Best starting torque in the industry

07/16/2007

Franklin Electric motors have the highest starting torque in the industry. Why does this matter? A motor needs enough force to overcome inertia and friction and start spinning. Without it, nothing moves: not your motor, not your water.

So how does it work? When a water system’s pressure switch closes, power flows to the motor. This energizes the stator and creates a rotating magnetic field that interacts with the rotor.. This causes the rotor to spin, thus turning the shaft and driving the pump.

All of this happens in the blink of an eye and while trying to overcome impeding forces. Friction is the main culprit, and it comes from various sources. These may include:

    1. Debris or mineral deposits lodged between the pump body and impellers
    1. The motor’s internal friction from radial and thrust bearings.
    1. The pump’s internal friction from bearings, wear rings and other points of contact between the impellers and pump housing.
    1. Friction due to misalignment or damage.


Because starting torque plays such a significant role in a motor’s operation, you should be familiar with the design characteristics of the motor you are considering. In North America, you might find the following single-phase design types:

    • 2-wire PSC (Permanent Split Capacitor)
    • 2-wire Split-phase
    • 3-wire CSIR (Capacitor Start Induction Run)
    • 3-wire CSCR (Capacitor Start Capacitor Run)


Starting Torque Chart
Typical Starting Torque of a 1/2Hp Motor

You should also keep in mind that the starting torque of any motor is a function of the voltage available at the motor terminals. In the event of a low voltage condition at start-up which may be due to a supply issue or drop cable size, a 5% reduction in voltage results in a starting torque reduction of nearly 10%. In this case, there is a higher risk that the lower torque PSC motor will not be able to start the pump.

In addition to the higher starting torque of Franklin 2-wire motors, they boast a feature that no other 2-wire motor in the world can claim: reverse impact torque. When starting torque alone is not enough to overcome a bound pump, Franklin’s reverse impact torque feature goes into action. It applies a repetitive forward and backward force to the shaft that results in a “machine-gun” or ratcheting impact. This will break free many bound pumps and allow them to run freely.

The next time you are selecting a motor, consider the importance of starting torque to the quality of your installation. You’ll see that Franklin motors “shake-out” above the rest.