What type of electric motor should I specify? A common question asked by customers when they are looking to order a hydraulic power unit . Electric motors typically come in two different classes; AC and DC motors, which are both able to power a range of applications and are the main driving force of a hydraulic power unit. As well as the two main types of motor, there are a number of subdivisions of these ranges with the DC motors in particular having a wide range of versions including stepper motors, servo motors, brush motors and synchronous variants. For most hydraulic applications , induction type variants are commonly used comprising of single phase to 3 phase motors. So, which variety of motor do I need for my application? To answer this question, we need to look at the type of application you are using and its function. So, for example, if you need a motor for a commercial vehicle application such as a tipper, tailift or trailer the DC motor will suit your needs, whereas AC motors are more commonly found in car lifts, security barriers and dock levellers. It is therefore always necessary to specify your end use application first when enquiring about which motor you require. Mounting the motor One important fact to remember when positioning your electric motor on a power unit is its location away from other components. It is always recommended to leave sufficient space to allow the motor to breathe effectively especially if your system will be running high temperatures. It is essential to give the motor enough clearance from the cooling fan to avoid unit vibrations and possible damage to the bearings and shafts. Appropriate fixing methods should be used including bolts and shims with the correct torque levels applied. As well as the motor mountings, the general level of the ground the power unit stands on should be even as any kind of tilt could affect the motor should it suffer any short circuit forces while operational. Operational temperature considerations Electric motors are typically configured to run to temperatures from -20C up to +40C and the information on the motors running plate should be strictly adhered to. As well as the recommended running temperature range, motors should not be subjected to altitudes above approx. 1,000m above sea level. Failing to keep to these requirements could cause a potential safety risk or injury. Important general points to observe when running an electric motor • Avoid touching and getting in close contact with the motor while it is running as they can get very hot and have the potential to cause injury. Even when they have been shut down, the heat in the immediate vicinity can continue to cause a problem. • Take care to avoid rotating parts on the motor whilst it is in operation • While the unit is energised it is imperative that the terminal boxes are not touched or opened as this could lead to a safety hazard Motor maintenance In order to maintain the reliability of the motor, manufacturer service schedules should be strictly adhered to and individual motor components such as seals and bearings should be regularly inspected for any wear or damage and replaced as necessary.