Typical Problems, Superior Solutions
Pulse Width Modulated (PWM) power supplies and Variable Frequency Drives (VFDs) are typically used to improve energy efficiency. However, a major drawback to using PWM power sources and VFDs is that the output is a square wave form, which can cause major motor damage. Critical applications such as HVAC systems and oil field duty require a more sinusoidal output waveform, eliminating these economical and efficient solutions.
TCI’s KMG MotorGuard sinewave filter converts the PWM wave form to a near sinusoidal wave form by eliminating the carrier frequency, allowing sensitive applications to take advantage of the efficiencies and savings that PWM output power supplies and VFDs can offer.
For Lighter Variable Torque Applications
For lighter variable torque applications, we recommend the MotorShield Sine Wave Filter.
TCI now offers the MotorShield sine wave filter which provides the same sine wave filter performance as the MotorGuard, but in a smaller package. The MotorShield is the perfect solution for variable torque fan and pump applications.
Reflective Wave Phenomenon
Voltage wave reflection is a function of the voltage rise time (dV/dt) and the length of the motor cables.
The impedance on either end of the cable run does not match, causing voltage pulses to be reflected back in the direction from which it arrived. As these reflected waves encounter other waves, their values add, causing higher peak voltage.
As wire length or carrier frequency increases, the overshoot peak voltage also increases. Peak Voltages on a 460 V system can reach 1200 to 1600 V, causing rapid breakdown of motor insulation, leading to motor failure. On 575 V systems, the peak voltages can easily reach 2100 V. If this is left uncontrolled, insulation failure may occur.
Voltage without MotorGuard
Voltage with MotorGuard
- • Universal acceptance – can be used with virtually all AC induction motors, lead lengths and lead types and used with a wide range of carrier frequencies from 2 kHz to 16 kHz and beyond
• Reach long lead lengths up to 15,000 ft. for specific applications
• Increases the life of your motor by eliminating voltage wave reflection and torque ripple
• Provides motor and cable protection by reducing motor noise, vibration and heat
• Ideal for constant torque applications
MotorGuard Typical Applications
- Extreme long motor lead lengths. Applications can reach 15,000 feet
- Low voltage PWM power supply to medium voltage motor
- Multiple motor applications such as conveyors, blowers, pumps, and fans
- Test floor and test stand applications
- Shore to ship power for non-60 Hz systems
- HVAC systems to reduce audible noise
- Carrier frequencies from 2 kHz to 12 kHz
- Short Term Overload Rating: Tolerance 200% rated I for a maximum of 3 minutes
- System Voltage: 480 VAC, 600 VAC
- Insulation System: Class H (180° C) or Class R (220° C)
- Temperature Rise: 115° C or 155° C
- Ambient Temperature:
- Open Panel 50° C (122° F)
- Enclosed Panel 40° C (104°F)
- Distance: up to 15,000 feet
- Voltage Distortion: < 5% (typical)
- Agency Approvals: Industrial – cUL, UL
- Industrial Version: UL Open, UL Type 1
- (Legacy) General Purpose: NEMA 1 and 3R
Properly sized and applied, the addition of a MotorGuard Output Filter is guaranteed to bring the application into compliance with NEMA Standards Publication No. MG-1. If the system fails to meet MG-1 standards with the addition of a MotorGuard filter, TCI will take back the output filter and pay shipping both ways. This offer is valid for 60 days from installation date.