also important to secure the motor to a solid foundation. The motor should not be able to move or vibrate during operation.
After the motor has been installed, it is important to perform a safety inspection. This inspection should include checking the motor’s connections, insulation, and bearings. Any problems that are found should be corrected before the motor is put into operation.
Grounding
Motor grounding is important for safety and to prevent bearing damage.
When a motor is not properly grounded, electrical currents can flow through the motor’s bearings. This can cause the bearings to heat up and fail prematurely.
To prevent this, motors should be grounded to a metal object that is in contact with the earth. This can be done by connecting the motor’s frame to a grounding rod or to the metal conduit that the motor is connected to.
In addition to preventing bearing damage, grounding motors also helps to protect people from electrical shock. If a motor becomes energized, the grounding conductor will provide a path for the current to flow to the earth, preventing it from reaching a person.
The grounding conductor should be a green or green with yellow stripe conductor. It should be sized according to the motor’s current rating.
Motor grounding is an important safety precaution that should not be overlooked. By properly grounding your motors, you can help to prevent bearing damage and protect people from electrical shock.
Here are some additional things to keep in mind when grounding motors:
- The grounding conductor should be connected to the motor’s frame at a point that is as close to the motor as possible.
- The grounding conductor should be continuous and free of splices.
- The grounding conductor should be protected from physical damage.
Voltage Levels and Balance
Motor voltage variations and unbalances can have a negative impact on the performance and lifespan of a motor.
Motors are designed to operate within a specific range of voltages. If the voltage deviates too much from the nameplate value, it can cause the motor to overheat, draw more current, and lose efficiency.
Unbalanced voltages can also cause problems. When the three-phase line voltages are not equal in magnitude, it can create unbalanced currents in the motor windings. This can lead to overheating, insulation damage, and reduced motor life.
The acceptable level of voltage unbalance depends on the type of motor. For most motors, an unbalance of 1% or less is considered acceptable. However, in some cases, a higher unbalance may be tolerated.
If the voltage unbalance exceeds the acceptable level, it is important to identify and correct the source of the problem. This may involve upgrading the power distribution system or rebalancing the loads on the motor.
By keeping motor voltages within the acceptable range and minimizing voltage unbalances, you can help to ensure the long-term performance and reliability of your motors.
Here are some additional tips for minimizing the impact of voltage variations and unbalances on motors:
- Use a voltage regulator to keep the voltage within the acceptable range.
- Balance the loads on the motor to minimize the amount of unbalanced current.
- Install surge suppressors to protect the motor from voltage spikes.
- Inspect the motor regularly for signs of overheating or insulation damage.
Percent voltage unbalance = (Maximum voltage deviation from the voltage average / Average voltage )× 100
Built-in Thermal Protection
Overload relays and thermal protectors are used to protect motors from overheating.
Overload relays are typically mounted on the motor starter enclosure and monitor the motor current. If the current exceeds a preset value, the overload relay will trip and disconnect the motor from the power supply.
Thermal protectors are devices that sense the temperature of the motor windings. If the temperature exceeds a preset value, the thermal protector will trip and disconnect the motor from the power supply.
Overload relays are effective in protecting motors from overheating due to excessive current. However, they do not monitor the actual temperature of the motor windings. This can be a problem in applications where the motor is subject to high ambient temperatures or inadequate ventilation.
In these applications, it is advisable to use thermal protectors in addition to overload relays. Thermal protectors can sense the actual temperature of the motor windings and will trip the motor if the temperature exceeds a safe level.
There are two main types of thermal protectors: automatic reset and manual reset. Automatic reset thermal protectors will automatically restore power to the motor once it has cooled down. Manual reset thermal protectors require the operator to manually reset them before power can be restored to the motor.
Resistance temperature detectors (RTDs) are a type of thermal protector that uses precision-calibrated resistors to measure the temperature of the motor windings. RTDs are typically used in conjunction with an instrument to detect high temperatures.
By using overload relays and thermal protectors, you can help to protect your motors from overheating and premature failure.
