The worst thing that could happen in a commercial building is for the electric motor driving the HVAC system to fail during the coldest day of winter, and you’re left with the task of purchasing a new replacement. There is no shortage of suppliers or brands, and choosing the lowest cost amongst the various models seems to be a rational and simple decision.
But purchasing an electric motor is a long-term investment and there are various factors that affect the cost of ownership. Failing to consider these can mean greater costs that manifest after the unit has been commissioned.
Greater efficiency in electrical equipment has created a new consideration for cost of ownership. For example, LED lamps are quickly replacing fluorescent models despite the higher purchase cost. This is due to the higher efficiency of the LED lamps. The same consideration applies to electric motors as they are used to drive heavier loads and therefore consume more electric power. You do not want to make the mistake of getting a lower cost but less efficient electric motor and paying more in the long-term.
Besides being a bad investment, inefficiency often manifests itself as wasted electric energy in excessive heat. Efficiency of an electric motor can be attributed to various factors including its design, construction, material and operating condition.
As the power consumed by an electric motor is much greater compared to other applications such as lighting or appliances, even the slightest percentage difference in efficiency could mean significant financial saving over the lifecycle of the motor.
It is inevitable that electric motors do degrade and break down after prolonged usage. Bearings do wear out and winding insulation may fail after a period of time. The challenge in purchasing an electric motor is not getting one that is maintenance free, but one that requires lesser cost in keeping it operational.
For example, 3-phase motors generally require less maintenance compared to single phase or DC motors. Single phase motors may require frequent replacement of the start switches and capacitors while DC motors often need servicing of the brushes and commutators. Having frequent operational maintenance can indirectly increase the cost of ownership of an electric motor. While it is not always possible, converting a system to use a three phase motor over a single phase or DC motor can be more cost effective, even if additional controls are required.
Having said that, it is still important to have a proper preventive or predictive maintenance schedule to ensure that any anomalies in the electric motor are detected and corrected. Simple procedures for greasing the bearings can have a positive effect of increasing its lifecycle.
As with any electrical types of equipment, operating within the specified environment is crucial to prolong the lifespan and reduce breakdowns. The same applies to electric motors. Overheating and dirt accumulation have been some of the common factors of electric motor failures. These happen when operating guidelines provided by the manufacturer are not adhered to.
Some of these problems can be averted by ensuring the electric motor is operating in an optimal environment. An installation in a room with regulated temperature and proper ventilation will ensure the electric motor operates below its typical +40°C limit. The absence of dust by proper use of filters also ensure the electric motor enjoys minimal breakdowns.
While constructing the facilities to regulate temperature may seem expensive, the benefits of having optimal performance and less downtime could make it a smart financial decision.
4. Mechanical Stress
Electric motors are highly mechanical and it is only a matter of time before some of their moving parts degrade and require replacement. However, there are options that may prolong the lifespan of the electric motor and should be considered when making a purchasing decision.
A soft starter is a great complementary control that allows the electric motor to experience less torque during startup. The soft starter applies a lower voltage at startup before gradually increasing it to its nameplate value. This reduces the electrical and mechanical shocks on the system. Besides that, a soft starter also protects the motor from current overload and subsequent damages.
Another often overlooked source of mechanical stress on an electric motor is the installation process. An improper installation such as mounting the electric motor on an uneven surface can lead to internal mechanical issues. Poor alignment and overly tightened belts can also cause premature failures. It’s prudent that you’re getting the electric motor installed by a professional team and verified to avoid any damages from vibrational shock and excessive stresses.
5. Condition Monitoring
Despite the fact that an electric motor does suffer wear and tear, there are better ways to mitigate the problems than calling in the repair team after the motor has broken down. Sensor monitoring technologies can be equipped to alert the maintenance team of any anomalies and ensure that early planned remedial measure is taken.
For example, temperature sensors can be installed to capture the bearing and winding temperatures to prevent overheating issues. Amperage readings are also useful in providing early warnings of overloading symptoms. Coupled with software, these readings form useful historical data that enables the maintenance team to identify major problems long before they surface.
At the end of the day, the decision of purchasing an electric motor goes far beyond the initial product cost. There are other factors that greatly affect the reliability and efficiency of the motor that you should consider. In many ways, these factors not only affect the total cost of ownership of an electric motor, they make up the majority of the cost.