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Ref: PLL/D APR11-REV1 
 

Installation and Operating

Instructions

Page 1 of 2 

 

Synchro-check Monitor PLL/D-100/120, PLL/D-173/240,  
PLL/D-380/480, PLL/D-277/500 DIN-rail mounted 

  

Introduction 

This unit compares the voltage, frequency and phase angle of two 
supplies and operates a relay according to the synchronicity of the 
supplies.  If the two supplies cease to match, the relay operates to 
provide a control output.  The relay output can be used for alarm or 
control purposes.  

The unit also provides a dead bus function.  If the bus supply fails, the 
relay operates and the output can be used to switch in an emergency 
generator.  LEDs indicate power on, relay and dead bus status. 
Controls on the front panel set the trip points at which the relays and 
LEDs operate: 

 

Degree of synchronicity Ux (%Volts)   

 

Nominal voltage (Un) 

 

Dead bus function on/off 

The unit is powered from the generator supply.   
These instructions contain important safety information. Please read 
them thoroughly before commissioning, operating or maintenance of 
the unit. 

Specification 

Parameter   

PLL/PLD

 

100/120 173/240 380/480 277/500 

Rated Vg range Un 

57-69V 

100-

139V 

220-

277V 

277-

500V 

Overload capacity 

- continuous 

 

87V 

 

174V 

 

346V 

 

600V 

- 10s max. 

104V 

209V 

416V 

700V 

Minimum supply Vg Uon 

35V 

60V 

132V 

166V 

Burden on supply (Max) 

2 VA / 

1.6W 

2.7 VA / 

1.7W 

4 VA / 

2.2W 

5 VA / 

2.8W 

Frequency range 

45-65 Hz 

Deadbus on Udbon 

25% Uon 

Deadbus off Udboff 

50% Uon 

Sync Tolerance 

10-30% Volts 

Relay contacts:

 for 

general switching 

 

2 x changeover, volt-free 

Load capacity - a.c. 

250V @ 8A, 2 kVA 

Load capacity - d.c. 

30V 8A 

Insulation 

4 kV/1 min 

Mech. endurance 

30x10

6

 operations 

Other Data: 

 

Dimensions 

90 x 105 x 64 mm 

Weight 

(100/208/380/277)

 

291 / 335 / 332 / 335 g 

Maximum conductor 
size  

2 x 1.5 mm

or 1 x 2.5 mm

2

 

Operating temperature 

-20 to +55 °C 

Storage temperature 

-30 to +70 °C 

Over-voltage category 

III 

Pollution degree 

Environmental 
protection 

IP40 for front panel 

IP20 for terminals. 

Standards 

EN 60255-6, EN 60255-27, EN 61000-6-2, 

EN 61000-6-4 

  

Insulation Class: Ensure any external circuits connected to the 
relay are provided with double or reinforced insulation. 

Operation 

The green 

 LED lights shows when the power supply is on. 

While the two supplies match in voltage, frequency and phase to the 
degree set by the %Volts control, the 

Sync

 LED lights and the relay is 

energised. 
If one supply varies such that they no longer match to that degree, the 

Sync

 LED goes off and the relay de-energises.   

If the generator voltage falls below the Uon level, the unit ceases to 
operate, the relay de-energises and the 

Sync

 LED goes off. 

With Dead Bus On, if the bus voltage falls below the Udbon level, the 
relay energises and the 

Dead Bus

 LED lights.  The relay can be used 

to turn on an emergency supply in the event of bus supply failure.  The 
relay will de-energise again and the LED will go off when the bus 
voltage rises above the Udboff level. 
 

Note; Red LED indicates fault condition, not relay status 

 

Installation 

The unit is intended for mounting on a standard DIN rail.  Hook the unit 
onto the top of the rail and press the bottom of the unit until it locks in 
place.  To remove the unit from the rail, lever down the black tabs at 
the bottom of the unit to release it from the rail. 
The unit is intended for use in a reasonably stable ambient 
temperature within the range -20 to +55°C.  Do not mount the unit 
where there is excessive vibration or in excessive direct sunlight. 
 

 

 

The differential trip levels help to prevent relay chatter as the 
monitored voltage level varies. 
As the relays have changeover contacts, the relay outputs can be 
inverted by wiring to the alternative terminals 15-16 or 25-26. 

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