When designing a new piece of equipment that uses motors or gearmotors, design engineers must calculate how much motor torque will be needed to drive their application load. If the gearmotor or motor is undersized and too small, the product will be underpowered and likely not meet all application requirements. If the gearmotor or motor delivers more power and torque than required, then it adds unnecessary cost, requires more space and can negatively affect the total weight of the equipment.

This tech note provides the design engineer with a procedure on how to check his or her calculations against real-world performance by load testing the application. A good way to determine how much the actual load is on a motor or gearmotor is to measure the amount of current it draws. Three-phase brushless DC (ECM) motors present a challenge to the engineer who wants to measure motor current. If the current is measured through the motor leads (i.e. the motor phases), the resulting current values will be useless and essentially make no sense.

There is a simple way to accurately measure the current through the motor: measure the current through the motor fuse on the brushless DC control.*  The current measurement provides the DC bus current before it goes into the 3 phases of the motor, and therefore can be used to calculate the load (torque) at the motor/gearmotor shaft. This is possible because just as in PMDC motors or gearmotors, the measured current is directly proportional to the load (required torque). The measured DC bus current should be very close, if not equivalent, to the nameplate rated current, if the motor or gearmotor is loaded to the nameplate rated torque. Once the current measurement is obtained, the motor torque is calculated by multiplying the torque constant (Kt) for the motor/gearmotor by the current value measured. Gearmotor output torque can be calculated once the motor torque has been determined.

Kt (oz-in./A) x I(A)=T (oz-in.)

Test Procedure:

FIGURE 1. Motor fuse location on a Bodine type ABL-3911 control

FIGURE 2. Location of motor fuse and quick connect tabs M+ and MF3.

FIGURE 3. Connect ammeter and external fuse holder to M+ and MF3.

1. Remove the motor fuse from the on-board fuse holder.
2. Connect floating wires to M+ and MF3.
3. Place the motor fuse into an external fuse holder.
4. Connect the fuse holder and the ammeter in series with M+ and MF3 as shown in figure 3.
5. Measure the DC current using an ammeter.

* This test will only work with a non-PWM control, such as Bodine type ABL-3911 and ABL-3921. It will not work with a PWM control, such as Bodine’s low voltage models ABL-3905 or ABL-3907.

Eman Elashye is an Application Support Specialist at Bodine Electric Company. She has a degree in Electrical Engineering and works in their customer support group in the Chicago area.

You can download the PDF version here: Bodine Application Notes

p.s.: This method also works with our non-PWM DC motor speed controls and permanent magnet DC (PMDC) gearmotors and motors.

Bodine type 34B-HG Brushless DC Gearmotor

A ”traction motor” is a motor or gearmotor used in a traction application. Golf carts, electric vehicles, locomotives, lift trucks, etc. Often “traction motors” also have mounting features, temperature sensors, wiring terminals that are useful in mounting the motors in a vehicle. They may also have a higher level of environmental protection against dust and moisture. 

2011 Bodine Standard Products Catalog S-17

The all-new Catalog “S-17″ is here! We completely redesigned our standard product catalog to make it even easier for you to find the right gearmotor or drive system for your application. Designed as a print companion to our web site, it features detailed specifications for over 1,200 AC induction, permanent magnet DC (PMDC) and brushless DC (ECM) gearmotors, motors and motion controls.

Bodine Catalog S-17 Download Page

Back EMF with sensors aligned

A sensorless brushless DC control consists of a power supply, a power stage, commutation logic, and startup logic. The key difference to an electronically commutated BLDC motor system is that the Hall sensor inputs are replaced by a system that measures generated voltage (BEMF = back EMF) and uses zero crossings to determine when to switch on (energize) the windings. 

The screen shot on the right shows BEMF with hall sensor aligned to commutate a conventional BLDC (ECM) motor or gearmotor.

How does the sensorless BLDC control work?

The BLDC motor is started “open loop” by sequencing the power switches to start rotation. Usually this involves a fixed time interval based on inertia to accelerate the motor. Once the motor speed is high enough to “read” BEMF signals the commutation loop is closed allowing normal brushless motor operation.

What are the limitations of a sensorless BLDC system?

The initial BEMF detection is based on motor speed. Hence, the motor has to achieve a minimum speed for the BEMF sensing to work. In addition, BEMF sensing requires filtering to remove PWM noise. The filtering of the signals introduces delays in the measurements. All these limitations result in a speed range limitation that is normally between 5:1 and 10:1. Another issue that occurs with a sensorless BLDC motor and control system is that the motor shaft will likely move prior to starting up.

What are the benefits of a sensorless BLDC system?

This simplified motor-control connection scheme might reduce the risk of mis-wiring the motor and control system.  In addition, one should see cost savings due to the elimination of hall sensors in the motor, and because less cables and connections are required. A sensorless BLDC motor will be a less complex assembly, the lack of an internal commutator might also allow for a slightly smaller motor size.

What is Back EMF?

Back EMF is the voltage produced across a winding of a motor due to the  winding turns being cut by a magnetic field while the motor is operating. This voltage is directly proportional to rotor velocity and is opposite in polarity to the applied voltage (sometimes also referred to as counter EMF)

Back EMF from two motor phases after filtering

Back EMF definition from the Bodine Electric Small Motors Handbook - Glossary of Terms (p. G-2)

Gearmotors with Built-In 24VDC Brushless Control:

To minimize wiring and connection challenges with electronically commutated BLDC (ECM) motors and gearmotors, Bodine Electric offers a stock selection of INTEGRAmotors and gearmotors. Our INTEGRAmotors offer a cost competitive, all-in-one, easy to wire brushless DC drive solution for specialty machine builders and OEMs that don’t want to deal with high-cost and very complex stepper or servo systems. For more info, click here: INTEGRAmotor, a smart choice…     

Bodine INTEGRAmotor - BLDC (ECM) Motors and Gearmotors with Built-in Controls and Feedback

As always, we hope you find this information interesting. If you have comments or questions, please leave your comment here, or send an e-mail to: edmund.glueck@bodine-electric.com  

Regards, Edmund  [Manager, Marketing and Product Development/Standard Products] 

 Copyright  Bodine Electric Company ©  11/2010.  All rights reserved.

Bodine Brushless DC (BLDC) Gearmotors, Motors and Controls

One of our authorized distributors called our Tech Support staff in Chicago recently because his customer was having problems with a Bodine 34B4BEBL brushless DC motor and our ABL-3911 control. Our products were designed into a new machine that is used to induction-harden steel shafts.

1) Because of the distance between the motor and the control, the customer had made his own wiring harness instead of using a pre-made cable kit, like our model 3983. Because of a termination error with their home-made wire harness, they connected the signal common to earth ground and destroyed one control. Not only did they blow up an IC on the control board but they also damaged a Hall effect sensor in the motor.

2) The problem they were having was that when the control was turned on, the motor would not rotate. The motor shaft just vibrated in place. This can be the case when the motor phases are energized in the wrong sequence. We asked the distributor to make sure that the Hall effect sensor wires weren’t connected wrong. We also suggested that one way they could rule out the possibility of the homemade cable having any shorts or wrong connections in it would be to use Bodine’s Model 3983 cable kit just for testing. If the motor and control operated properly with our Model 3983, then we would know that the homemade cable was the source of the problem. However, the customer insisted that they had already checked and double-checked their wiring and that it was correct.

Brushless DC Motor Connections

3) Fortunately, our distributor checked it as well, and found that two wires had indeed been crossed. After this had been corrected, a new problem showed up. Now the customer reported that when they turned the control on, the motor sped up by itself and then stopped by itself. It wouldn’t start again after that. At this point, the distributor asked our Tech Support staff member to join him at the customer’s plant.

4) We looked the system over and confirmed that it wouldn’t start. We checked the dip switches and confirmed that they were in the proper positions for the motor that was being used. We asked if either of the fuses was blown. The customer insisted that they’d checked the fuses and that they were fine. Again, the distributor checked as well and found a blown control fuse. We replaced the fuse and turned the control on. The motor sped up by itself and after a while stopped by itself just as the customer had described. The motor fuse was blown again. We now also realized that the acceleration potentiometer was turned fully clockwise (for longest acceleration time) which made it seem that the motor was speeding up by itself. In actuality, it was just taking a long time for the motor to accelerate to the set speed. We then turned our attention to the fuse that kept blowing.

5) We explained to the customer that Bodine’s ABL-3911 control, when configured for our 34B4BEBL BLDC motor, uses a 2 amp motor fuse and that, since the fuse is blowing, the motor must be drawing more than 2 amps for an extended period. Since current draw is directly proportional to the motor load for a brushless DC motor, the motor must be overloaded. We put a new fuse in and measured the current draw. The motor was drawing 4 amps. We also noted that the current increased significantly as we increased the motor speed, which led us to question the suitability of the customer’s load bearing for high speed operation. We checked the bearing and the chain between the motor and the load.

6) The chain was so tight that we could not budge it. When they loosened the chain, the current dropped down to 2 amps. The bearing they were using was not lubricated and seemed to be misaligned. When it was replaced with a lubricated bearing, the current dropped to less than 1 amp. We now had a happy customer who could demonstrate his new machine to his customer.

This is not the first application support call where the motor and control were blamed for a problem when, in fact, the problem was just a symptom of the true problem.

To identify and solve the root-cause of the problem, we did the following: (1) we checked and corrected the wire connections, (2) we confirmed that the control’s dip switches were set properly, (3) we checked and replaced blown fuses, (4) we measured the current draw of the motor under load and determined that it was overloaded, and (5) we identified ways to reduce the load.

Copyright  Bodine Electric Company ©  11/2010.  All rights reserved

Metric Motors and Gearmotors from Bodine Electric Company (USA)

Our selection of metric AC induction and permanent magnet DC products features special motor windings for many international markets and 50Hz applications. These gearmotors and motors also feature metric drive shafts and metric mounting threads.

Fixed speed AC motors are available with permanent split capacitor, split-phase, and three-phase windings. AC metric motors are rated 230 VAC, 50 Hz, single-phase, or 230/400 VAC, 50Hz, three-phase. Permanent magnet DC motors are available with a voltage rating of 180 VDC (F.F.=1.6, designed for continuous duty operation). Custom AC and DC windings can be provided to match almost any international rating.

We offer a complete line of both AC and DC metric right-angle and parallel shaft gearmotors. Torque output for AC gearmotors and motors ranges from 0.021-43 Nm. Fixed-speed models are available with speeds from 7-280 1/min (revolutions per minute). Output torque for our PMDC products ranges from 0.18-43 Nm with rated speed range from 5.8-345 1/min (rpm).

Bodine PMDC Motor Speed Controls Model 0865, 0866, 1865 (0-180VDC, at 230VAC)

Our 180 VDC metric PMDC motors and gearmotors are designed to operate with filtered and unfiltered PMDC motor speed controls and are rated for either F.F.=1.0 or 1.6. Bodine Electric Company also manufactures DC motor speed controls for these 180VDC gearmotors and motors. Our type “UPM” stock models, 0865 and 0866, are unfiltered SCR speed controls that operate from a 115/230, 50/60Hz input and can provide either 0-90VDC (at 115VAC input), or 0-180VDC (at 230VAC input). Bodine also offers an enclosed version of this DC motor control; see stock model 1865.

Pacesetter™ AC variable speed, inverter duty, three-phase gearmotors and motors are available in non-metric versions only, but can be operated with a 230/50Hz inverter (AC variable frequency drive) when the drive’s motor output frequency is set for 60Hz motors.

These gearmotors and motors are also available through Bodine Electric’s worldwide distributor network. The standard lead-time for our metric models is 4 weeks.

Explore:  Metric AC Motors and Gearmotors; Metric PMDC Motors and Gearmotors; DC Speed Control Models: 0865,  0866,  1865; Pacesetter AC Inverter Duty Gearmotors;  Custom Options and Solutions

Copyright  Bodine Electric Company ©  11/2010.  All rights reserved.

The WX is a parallel shaft gearhead that can deliver up to 210 lb-in (24 Nm) continuous torque. This new gearhead complements Bodine’s smaller type D and Z gearheads that produce up to 120 lb-in (14 Nm) of continuous duty torque, and the larger type E/F, HG, and CG gearheads that range from 250 to 1000 lb-in (up to 113 Nm) of continuous torque. 

New Bodine WX Gearmotors

The exterior of the new WX gearhead is identical to Bodine’s old type “W” gearmotor models, but the inside has been completely redesigned. These new WX gearmotors feature all-steel helical gear trains and synthetic lubricants, allowing the type 33A-WX (PMDC) and 34B-WX (BLDC) to produce up to 65% more torque than previous type “W” models. The new steel gearing is designed to AGMA 9 standards or higher, to assure the quiet operation that is expected from Bodine Electric products. The synthetic lubricant in this new gearhead improves efficiency, and allows these gearmotors to operate in a wide temperature range. 108 new stock models feature 12 available gear ratios, ranging from 4:1 to 312:1, and rated output speeds from 658 to 8 RPM.

As with most Bodine gearmotors, the new WX gearhead is offered with a range of motor options to provide customers with the flexibility and design solution that best fits their application needs. The WX  gearhead is stocked with a new AC fixed speed, 3-wire-reversible motor winding; two permanent magnet DC motor options, either rated 90/130 VDC or 12/24 VDC; and brushless DC WX models, type 34B-WX, are offered with a 24 VDC or 130 VDC winding option.

Bodine WX Accy Kit Model 0995 3-Point-Mtg Adaptor

These new WX models are “cURus” marked, and are designed and manufactured to be RoHS compliant. All new WX stock models can be configured to feature a 3-hole mounting pattern via a simple bolt-on adaptor plate (which allows the WX to be a drop-in replacement for similar gearmotors from other manufacturers).

Bodine 34R-WX AC Fixed-Speed Gearmotor

34R-WX [AC]: The WX gearhead is the first gearhead to be paired with Bodine’s new 3-wire reversible 34R (4 inch/100 mm diameter), single phase, 1/7 HP (107 Watts) motor winding. The three-wire configuration simplifies connection, and makes reversing the motor’s direction simply a matter of switching the position of two leads. This new winding can also operate at 50 Hz by utilizing a different value run capacitor. A new 230VAC, 50/60Hz, 1-phase, 3-wire reversible winding is also available for custom configurations.

Bodine 34B-WX Brushless DC (ECM) Gearmotor

34B-WX [BLDC]: The WX gearhead is available with Bodine’s type 34B, TENV, 1/5HP (149 Watts) brushless DC motors. These electronically commutated (BLDC) motors require less maintenance and last longer than traditional brush-type PMDC motors. The brushless construction results in a cooler running, quieter motor that can accelerate and decelerate quickly. They can be used in place of brush-type motors in applications where high starting torque and linear speed-torque characteristics are critical. The new 34B-WX gearmotors are offered with 130VDC and 24VDC windings and are available with or without accessory shafts for external encoder or brake installation.

Bodine 33A-WX PMDC Gearmotor

33A-WX [PMDC]: The WX gearhead is also available with Bodine’s 33A-frame permanent magnet DC, 1/4-1/11 HP motors. These motors provide high starting torque and linear speed torque characteristics. The 33A-frame motors feature permanently lubricated ball bearing construction for maintenance-free operation, as well heavy gauge steel housing and copper graphite brushes. The windings are resin-impregnated. Bodine PMDC motors feature an unique skewed armature design to minimize cogging and operate quietly over the full speed range.

Bodine Quick Delivery Program for Stock Gearmotors

The New Bodine type WX Gearmotors. For additional information, click here…

Copyright  Bodine Electric Company ©  05/2010.  All rights reserved.

As a manufacturer that exclusively focuses on fractional horsepower (less than 1HP/746 Watts) products, Bodine Electric also has the engineering expertise to design and manufacture a great variety of custom winding types and ratings. 

AC Induction motor windings:  are available in single-phase, two-phase and poly-phase (three-phase) designs including the following types; split-phase (with centrifugal start switch), capacitor start, permanent split capacitor, 2 capacitor start, 2 capacitor start/one capacitor run, and reluctance synchronous. These windings can be produced in 2-, 4-, 6- & 8-pole configurations and can be rated as continuous duty, intermittent duty, inverter duty, dual voltage, dual frequency and multi-speed. Our windings are available in voltages ranging from 12 to 575 VAC. Bodine Electric also provides solutions for OEM applications that require thermal overload protectors with manual or automatic resets, or simple temperature limiting switches. 

AC Motor Stators - In-Process and Finished (Bodine Electric Company)

Features/Benefits of various AC Motor and Gearmotor Designs:   This table was created to help you better understand the capabilities, advantages, and disadvantages of the numerous AC motor and gearmotor windings that are offered by Bodine Electric Company. Click on this link to learn more about our range of available AC motor windings:  

http://www.bodine-electric.com/Products/Asp/ACMotorAdvantages.asp 

 

Permanent magnet DC motors: are available with rated voltages from 12 to 240 VDC. They can be designed in 2 & 4 pole versions and in lap or wave (4 brush vs. 2 brush) configurations. Multiple magnet grades are available for enhanced performance or added demagnetization protection. End-of-life signaling brushes, and a new proprietary brush wear sensor system are also available from Bodine Electric Company. 

DC Motor Armature – Finished and In-Process (Bodine Electric Company)

 

Brushless DC (ECM) motor windings:  Similar options and winding configurations are available for Bodine Electric’s growing line of Brushless DC (electronically commutated) motors and gearmotors. Our standard brushless DC windings are 3-phase, 4-pole designs (standard voltages are 24 VDC and 130 VDC).  Bodine Electric Company introduced the first BLDC motors, gearmotors and motor speed controls in the 1980s. Since then, we have expanded our product offering to a wide selection of custom designs with voltages ranging from 12 VDC to 260 VDC, and horsepower ratings up to 1HP/746W (our new type 48B motors/gearmotors). In addition, we offer our unique 24VDC INTEGRAmotor™ product line of brushless DC motors with built-in motor speed control and motor feedback device; and our innovative direct drive e-TORQ™ motor technology. Our standard 7-inch diameter e-TORQ motor is a 8-pole machine, the larger 14-inch diameter motor features a 16-pole winding.

Bodine Type 34B Brushless DC Motor (cutaway view)

 

Bodine Electric Company designs, develops, and manufactures all offered motor windings – AC and BLDC stators, and DC motor armatures.

 

DC Motor Armature - Winding Cell (Bodine Peosta Plant)

 

 Learn more about our full range of products at: www.bodine-electric.com  

  

AC & BLDC Motor Stator In Process - Winding Cell (Bodine Peosta Plant)

Copyright  Bodine Electric Company ©  03/2010.  All rights reserved.

Permanent Split Capacitor (PSC) Motors, Bodine Electric Company

Capacitors for permanent-split-capacitor (PSC) and capacitor-start (CS) AC induction motors are sized by motor manufacturers to produce adequate starting torque for most fractional-horsepower (FHP) applications.  To increase starting torque, users sometimes replace factory-installed capacitors with larger ones.  But tampering with recommended capacitances could adversely affect some important motor parameters such as starting current and running efficiency.  If these parameters get too far out of line with motor-design specifications, windings overheat and ultimately burn out.  Here’s how PSC and CS motors operate, and how changes in capacitance affect motor performance.

Capacitor Start Motors

The CS motor is essentially a split-phase motor with a capacitor for starting (see our catalog S-16, page 43, or the Bodine Handbook for additional info).  The motor has two windings:  a main or run winding, and an auxiliary or start winding.  The start winding is used only for starting the motor.  The run winding is energized for starting and running.  Because of the capacitor is in the start winding, currents in the two windings are out-of-phase.  This out-of-phase relationship sets up a rotating magnetic field that starts the rotor turning.  When the motor accelerates to approximately 70% of its normal operating speed, the start winding and capacitor circuit are disconnected by a speed-sensitive centrifugal switch, a current-sensing relay, or other means.

Motor Capacitors for Fractional Horsepower Motors and Gearmotors (left to right: Electrolytic, Film-, Oil-Type)

The capacitor value has no effect on the running performance of the CS motor.  However, starting torque and current both increase with capacitance.  Motor manufacturers select capacitor values to meet the starting torque requirements of typical applications without exceeding the current capabilities of the motor and its circuits.  Typical CS motors have capacitors that produce maximum starting torques of about four times the full-load running torque.  If more starting torque is required and if the motor circuit can safely provide additional current, some users replace the manufacturer’s standard-rated capacitor with one of greater capacitance.  However, this is usually done at the expense of other parameters.  And if the capacitance increase is excessive, starting torque may actually be reduced.

For a typical 1/15 hp CS motor, a capacitor with double the capacitance of the rated capacitor will only increase starting torque 50%, and starting current is almost doubled.  For some circuits, this increase in starting current may be unacceptable.  Other equipment such as lights on the same branch circuit with large motors may be affected by possible line-voltage drop.  Also, the life and reliability of the winding and centrifugal switch or starting relay in the motor is reduced by increased current.

Because the capacitor is connected only while starting, its duty cycle is highly intermittent.  Thus, the capacitor can be an inexpensive and relatively small AC electrolytic or metalized film type.  A normal, non-polarized, AC electrolytic capacitor consists of two aluminum plates separated by a porous paper which is saturated with an electrolyte.  Because these capacitors are not designed for continuous duty, the maximum on-time should not exceed 3 seconds and the maximum number of 3-second starts should generally not exceed 20 per hour (metalized film type capacitors are available for continuous duty operation).  However, most applications start in less than 3 seconds so that the number of starts can be increased in proportion to the decrease in starting time.  For example, a typical 0.5-second start permits the motor to be started 120 times per hour.

If the number of starts is too frequent or too long, windings and capacitors will overheat and motor reliability will decrease.  In such cases, a Permanent-Split-Capacitor motor should be used.  Also, PSC motors are more suitable for applications where frequent reversing is required, since the CS motor is reversible only from its rest position because of the starting switch.

Permanent-Split-Capacitor Motors

Motor Run Capacitors (plastic box type); Metallized Polypropylene Film.

A Permanent-Split-Capacitor motor is similar to a CS motor and also contains two windings:  a main winding and a capacitor winding.  In a PSC motor, however, the capacitor winding is permanently connected in series with an AC oil-type or metallized film capacitor.  Unlike the CS motor, the auxiliary winding and capacitor are energized during both starting and running.  Thus, continuous-duty ac oil-type or metalized film capacitors are installed in PSC motors.  The dielectric in the capacitor is an oil-impregnated paper or plastic film as opposed to the aluminum oxide in ac electrolytic capacitors.  The oil-type capacitor is inherently larger and more costly than the metallized film or electrolytic type.

AC (Fixed Speed) Induction Motors and Gearmotors from Bodine

The PSC motor operates similarly to a two-phase motor and is, therefore, inherently more quiet and efficient than a CS motor.  However, the phase angle in a PSC motor changes with load so that the motor usually is less efficient during starting than during running.  In usual motor design, a compromise is made between the two operating points.  Changing the capacitor value as specified by the manufacturer will affect both running and starting characteristics so that any improvements in starting usually decrease running performance.  For example, a 200% increase in capacitance in a typical 1/15-hp motor approximately doubles the starting torque.  However, the running efficiency of the motor drops from approximately 50% to 18%, and serious overheating of the motor results. Many motors are designed to operate close to the thermal limit of their insulation class rating. An increase in capacitance can increase the winding temperature rise above the allowed limit.

Some PSC motors use a second capacitor for starting purposes only.  This second capacitor may be an electrolytic or metallized film type.  This version is called a two-capacitor motor or a two-capacitor-start, one-capacitor-run motor.  Two capacitors preserve the efficiency and quietness of the PSC motor when running while improving the starting characteristics.  By using one capacitor for running and another in parallel for starting, starting torque can be increased without impairing running performance.  An analysis of the PSC speed-torque curve reveals that where acceleration is important, it would be wise not to use too large a capacitance for starting purposes.  In fact, even though the starting torque may be the same for two values of capacitance, the average accelerating torque may be less for the larger capacitance.

Supporting Images and Charts:

1) How to read a Speed-Torque Curve (Bodine Handbook, page 7-25)

2)  Bodine Type 42R5”CI” AC Motor Example with various Capacitors

1 – Rated Speed and torque (approx. 98 oz-in at 1700 RPM, 4-pole) 2 – Breakdown Torque   3 – Starting Torque

Comments to above graph:

 A) Changing the factory specified capacitor to a different than rated value will void the product warranty, may affect motor performance, and/or can lead to product failure.

B) The above graph is an example only! The gains shown may or may not apply to any  Bodine AC, PSC stock windings. Motor heating, insulation class limits, and current draw must be reviewed on a case-by-case basis!

• the synchronous speed of a 4-pole AC motor at 60Hz is 1800 RPM
• this particular winding example has slightly more starting torque than running torque
• effects from capacitor change vary from frame to frame, and winding to winding
• increased capacitance (>100%) will increase current draw and power consumption
• the motor’s duty cycle will have to be reduced if capacitance is chosen too high
• increased current draw from a larger capacitor might cause fuses or breakers to go off/trip
• capacitor changes will affect the motor’s power factor/phase angle, which in turn, will affect current draw, power and heat…

Click here, to download a PDF version of this article.

By Edmund Glueck.  Copyright  Bodine Electric Company ©  01/2010.  All rights reserved.