MEC 20 MICROPROCESSOR ENGINE/GENERATOR CONTROLLER
PM047 Rev 13 05/03/30
7
Thomson Technology
must be “dry” (i.e. non-powered) and one side must be connected to the common DC
negative conductor.
2.5. AC VOLTAGE INPUT
The MEC 20 can accept direct AC voltage input from 120-600Vac (nominal).
Note:
Direct input voltage sensing can only be used when the generator utilizes a single
phase 3 wire or 3 phase, 4 wire distribution system with a solidly grounded neutral
conductor. For 3 phase 3 wire systems (i.e. no neutral) or high voltage systems,
potential transformers must be used. Refer to FIGURES #1 - 4 for voltage sensing
connections. To display generator line to neutral voltage in a 3 phase 4 wire system,
the neutral must be connected as shown.
GRD
MEC 20
FIGURE #1
3Ø, 4W 208/380/480/600VAC DIRECT SENSING
SOLIDLY GROUNDED NEUTRAL SYSTEM
VOLTAGE INPUTS
600VAC L-L, 347VAC L-N
380VAC L-L, 220VAC L-N
480VAC L-L, 277VAC L-N
208VAC L-L, 120VAC L-N
VA
VB
VC
VN
GRD
B
A
C
N
GEN.
GRD
A
B
C
N
GRD
MEC 20
FIGURE #2
1Ø, 3W 120/240VAC DIRECT SENSING
SOLIDLY GROUNDED NEUTRAL SYSTEM
VOLTAGE INPUTS
240VAC L-L, 120VAC L-N
Note:
L1 and L2 phase
voltages must be 120Vac
when referenced to common
neutral. (Delta connected
generators required PTs as per
figure#3 & no phase C PT)
VA
VB
VC
VN
GRD
L2
L1
N
GEN.
GRD
L1 L2
N
No Connection
GRD
MEC 20
FIGURE #3
3Ø, 4W WYE PT's
SECONDARY PT VOLTAGE
208VAC L-L, 120VAC L-N
120VAC L-L, 69VAC L-N
VA
VB
VC
VN
GRD
B
A
C
N
GEN.
N
120
120
120
GRD
A
B
C
GRD
MEC 20
FIGURE #4
3Ø, 3W DELTA PT's
SECONDARY PT VOLTAGE
120VAC L-L
(NO NEUTRAL)
VA
VB
VC
VN
GRD
120
120
GRD
B
A
C
GEN.
A
B
C
N
No Connection
G:\ENGINEER\PRODUCTS\MEC20\MEC20_08.VSD REV. 2 02/02/22
Summary of Contents for MEC 20
Page 2: ......
Page 6: ...MEC 20 MICROPROCESSOR ENGINE GENERATOR CONTROLLER...
