TMEIC TMdrive-MVe2 Reactive Power Control

Exceptional by Design™

Built-in Reliability and Performance

What makes the TMdrive-MVe2 Exceptional by Design™?

• Very High Reliability - 15 year MTBF

• Simple design

• Clean power to the utility system & motor

• Built-in Reactive Power Control

• Minimal spare parts

• Long-life film capacitors

• 24 hour x 365 day live support in North America

• Remote Connectivity troubleshooting built-in

Let's focus on the TMdrive-MVe2's Exceptional by Design™ feature:  Built-in Reactive Power Control

All Variable Frequency Drives (VFDs) provide motor speed control (with potential energy savings and improved process control),

and some degree of motor protection.  Voltage-source VFDs (typically with diode rectifiers and capacitor DC link) isolate the

poor power factor of their connected motors from the utility.  For example, a motor with a power factor of .82 lagging would

have its power needs met by the output of the VFD, while the input reflects a much improved power factor of (typical) 0.95

lagging.

TMEIC’s TMdrive-MVe2 VFD input converter is configured with a unique “Active Front End” that uses active switches in place of

diode rectifiers.  This allows the converter of the VFD to hold unity power factor at its input terminals.  But the TMdrive-MVe2

and control goes beyond that and can actually correct the system Power Factor demands of other nearby utility loads without

adding capacitors.

Utility Plant Power

Typical Industrial loads such as shown in the one-line below consist of motors for plant processes, special equipment unique

to the facility, and other loads such as plant lighting and HVAC.  In AC systems, the current that flows is divided into two

components, real power measured in kiloWatts (kW) and reactive power measured in kilovars (kVARs).  Both types of power

draw current (amperes) from power delivery equipment such as transformers, cable, and switchgear.  Current flow results in

voltage drop, heating and wasted energy.

kilowatts and kVARs

What is a kilowatt?  kW is the accepted measure of the real energy consumed by any process.  It is the product of volts and the

part of the total amps flowing that does real work, divided by 1000.  This current is called “real” current, and flows in phase

with the voltage.  This includes the “work” that produces heat in the cables and power delivery gear.

Describing “What is a kVAR?” is a little more difficult.  A kVAR is the accepted measure of reactive power, equal to the product

of the volts and the part of the current that is “reactive” divided by 1000.  Reactive current is the current that flows out of

phase with the supply voltage.  Reactive current supplying motors lags in time behind the voltage and the real current, as in A

below.  Reactive current that supplies capacitors leads in time ahead of the voltage and the real current, as in B below.  Lagging

reactive current magnetizes motors and transformers.

The real power (kW) and the reactive power (kVAR) are related like the legs of a right triangle as in the figure at the above

right. Each of the sides is shown as an arrow, called vectors. Since they are at right angles, they cannot simply be added together.

The longer vector (kVA) represents the total current (amperes) and the load on the system. The ratio [kW / kVA] of real power

(kW) to apparent Power (kVA) is called the power factor (pf).  The angle shown as A is the power factor angle.  If all kVAR were

eliminated, the apparent power (kVA) and real power (kW) would be equal and the power factor would be unit or 1.00.