
Rotary
Converter Application
Notes
The Rotary Converter is designed to supply full running current to a threephase motor normally providing it with
full running torque. However, most motors will draw five times
their running current during startup. When used at its maximum HP
rating the Rotary Converter cannot deliver the full (5 times)
starting current to the motor and therefore cannot provide full
starting torque. For heavy startup loads a larger converter
should be used.
NOTE: You can always use a larger Rotary Converter than the HP
of the motor. There is no minimum load requirement for the Rotary
Converters. Some customers will install a Rotary Converter larger
than they need to accommodate any future additions to their
equipment. Below are the minimum size recommendations for various
applications.
. 
Sizing
For Load Types 
1. 
Motor Loads


A... 
TYPE
1 Motor Load: 

May be used up to the HP rating of the
converter.* For instant reversing (as for rigid tapping), size
according to TYPE 3 LOADS *Many restrictions apply. Most
applications require sizing the converter a
minimum of 50% larger (see all load types). Contact PhaseAMatic,
Inc. to verify load type. . 
B. 
TYPE
2 Motor Load: 

These include domestic & European
lathes without a clutch, some pumps, wheel balancers,
paper cutters, flywheel driven equipment, air
conditioners, blowers, woodworking band saws, dough
mixers, meat grinders, motors rated below 1000 RPM, etc.
Use a converter with HP rating of at least 50% larger
than HP of the motor.
. 
C. 
TYPE
3 Motor Load: 

These include Design "E" motors,
Taiwanese, Chinese, Brazilian, Mexican motors, pumps
starting under load, etc. Use a converter with twice
the HP rating of the motor.
. 
D. 
TYPE 4 Motor Load: 

These include laundry extractors, hoists,
elevators, etc. For these startup loads use a converter
with three times the HP rating of the motor.
. 
E. 
TYPE
5 Motor Load: 

Often hydraulic pumps, which come under a
momentary load during use will be loaded well beyond their
rated HP for the brief period of maximum PSI. Examples
includes bailers, compactors, paper cutters, shears,
pumps, etc. The HP of the converter must be at least as
high as the actual HP developed by the motor. To calculate
the HP developed, you must first find the actual amperage
drawn during maximum PSI. This is different from the rated
amps of the motor. Next you would divide the maximum
amperage by 2.8 to find the actual HP being developed by
the motor. That figure is the minimum size of converter to
be used. Example: A 10 HP compactor with a motor rated at
28 amps but draws a peak of 40 amps momentarily at maximum
compression. Divide 40 by 2.8 = 14.3 HP being developed,
use model R15 Rotary Converter. 

2. 
Resistive Loads


Resistive loads must use the Rotary type
converter, the Static type should never be used because it
would be damaged. There are two methods to determine the
HP of the converter to be used. One method is to take the
amperage rating of the equipment and divide by 2.8 to find
the equivalent HP. The other method is to take the KW
rating and multiply times 1.34 or divide by .75 to find
the equivalent HP of the equipment. 

3. 
Computer,
Rectifier & Transformer Loads


Transformers
and electric equipment (welders, lasers, EDM machines, CNC
equipment, computers, plating rectifiers, power supplies,
etc.) can operate on the Rotary Converter. Use the same
formula as for resistive loads to determine the proper
size converter to use.
If a 4wire wye input is required (all lines equal voltage
to ground), a three phase deltatowye isolation
transformer must be installed between the converter and
the equipment to change the delta power to wye power. 

4. 
Multiple
Motor Applications


Due
to the high inrush current required to start a motor (5
to 10 times the normal running current), most applications
require sizing the HP of the Rotary Converter 50% larger, or
more than the horsepower of the largest motor, or any
combination of motors started at exactly the same time.
The first motor started, if not running heavily loaded,
generates additional 3phase power back into the circuit.
You can then run additional motors, provided they are not
running heavily loaded and not all started at the same
time. A maximum of up to 3 times the HP rating of the
Rotary Converter can run at the same time, if not heavily
loaded, and not started simultaneously. For example, a 30
HP Rotary Converter potentially could run motors totaling
up to 90 HP. Contact factory for verification of sizing. 


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