How Voltage Drop Affects the Operation of Induction Machines

By Cole Ferguson

Induction machines do not like voltage drop. When talking about induction machines, what most people think about is the 3 phase AC induction motor. For the most part, the power output of an induction machine is directly proportional to voltage and current. If the voltage of a motor drops, the motor must draw more current to compensate. As long as the current being drawn by the motor is within the nameplate limits, this isn't necessarily something to worry about for short periods of time. However, over longer periods of time or with a significant voltage drop, there will be a negative impact on the performance of your induction machine.

Induction Machines Overheating

If a motor is drawing more current than it is rated for on the nameplate, the wires that make up the windings will start to overheat. Overheating for any extended period of time will lead to a loss of lifespan of the motor. If the amount of current it is drawing is too far outside the nameplate rating, the motor will burn out all together.

Battery Life Reduction caused by Induction Machines

If your motor is supplied power by a battery or battery bank, the drop in voltage and increase in current will drain the batteries faster. This is a critical factor when looking at motors supplied by predominantly solar or wind power, which store energy in batteries when there is a surplus of sun or wind and have loads that draw energy from batteries when there is insufficient sun or wind.

Loss of Speed and Torque in Induction Machines

This train is never going to move without the appropriate voltage| This train is never going to move without the appropriate voltage

Another thing that happens as voltage drops and current increases is a loss of speed and torque at the motor. This loss of speed and torque can negatively impact whatever process the motor is supplying.

If the speed and torque of the motor decreases enough, the motor will go back to its "starting" state. When starting, a motor requires large amounts of torque in order to start moving whatever load is attached to the motor. In order to get this starting torque, you require a large amount of current. So the current value spikes, which causes the voltage to drop even more! All of this results in a motor that doesn't move and could quickly burn out.

Be Sure to Have Proper Protection!

In order to protect your motors from burning out due to voltage drop, it is important that you size your motor protection relays appropriately so that they will trip when voltage drops and current spikes.

As always, thanks for reading!