Northern Lights APM 2000 Instruction

FOR

PARALLELING MODULE

APM 2000

INTRODUCTION

The APM 2000 Paralleling Module (part number
9 1473 00 100) is designed for use with the Basler APR63­5, APR125-5, and XR2002 voltage regulators. The APM
2000 is designed for the standard paralleling schemes,
known as reactive droop compensation and reactive
differential compensation. An externally connected
unit/parallel mode switch (S1) prevents unwanted voltage
droop caused by the regulator's working on the generator
output and not on the bus load.

The APM 2000 operates in conjunction with an external
parallel current transformer. The APM 2000 then provides
the droop signal necessary to two or more generators to
share reactive loads and reduce circulating currents
between them.

The voltage regulator and Paralleling Module must be
connected into the generating system as shown in the
Interconnection diagrams.

ELECTRICAL SPECIFICATIONS

CT Input

Nominal Rating: 1 Aac or 5 Aac
Range
1 A Input: 0.7 to 1.0 Aac
5 A Input: 3.5 to 5.0 Aac
Burden: 5 VA

Generator Voltage Drop

5% for 0.8 power factor load at 70% of nominal CT current
rating

UL Recognition

Standard 508, file number E75380

CSA Recognition

Standard CAN/CSA-C22.2, number 14-M91,
CSA file number LR23131

PHYSICAL SPECIFICATIONS

INTERCONNECTION

Current Sensing Input (Terminals C, 5A/1A)

Generator line current is sensed by either a 1 A or a 5 A (5
VA) secondary current transformer installed on the
generator B-phase output lead. The CT secondary should
deliver from 0.7 to 1 Aac for the 1 A tap or from 3.5 to 5
Aac for the 5 A tap when the generator is at rated load and
power factor. The CT develops a voltage signal across
adjustable resistor R1 in the Paralleling Module that is
proportional in amplitude and phase to the generator line
current. This voltage is applied to the primary of
transformer T1. The secondary of T1 is connected in series
with the voltage applied to the voltage regulator sensing
circuit. The result signal that is applied to the voltage
regulator sensing circuit is the vector sum of the generator
ac voltage and the voltage developed by the APM 2000.

Paralleling Signal Sensing Output (Terminals 6 and 7)

When a resistive load (at unity power factor) is applied to
the generator, the voltage that appears across R1 (and
transformer T1) leads the sensing voltage by 90 degrees.
Since the vector sum of these two voltages is nearly the
same as the original sensing voltage, almost no change will
occur in the generator output voltage.

When an inductive load (lagging power factor) is applied to
the generator, the voltage across R1 becomes more in
phase with the sensing voltage and the combined vectors
of the two voltages result in a larger voltage being applied
to the voltage regulator sensing circuit. Since the action of
the regulator is to maintain a constant voltage at its sensing
terminals, the voltage regulator reacts by decreasing
generator voltage.

When a capacitive load (leading power factor) is applied to
the generator, the voltage across R1 becomes out of phase
with the sensing voltage and the combined vectors of the
two voltages result in a smaller voltage being applied to the
voltage regulator sensing circuit. Since the action of the
regulator is to maintain a constant voltage at its sensing
terminals, the voltage regulator reacts by increasing
generator voltage.

Temperature

Operating: –55 to 70°C (–67 to 158°F)
Storage: –65 to 85°C (–85 to 185°F)

Weight

590 g (1.3 lb)

INSTALLATION

Mounting

The rugged construction of the APM 2000 Paralleling
Module permits mounting directly on the engine or genset.
It can also be mounted directly on the switchgear or control
panel. The APM 2000 may be mounted in any position
without affecting its operation. For mounting, see Figure 1.

Publication

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Revision

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PARALLEL COMPENSATION

When two generators are operating in parallel (Figures 2
and 3) the field excitation on one generator becomes
excessive, causing a circulating current to flow between
generators. The current appears as an inductive load to the
generator (lagging power factor) with excessive field
current and as a capacitive load to the other (leading power
factor). The reactive droop compensation circuit in the APM
2000 will cause the voltage regulator to decrease its field
excitation on the generator with the lagging power factor
load in order to minimize the circulating currents between
the generators.

This type of circuit is called reactive droop compensation. It
allows two or more paralleled generators to proportionally
share inductive loads by causing a decrease or droop in
the generator system voltage.

First Printing: 06/82

Revised: 10/03

Copyright

2003

The APM 2000 also provides the secondary circuit isolation
for reactive differential compensation operation (Figures 4
and 5). Reactive differential compensation allows two or
more paralleled generators in an isolated system to share
inductive, reactive loads with no decrease or droop in the
generator system output voltage. This is accomplished by
the action and circuitry described previously for reactive
droop compensation and by the cross connecting of the CT
secondary leads. The figures show the finish of the first CT
connected to the start of the second CT, etc. until all CTs
are connected in series. The final step is to connect the
finish of the last CT to the start of the first CT. This forms a
closed, series loop that interconnects the CTs of all
generators to be paralleled. The signals from the
interconnected CTs cancel each other when the line
currents are proportional and in phase and no drop in
system voltage occurs.

Reactive differential compensation can be used only if the
regulators are identical and if the regulators on all the
generators operating on a common bus are cross
connected into the closed series loop. Generators of
different kW ratings may be operated with reactive
differential compensation if parallel CTs are selected that
give approximately the same secondary current of each
generator's rated load.

In reactive differential compensation applications of more
than two generators, an external Unit-Parallel switch should
be placed across terminals 1A and C and set to the Unit
position when not operating on the load bus. If it is not, a
voltage drop will be introduced into the system. This is
because the unloaded generator parallel CT is not
supplying its compensating signal, but allowing a voltage
drop to occur across it. This drop will also cause the
voltage of the incoming generator to fluctuate prior to
paralleling. This fluctuation can be eliminated by utilizing an
auxiliary contact on the main generator circuit as a Unit­Parallel switch. This auxiliary contact will be closed when
the main generator circuit breaker closes. When this
auxiliary contact is closed, the Unit-Parallel switch is not
needed.

OPERATION

Before paralleling, the following test should be performed to
confirm that the correct polarity and phase relationship
exists between the voltage regulator, parallel current
transformer, and paralleling module. Repeat this test for all
systems that are to be paralleled.

If reactive differential compensation is used, the
interconnection loop between the generators should be left
open until completing these tests. (See Figures 4 and 5.)

NOTE
Meggers and high-potential test equipment should be
used with extreme care. Incorrect use of such
equipment could damage components contained in the
device.

1. Adjust R1 (APM 2000) to the maximum resistance
position (fully clockwise).

2. Set the Unit-Parallel switch to Unit or place a jumper
across terminals C and 1A.

3. With the generator operating at rated speed and
voltage, apply a lagging power factor load. (Unity
power factor load cannot be used for this test.) Record
the generator voltage.

4. With the load still applied, place the Unit-Parallel
switch in the Parallel position and record the generator
voltage.

5. Verify that the voltage obtained with the Unit-Parallel
switch set to Parallel is less than the voltage obtained
with the switch set to Unit.

6. If a higher voltage was obtained with the Unit-Parallel
switch set to Parallel, stop the system and verify that
the CT and sensing leads are connected to the correct
generator lines. If all connections are proper and
correct, interchange the parallel CT secondary leads.

7. If step 6 was required, repeat steps 1 through 4 to
ensure that the system voltage droop is obtained.

NOTE

During single-unit operation, the Unit-Parallel switch
shorts terminals C and 1A to prevent any droop signal
from being injected into the regulating system. The
system may be operated with the Unit-Parallel switch in
the Parallel position if the voltage droop that results
from the load is not objectionable.

REPLACEMENT PARTS

Table 1 lists the SPM 2000 components and assemblies
that have maintenance significance. When ordering parts
from Basler Electric, specify the APM 2000 part number
(9 1473 00 100), component reference designation,
component part number, and component description.

Table 1. Replacement Parts

Ref.

Des. Part Number Qty Description

R1 14855 1

S1* 02660 1 Switch

T1 BE19289-001 1 Transformer
* Unit-Parallel Switch S1 is not supplied with the APM 2000
and must be ordered separately.

Resistor, variable, 6Ω, 12.5W

Page 2 First Printing: 06/82

Revised: 10/03

Revision

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Publication

9 1473 00 990