Soft Starters vs. Variable Frequency Drive (VFD)
When an electric motor first starts, it takes large amounts of energy to overcome the weight of the motor and any residual magnetism, as well as the weight of any equipment connected to it, such as fan blades, pump impellers, or grinding blades. The sudden inrush of current and torque required to get the motor spinning can actually damage the motor itself and shorten its overall service life.
Soft starters and variable frequency drives are two devices that help protect the motor from damage. They’re used in commercial, industrial, and even some residential applications to help manage the loads that large electric motors can place on electrical systems and protect other devices from the power surges motors can cause.
Soft Starters
Soft starters use electronics like thyristors or silicon-controlled rectifiers to reduce the amount of voltage to an electric motor during the startup phase. This lowers the current and torque that the motor will experience as a result, allowing it to spin up large loads with less chance of damage to the windings.
They’re ideal for heavy loads that run at a constant speed, such as:
- Ventilation fans
- Pumps
- Grinders
- Compressors
- Conveyors
- And more
For more controlled stops, some soft starters can also be used to slow the motor down when shutting off the equipment.
VFD Motor Starters
Variable frequency drives use more complicated electronics to vary the voltage and frequency that an electric motor is supplied as it starts. It does this by:
- Converting the AC voltage to DC voltage with rectifiers
- Filtering the DC voltage to provide a steady, clean power source with minimal artifacts
- Inverting the DC voltage to create AC at the desired voltage and frequency
This allows for granular control over the speed of the motor during startup and the entire time the motor is running.
VFDs are ideal for commercial and industrial equipment that needs to adjust to changing loads or run at different speeds, such as variable-speed HVAC blowers that can save energy and adjust airflow as needed for comfort, variable-speed tools like saws or drills for extra control, or variable-speed pumps that can adjust to different flow requirements.
Choose Starter Products From PSI Power & Controls
When you need high-quality, custom-built electric motor starters for your industrial or commercial application, contact PSI Power & Controls. For over 60 years, we have supplied businesses throughout the U.S. with UL-certified custom control panels, OEM control panels, and emergency power solutions.
We feature both soft-start and VFD systems in custom enclosed panels. All our products feature the highest-quality components, with competitive pricing, full engineering support, on-time delivery, and a full 12-month materials and workmanship warranty.
Call PSI today at (704) 594-4107 or contact us online for long-lasting, reliable electric motor starters tailored to your facility, budget, and equipment.